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Ultraviolet spectroscopy of Comet Austin (1989c1) using a two-dimensional diode array detector
NASA Astrophysics Data System (ADS)
Sahnow, David James
A two-dimensional, photon-counting intensified photodiode array detector has been constructed and successfully tested in the laboratory and on a spectrograph in three sounding rocket flights. The detector is an extension of the one-dimensional intensified diode array detector used in the Hopkins Ultraviolet Telescope. Extensive laboratory measurements have shown that it can successfully centroid with sub-diode resolution, and can be used in place of ranicon detectors to measure the spectra of faint objects. The instrument successfully obtained long slit far-ultraviolet spectra (1250-1850 A) of Comet Austin (1989 c1) on 21 April 1990. Emissions of OI, CI, SI and CO were detected during the 270 seconds of data acquisition. The spectral resolution was 5.5 A, while the spatial resolution was limited by pointing jitter to approximately 30 arcseconds. The spatial profiles of the carbon and oxygen emissions show narrow enhancements which are suggestive of a cometary outburst which occurred 15-20 hours before the observation. The overall shape of the atomic carbon profile is similar to those measured during two observations of Comet Halley (1986 III), and is similarly incompatible with photodissociation of CO as its primary source, as determined by model calculations. The CO profile, however, is consistent with that of a parent molecule evaporating directly from the nucleus, with a production rate of 4 plus or minus 1 x 1027 molecules s-1. The O I lambda 1304 emission, also similar in spatial shape to that detected in Halley, includes a contribution due to Bowen fluorescence induced by solar HI Lyman-beta, and its profile can be understood as that due to the photodissociation of H2O, with a production rate of 6.2 plus or minus 0.3 x 1028 molecules s-1, giving an abundance of CO relative to water of 6.5 percent. Spatial profiles of SI lambda 1814 were also obtained, with profiles attributable to that of a daughter product of short-lived species such as CS2 and H2S.
Determination of flavone C-glucosides in antioxidant of bamboo leaves (AOB) fortified foods by reversed-phase high-performance liquid chromatography with ultraviolet diode array detection
Yu Zhang; Bili Bao; Boyi Lu; Yiping Ren; Xiaowei Tie; Ying Zhang
Reversed-phase high-performance liquid chromatography (RP-HPLC) with ultraviolet diode array detection (UV-DAD) was used for the simultaneous determination of four flavone C-glucosides, i.e. orientin, homoorientin, vitexin and isovitexin in several food systems fortified by the antioxidant of bamboo leaves (AOB), such as high temperature sterilized milk, sunflower seed oil and extruded rice cake for the first time. The method included extraction
Enhanced ultraviolet emission and improved spatial distribution uniformity of ZnO nanorod array light-emitting diodes via Ag nanoparticles decoration.
Liu, Wei Zhen; Xu, Hai Yang; Wang, Chun Liang; Zhang, Li Xia; Zhang, Cen; Sun, Shi Yu; Ma, Jian Gang; Zhang, Xin Tong; Wang, Jian Nong; Liu, Yi Chun
Localized surface plasmon (LSP) enhanced ultraviolet (UV) light-emitting diodes (LEDs) were fabricated by embedding a ZnO nanorod array/p-GaN film heterostructure into a Ag-nanoparticles/PMMA composite. By optimizing the concentration of Ag nanoparticles in PMMA, two distinct changes in electroluminescence (EL) spectra were observed: (1) the UV EL component from ZnO excitons was selectively enhanced more than 13-fold and the entire spectral lineshape was changed and (2) the spatial uniformity of the output photon intensity was improved and the linewidth of an angular distribution curve was increased by ?2 times. These observations can be attributed to near-field optical coupling between Ag LSPs and ZnO excitons. Time-resolved luminescence measurements and a model calculation reveal that the optical coupling results in the increase of the spontaneous emission rate and internal quantum efficiency of Ag-nanoparticles-decorated ZnO nanorod arrays. Moreover, the LSP-exciton interaction allows the device's EL to be coupled out of the nanorod waveguide and to be isotropically scattered into every direction, thus broadening the angular distribution of the EL intensity. PMID:23897294
NASA Technical Reports Server (NTRS)
Carlson, Nils W. (Inventor); Evans, Gary A. (Inventor); Kaiser, Charlie J. (Inventor)
A diode laser array comprises a substrate of a semiconductor material having first and second opposed surfaces. On the first surface is a plurality of spaced gain sections and a separate distributed Bragg reflector passive waveguide at each end of each gain section and optically connecting the gain sections. Each gain section includes a cavity therein wherein charge carriers are generated and recombine to generate light which is confined in the cavity. Also, the cavity, which is preferably a quantum well cavity, provides both a high differential gain and potentially large depth of loss modulation. Each waveguide has a wavelength which is preferably formed by an extension of the cavity of the gain sections and a grating. The grating has a period which provides a selective feedback of light into the gain sections to supporting lasing, which allows some of the light to be emitted from the waveguide normal to the surface of the substrate and which allows optical coupling of the gain sections. Also, the grating period provides an operating wavelength which is on the short wavelength side of the gain period of the gain sections required for laser oscillation. An RF pulse is applied so as to maximize the magnitude of the loss modulation and the differential gain in the gain sections. The array is operated by applying a DC bias to all the gain sections at a level just below the threshold of the gain sections to only one of the gain sections which raises the bias in all of the gain sections to a level that causes all of the gain sections to oscillate. Thus, a small bias can turn the array on and off.
Simultaneous determination three phytosterol compounds, campesterol, stigmasterol and daucosterol in Artemisia apiacea by high performance liquid chromatography-diode array ultraviolet/visible detector
Lee, Jiwoo; Weon, Jin Bae; Yun, Bo-Ra; Eom, Min Rye; Ma, Choong Je
Background: Artemisia apiacea is a traditional herbal medicine using treatment of eczema and jaundice in Eastern Asia, including China, Korea, and Japan. Objective: An accurate and sensitive analysis method using high performance liquid chromatography-diode array ultraviolet/visible detector and liquid chromatography¢mass spectrometry for the simultaneous determination of three phytosterol compounds, campesterol, stigmasterol and daucosterol in A. apiacea was established. Materials and Methods: The analytes were separated on a Shiseido C18 column (5 ?m, 4.6 mm I.D. ū250 mm) with gradient elution of 0.1% trifluoroacetic acid and acetonitrile. The flow rate was 1 mL/min and detection wavelengths were set at 205 and 254 nm. Results: Validation of the method was performed to demonstrate its linearity, precision and accuracy. The calibration curves showed good linearity (R2 > 0.9994). The limits of detection and limits of quantification were within the ranges 0.55¢7.07 ?g/mL and 1.67¢21.44 ?g/mL, respectively. And, the relative standard deviations of intra- and inter-day precision were <2.93%. The recoveries were found to be in the range of 90.03¢104.91%. Conclusion: The developed method has been successfully applied to the analysis for quality control of campesterol, stigmasterol and daucosterol in A. apiacea. PMID:25829768
Qualitative characterization of Desmodium adscendens constituents by high-performance liquid chromatography-diode array ultraviolet-electrospray ionization multistage mass spectrometry.
Baiocchi, Claudio; Medana, Claudio; Giancotti, Valeria; Aigotti, Riccardo; Dal Bello, Frederica; Massolino, Cristina; Gastaldi, Daniela; Grandi, Maurizio
The many effects of the African medicinal herb Desmodium adscendens were studied in the 1980s and 1990s. In spite of this, a comprehensive analytical protocol for the quality control of its constituents (soyasaponins, alkaloids and flavonoids) has not yet been formulated and reported. This study deals with the optimization of extraction conditions from the plant and qualitative identification of the constituents by HPLC-diode array UV and multistage mass spectrometry. Plant constituents were extracted from leaves by liquid-liquid and solid matrix dispersion extraction. Separation was achieved via RP-C18 liquid chromatographywith UV and MS(n) detection and mass spectrometry analysis was conducted by electrospray ionization ion trap or orbitrap mass spectrometry. High resolution mass spectrometry (HRMS) was used for structural identification of active molecules relating to soyasaponins and alkaloids. The flavonoid fragmentations were preliminarily studied by HRMS in order to accurately characterize the more common neutral losses. However, the high number of isomeric species induced us to make recourse to a more extended chromatographic separation in order to enable useful tandem mass spectrometry and ultraviolet spectral interpretation to propose a reasonable chemical classification of these polyphenols. 35 compounds of this class were identified herein with respect to the five reported in literature in this way we made up a comprehensive protocol for the qualitative analysis of the high complexity content of this plant. This result paves the way for both reliable quality control of potential phytochemical medicaments and possible future systematic clinical studies. PMID:23841221
Deep-Ultraviolet Light-Emitting Diodes
Michael S. Shur; Remis Gaska
Compact solid-state deep-ultraviolet (DUV) light-emitting diodes (LEDs) go far beyond replacing conventional DUV sources such as mercury lamps. DUV LEDs enable new applications for air, water, and surface sterilization and decontamination, bioagent detection and identification, UV curing, and biomedical and analytical instrumentation. We review materials growth, device physics, design, fabrication, and performance of DUV LEDs with wavelength ranging from 210
Diode-Laser Array Suppresses Extraneous Modes
NASA Technical Reports Server (NTRS)
Kapon, Elyahou; Lindsey, Chris P.; Katz, Joseph; Margalit, Shlomo; Yariv, Amnon
Diode parameters varied to shape output beam. Array of phase-locked GaAs/GaAIAs diode lasers produces light beam with one main radiation lobe. Physical parameters of laser diodes differ from each other in way that favors oscillation in fundamental supermode, suppressing oscillation in higher-order modes.
International ultraviolet explorer solar array power degradation
J. H. Day Jr.
The characteristic electrical performance of each International Ultraviolet Explorer (IUE) solar array panel is evaluated as a function of several prevailing variables (namely, solar illumination, array temperature and solar cell radiation damage). Based on degradation in the current-voltage characteristics of the array due to solar cell damage accumulated over time by space charged particle radiations, the available IUE solar array
Enhanced waveguide-type ultraviolet electroluminescence from ZnO/MgZnO core/shell nanorod array light-emitting diodes via coupling with Ag nanoparticles localized surface plasmons
NASA Astrophysics Data System (ADS)
Zhang, Cen; Marvinney, Claire Elizabeth; Xu, Hai Yang; Liu, Wei Zhen; Wang, Chun Liang; Zhang, Li Xia; Wang, Jian Nong; Ma, Jian Gang; Liu, Yi Chun
Localized surface plasmon (LSP) enhanced waveguide-type ultraviolet light-emitting diodes (LEDs) were fabricated by sputtering Ag nanoparticles (Ag-NPs) onto ZnO/MgZnO core/shell nanorod array (CS-NRA)/p-GaN heterostructures. A ~9-fold enhancement of ZnO ultraviolet electroluminescence (EL) was demonstrated by the Ag-NPs decorated LED compared with the device without Ag-NPs. Angle-dependent EL measurements, as well as finite-difference time-domain simulations of the EL intensity spatial distribution, confirmed the waveguide-type EL transmission mode along the NR's axial direction. The increased spontaneous emission rate observed in time-resolved spectroscopy suggested that the ZnO EL enhancement was attributed to LSP-exciton/polariton coupling. However, a direct coupling is very difficult to achieve between Ag-LSPs and electron-hole pairs in the active region due to their ``remote'' separation. Thereby, two possible models involving the dynamic process of interactions among excitons, photons, and LSPs, were established to understand the selective enhancement of ZnO EL.Localized surface plasmon (LSP) enhanced waveguide-type ultraviolet light-emitting diodes (LEDs) were fabricated by sputtering Ag nanoparticles (Ag-NPs) onto ZnO/MgZnO core/shell nanorod array (CS-NRA)/p-GaN heterostructures. A ~9-fold enhancement of ZnO ultraviolet electroluminescence (EL) was demonstrated by the Ag-NPs decorated LED compared with the device without Ag-NPs. Angle-dependent EL measurements, as well as finite-difference time-domain simulations of the EL intensity spatial distribution, confirmed the waveguide-type EL transmission mode along the NR's axial direction. The increased spontaneous emission rate observed in time-resolved spectroscopy suggested that the ZnO EL enhancement was attributed to LSP-exciton/polariton coupling. However, a direct coupling is very difficult to achieve between Ag-LSPs and electron-hole pairs in the active region due to their ``remote'' separation. Thereby, two possible models involving the dynamic process of interactions among excitons, photons, and LSPs, were established to understand the selective enhancement of ZnO EL. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04966g
Enhanced waveguide-type ultraviolet electroluminescence from ZnO/MgZnO core/shell nanorod array light-emitting diodes via coupling with Ag nanoparticles localized surface plasmons.
Zhang, Cen; Marvinney, Claire Elizabeth; Xu, Hai Yang; Liu, Wei Zhen; Wang, Chun Liang; Zhang, Li Xia; Wang, Jian Nong; Ma, Jian Gang; Liu, Yi Chun
Localized surface plasmon (LSP) enhanced waveguide-type ultraviolet light-emitting diodes (LEDs) were fabricated by sputtering Ag nanoparticles (Ag-NPs) onto ZnO/MgZnO core/shell nanorod array (CS-NRA)/p-GaN heterostructures. A ?9-fold enhancement of ZnO ultraviolet electroluminescence (EL) was demonstrated by the Ag-NPs decorated LED compared with the device without Ag-NPs. Angle-dependent EL measurements, as well as finite-difference time-domain simulations of the EL intensity spatial distribution, confirmed the waveguide-type EL transmission mode along the NR's axial direction. The increased spontaneous emission rate observed in time-resolved spectroscopy suggested that the ZnO EL enhancement was attributed to LSP-exciton/polariton coupling. However, a direct coupling is very difficult to achieve between Ag-LSPs and electron-hole pairs in the active region due to their "remote" separation. Thereby, two possible models involving the dynamic process of interactions among excitons, photons, and LSPs, were established to understand the selective enhancement of ZnO EL. PMID:25475883
Frequency-narrowed diode array bar.
Babcock, Earl; Chann, Bien; Nelson, Ian A; Walker, Thad G
We describe a method to frequency narrow multielement high-power diode bars. Using a commercial 60-W, 49-element, 1-cm-long diode array bar at 795 nm running at 45 W, we narrow the linewidth from 1000 to 64 GHz with only a loss of 33% in output power. The resulting laser light is well suited for spin-exchange optical pumping of noble gas nuclei. PMID:15929304
International ultraviolet explorer solar array power degradation
NASA Technical Reports Server (NTRS)
Day, J. H., Jr.
The characteristic electrical performance of each International Ultraviolet Explorer (IUE) solar array panel is evaluated as a function of several prevailing variables (namely, solar illumination, array temperature and solar cell radiation damage). Based on degradation in the current-voltage characteristics of the array due to solar cell damage accumulated over time by space charged particle radiations, the available IUE solar array power is determined for life goals up to 10 years. Best and worst case calculations are normalized to actual IUE flight data (available solar array power versus observatory position) to accurately predict the future IUE solar array output. It is shown that the IUE solar array can continue to produce more power than is required at most observatory positions for at least 5 more years.
Narrow-Bandwidth Diode-Laser-Based Ultraviolet Light Source
Yu Peng; Zhan-Jun Fang; Er-Jun Zang
A compact, tunable and narrow-bandwidth laser source for ultraviolet radiation is presented. A grating stabilized diode laser at 1064 nm is frequency-stabilized to below 10 kHz by using a ultra low expansion (ULE) cavity. Injecting light of the diode laser into a tapered amplifier yields a power of 290 mW. In a first frequency-doubling stage, about 47 mW of green
The Fuge Tube Diode Array Spectrophotometer
ERIC Educational Resources Information Center
Arneson, B. T.; Long, S. R.; Stewart, K. K.; Lagowski, J. J.
We present the details for adapting a diode array UV-vis spectrophotometer to incorporate the use of polypropylene microcentrifuge tubes--fuge tubes--as cuvettes. Optical data are presented validating that the polyethylene fuge tubes are equivalent to the standard square cross section polystyrene or glass cuvettes generally used inģ
Graphene/GaN diodes for ultraviolet and visible photodetectors
Lin, Fang; Chen, Shao-Wen; Meng, Jie; Tse, Geoffrey; Fu, Xue-Wen; Xu, Fu-Jun [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China); Shen, Bo; Liao, Zhi-Min, E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com; Yu, Da-Peng, E-mail: email@example.com, E-mail: email@example.com [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)
The Schottky diodes based on graphene/GaN interface are fabricated and demonstrated for the dual-wavelength photodetection of ultraviolet (UV) and green lights. The physical mechanisms of the photoelectric response of the diodes with different light wavelengths are different. For UV illumination, the photo-generated carriers lower the Schottky barrier and increase the photocurrent. For green light illumination, as the photon energy is smaller than the bandgap of GaN, the hot electrons excited in graphene via internal photoemission are responsible for the photoelectric response. Using graphene as a transparent electrode, the diodes show a ?mS photoresponse, providing an alternative route toward multi-wavelength photodetectors.
Graphene/GaN diodes for ultraviolet and visible photodetectors
NASA Astrophysics Data System (ADS)
Lin, Fang; Chen, Shaowen; Meng, Jie; Tse, Geoffrey; Fu, Xuewen; Xu, Fujun; Shen, Bo; Liao, Zhimin; Yu, Dapeng; Nanolab Team
The Schottky diodes based on graphene/GaN interface are fabricated and demonstrated for the dual-wavelength photodetection of ultraviolet (UV) and green lights. The physical mechanisms of the photoelectric response of the diodes with different light wavelengths are different. For UV illumination, the photo-generated carriers lower the Schottky barrier and increase the photocurrent. For green light illumination, as the photon energy is smaller than the bandgap of GaN, the hot electrons excited in graphene via internal photoemission are responsible for the photoelectric response. Using graphene as a transparent electrode, the diodes show a ~ mS photoresponse, providing an alternative route toward multi-wavelength photodetectors.
Ultraviolet photoresponse characteristics of diamond diodes
NASA Astrophysics Data System (ADS)
Marchywka, M.; Goldberg, R. T.; Hochedez, J. F.; Geis, M. W.; Socker, D. G.; Moses, D.
It is suggested that the passive diamond surface should allow a stable VUV response, thus eliminating a serious shortcoming of existing solid-state VUV detectors. The mechanical superiority and electrical similarity of diamond compared to silicon suggest that 2D imagers of this type may be feasible. Three different devices were investigated: an Al-diamond Schottky diode, and two structures believed to be np diodes. Photoresponse measurements were made, and favorable results were obtained.
Ultraviolet nanoimprinted polymer nanostructure for organic light emitting diode application
Sohee Jeon; Jae-Wook Kang; Hyung-Dol Park; Jang-Joo Kim; Jae R. Youn; Jongyoup Shim; Jun-Ho Jeong; Dae-Geun Choi; Ki-Don Kim; Ali Ozhan Altun; Se-Heon Kim; Yong-Hee Lee
Light extraction efficiency of a conventional organic light emitting diode (OLED) remains limited to approximately 20% as most of the emission is trapped in the waveguide and glass modes. An etchless simple method was developed to fabricate two-dimensional nanostructures on glass substrate directly by using ultraviolet (UV) curable polymer resin and UV nanoimprint lithography in order to improve output coupling
A 4ū4 active array using Gunn diodes
R. A. York; R. C. Compton
The authors present results from a new 16-element active array incorporating Gunn diodes (for 10 GHz oscillations). The Gunn diode heating problem previously encountered was overcome by using patch antennas in which the ground plane serves as a diode heat sink. An EIRP (equivalent isotropic radiated power) of 22 W was measured for this array. It is suggested that, by
Freitas, B.L.; Skidmore, J.A.
A substrate is used to fabricate a low-cost laser diode array. A substrate is machined from an electrically insulative material that is thermally conductive, or two substrates can be bonded together in which the top substrate is electrically as well as thermally conductive. The substrate thickness is slightly longer than the cavity length, and the width of the groove is wide enough to contain a bar and spring (which secures the laser bar firmly along one face of the groove). The spring also provides electrical continuity from the backside of the bar to the adjacent metalization layer on the laser bar substrate. Arrays containing one or more bars can be formed by creating many grooves at various spacings. Along the groove, many bars can be adjoined at the edges to provide parallel electrical conduction. This architecture allows precise and predictable registration of an array of laser bars to a self-aligned microlens array at low cost. 19 figs.
Freitas, Barry L. (Livermore, CA); Skidmore, Jay A. (Livermore, CA)
A substrate is used to fabricate a low-cost laser diode array. A substrate is machined from an electrically insulative material that is thermally conductive, or two substrates can be bonded together in which the top substrate is electrically as well as thermally conductive. The substrate thickness is slightly longer than the cavity length, and the width of the groove is wide enough to contain a bar and spring (which secures the laser bar firmly along one face of the groove). The spring also provides electrical continuity from the backside of the bar to the adjacent metalization layer on the laser bar substrate. Arrays containing one or more bars can be formed by creating many grooves at various spacings. Along the groove, many bars can be adjoined at the edges to provide parallel electrical conduction. This architecture allows precise and predictable registration of an array of laser bars to a self-aligned microlens array at low cost.
VBG controlled narrow bandwidth diode laser arrays
NASA Astrophysics Data System (ADS)
Levy, Joseph; Feeler, Ryan; Junghans, Jeremy
Northrop Grumman Cutting Edge Optronics has developed large kilowatt class lensed laser diode arrays with subnanometer spectral width using Volume Bragg Grating (VBG) reflectors. Using these CW arrays with 100W bars at 885nm, excellent absorption in Nd:YAG is achieved, with lower thermal aberration than can be attained with 808nm pumps. The additional cost of the VBG reflectors and their alignment is partially offset by the much broader wavelength tolerance that is allowed in the unlocked array enhancing bar yield. Furthermore, the center wavelength of the arrays exhibit lower temperature sensitivity allowing the arrays to be operated over a wider current or temperature range than arrays without wavelength control. While there is an efficiency penalty associated with the addition of VBGs of 5-8%, it is more than compensated for by enhanced absorption, especially when used with narrowband absorption lines, such as 885nm in Nd:YAG. An overview of the design and manufacturing issues for arrays that are wavelength-locked with VBGs is presented along with the effect of post-construction hard UV exposure.
Tunnel Diode Arrays for Information Processing and Storage
Alwyn C. Scott
The multimode oscillator properties of two-dimensional arrays of tunnel diode elements are analyzed in the quasi-harmonic approximation with the assumption of no resonant interaction between the normal modes in order to determine the capacity of an array for information storage. Experimental results for a 4 ?? 4 array of semiconductor tunnel diodes are discussed, and suggestions for possible future information
Passive intrinsic-linewidth narrowing of ultraviolet extended-cavity diode laser
Vuletic, Vladan
Passive intrinsic-linewidth narrowing of ultraviolet extended-cavity diode laser by weak optical linewidth of a commercial ultraviolet grating extended-cavity diode laser (TOPTICA DL Pro) using weak stabilization; (140.2020) Diode lasers; (140.3610) Lasers, ul- traviolet. References and links 1. L. Ricci, M
Microlens frames for laser diode arrays
Skidmore, Jay A. (Livermore, CA); Freitas, Barry L. (Livermore, CA)
Monolithic microlens frames enable the fabrication of monolithic laser diode arrays and are manufactured inexpensively with high registration, and with inherent focal length compensation for any lens diameter variation. A monolithic substrate is used to fabricate a low-cost microlens array. The substrate is wet-etched or sawed with a series of v-grooves. The v-grooves can be created by wet-etching, by exploiting the large etch-rate selectivity of different crystal planes. The v-grooves provide a support frame for either cylindrical or custom-shaped microlenses. Because the microlens frames are formed by photolithographic semiconductor batch-processing techniques, they can be formed inexpensively over large areas with precise lateral and vertical registration. The v-groove has an important advantage for preserving the correct focus for lenses of varying diameter.
Silicon monolithic microchannel-cooled laser diode array
NASA Astrophysics Data System (ADS)
Skidmore, J. A.; Freitas, B. L.; Crawford, J.; Satariano, J.; Utterback, E.; DiMercurio, L.; Cutter, K.; Sutton, S.
A monolithic microchannel-cooled laser diode array is demonstrated that allows multiple diode-bar mounting with negligible thermal cross talk. The heat sink comprises two main components: a wet-etched Si layer that is anodically bonded to a machined glass block. The continuous wave (cw) thermal resistance of the 10 bar diode array is 0.032 ░C/W, which matches the performance of discrete microchannel-cooled arrays. Up to 1.5 kW/cm2 is achieved cw at an emission wavelength of ś808 nm. Collimation of a diode array using a monolithic lens frame produced a 7.5 mrad divergence angle by a single active alignment. This diode array offers high average power/brightness in a simple, rugged, scalable architecture that is suitable for large two-dimensional areas.
Space Qualification of Laser Diode Arrays
NASA Technical Reports Server (NTRS)
Troupaki, Elisavet; Kashem, Nasir B.; Allan, Graham R.; Vasilyev, Aleksey; Stephen, Mark
Laser instruments have great potential in enabling a new generation of remote-sensing scientific instruments. NASA s desire to employ laser instruments aboard satellites, imposes stringent reliability requirements under severe conditions. As a result of these requirements, NASA has a research program to understand, quantify and reduce the risk of failure to these instruments when deployed on satellites. Most of NASA s proposed laser missions have base-lined diode-pumped Nd:YAG lasers that generally use quasi-constant wave (QCW), 808 nm Laser Diode Arrays (LDAs). Our group has an on-going test program to measure the performance of these LDAs when operated in conditions replicating launch and orbit. In this paper, we report on the results of tests designed to measure the effect of vibration loads simulating launch into space and the radiation environment encountered on orbit. Our primary objective is to quantify the performance of the LDAs in conditions replicating those of a satellite instrument, determine their limitations and strengths which will enable better and more robust designs. To this end we have developed a systematic testing strategy to quantify the effect of environmental stresses on the optical and electrical properties of the LDA.
Tunable picosecond blue and ultraviolet pulses from a diode-pumped laser system seeded
Paris-Sud XI, Universitķ de
Tunable picosecond blue and ultraviolet pulses from a diode-pumped laser system seeded by a gain-switched laser diode FrancĖ ois Balembois, Mickae© l Gaignet, Patrick Georges, Alain Brun, Nikolai© Stelmakh, and Jean Michel Lourtioz Picosecond pulses emitted from a gain-switched laser diode have been amplified
Rubidium vapor laser pumped by two laser diode arrays.
Zhdanov, Boris V; Stooke, Adam; Boyadjian, Gregory; Voci, Adam; Knize, R J
Scaling of alkali lasers to higher powers requires using multiple diode lasers for pumping. The first (to our knowledge) results of a cw rubidium laser pumped by two laser diode arrays are presented. A slope efficiency of 53%, total optical efficiency of 46%, and output power of 17 W have been demonstrated. PMID:18311276
Means for phase locking the outputs of a surface emitting laser diode array
NASA Astrophysics Data System (ADS)
Lesh, James R.
An array of diode lasers, either a two-dimensional array of surface emitting lasers, or a linear array of stripe lasers, is phase locked by a diode laser through a hologram which focuses the output of the diode laser into a set of distinct, spatially separated beams, each one focused onto the back facet of a separate diode laser of the array. The outputs of the diode lasers thus form an emitted coherent beam out of the front of the array.
Modular package for cooling a laser diode array
Mundinger, David C. (Stockton, CA); Benett, William J. (Livermore, CA); Beach, Raymond J. (Livermore, CA)
A laser diode array is disclosed that includes a plurality of planar packages and active cooling. The laser diode array may be operated in a long duty cycle, or in continuous operation. A laser diode bar and a microchannel heat sink are thermally coupled in a compact, thin planar package having the laser diode bar located proximate to one edge. In an array, a number of such thin planar packages are secured together in a stacked configuration, in close proximity so that the laser diodes are spaced closely. The cooling means includes a microchannel heat sink that is attached proximate to the laser bar so that it absorbs heat generated by laser operation. To provide the coolant to the microchannels, each thin planar package comprises a thin inlet manifold and a thin outlet manifold connected to an inlet corridor and an outlet corridor. The inlet corridor comprises a hole extending through each of the packages in the array, and the outlet corridor comprises a hole extending through each of the packages in the array. The inlet and outlet corridors are connected to a conventional coolant circulation system. The laser diode array with active cooling has application as an optical pump for high power solid state lasers. Further, it can be incorporated in equipment such as communications devices and active sensors, and in military and space applications, and it can be useful in applications having space constraints and energy limitations.
PIN diode array x-ray imaging. Final Technical report
Jernigan, J.G. [Space Sciences Laboratory, California Univ., Berkeley, CA (United States)
We have completed constructing an x-ray camera based on a solid state imaging device and have obtained images of Omega laser targets. A Si PIN diode array is used. Objective of this project is to investigate the use of a PIN diode array readout device for obtaining images of 1-20 keV x-ray emission from laser targets. The PIN array detector was successfully used for obtaining hard x-ray images in the high powered laser environment and real time images of the x-ray emission from laser targets.
Microchannel heatsinks for high average power laser diode arrays
Beach, R.; Benett, B.; Freitas, B.; Ciarlo, D.; Sperry, V.; Comaskey, B.; Emanuel, M.; Solarz, R.; Mundinger, D.
Detailed performance results and fabrication techniques for an efficient and low thermal impedance laser diode array heatsink are presented. High duty factor or even CW operation of fully filled laser diode arrays is enabled at high average power. Low thermal impedance is achieved using a liquid coolant and laminar flow through microchannels. The microchannels are fabricated in silicon using a photolithographic pattern definition procedure followed by anisotropic chemical etching. A modular rack-and-stack architecture is adopted for the heatsink design allowing arbitrarily large two-dimensional arrays to be fabricated and easily maintained. The excellent thermal control of the microchannel cooled heatsinks is ideally suited to pump array requirements for high average power crystalline lasers because of the stringent temperature demands that result from coupling the diode light to several nanometers wide absorption features characteristic of leasing ions in crystals.
Ultraviolet Light Emitting Diodes and Bio-Aerosol Sensing Kristina M. Davitt
Davitt, Kristina
Ultraviolet Light Emitting Diodes and Bio-Aerosol Sensing by Kristina M. Davitt B. Sc. Queen in the field of bio-aerosol sensing. These collaborations have all been supported under the DARPA SUVOS program
Chirped arrays of diode lasers for supermode control
NASA Technical Reports Server (NTRS)
Kapon, E.; Lindsey, C.; Margalit, S.; Yariv, A.; Katz, J.
Nonuniform structures of phase-locked diode lasers, which make it possible to discriminate efficiently against all the higher order array supermodes (lateral modes) are proposed. In these nonuniform arrays, the effective mode index in each channel varies across the array. Consequently, the envelopes of the various supermodes, including the highest order one, differ significantly from each other. Thus, by proper tailoring of the gain distribution across the array, one can conveniently select the fundamental supermode. Such fundamental supermode oscillation is essential in order to obtain single lobe, diffraction limited beams and minimal spectal spread from phase-locked laser arrays.
Light emitting diode arrays for consumer and medical applications
Andrew Rys; Tadeusz Piotrowski; Radoslaw Sobczynski
Development of light emitting diodes (LEDs) and arrays of diodes to be utilized in a modern and highly sensitive spectrophotometer is presented. The In1?xGaxAs1?yPy quaternary alloy semiconductor has been utilized in the design and fabrication of surface emitting infrared LEDs in the spectral range from 1100 to 1650 nm. Custom made chips provide the surface-emitting LEDs with high radiance and
Applications of microlens-conditioned laser diode arrays
Beach, R.J.; Emanuel, M.A.; Freitas, B.L. [and others
The ability to condition the radiance of laser diodes using shaped-fiber cylindrical-microlens technology has dramatically increased the number of applications that can be practically engaged by diode laser arrays. Lawrence Livermore National Laboratory (LLNL) has actively pursued optical efficiency and engineering improvements in this technology in an effort to supply large radiance-conditioned laser diode array sources for its own internal programs. This effort has centered on the development of a modular integrated laser diode packaging technology with the goal of enabling the simple and flexible construction of high average power, high density, two-dimensional arrays with integrated cylindrical microlenses. Within LLNL, the principal applications of microlens-conditioned laser diode arrays are as high intensity pump sources for diode pumped solid state lasers (DPSSLs). A simple end-pumping architecture has been developed and demonstrated that allows the radiation from microlens-conditioned, two-dimensional diode array apertures to be efficiently delivered to the end of rod lasers. To date, pump powers as high as 2.5 kW have been delivered to 3 mm diameter laser rods. Such high power levels are critical for pumping solid state lasers in which the terminal laser level is a Stark level lying in the ground state manifold. Previously, such systems have often required operation of the solid state gain medium at low temperature to freeze out the terminal laser Stark level population. The authors recently developed high intensity pump sources overcome this difficulty by effectively pumping to much higher inversion levels, allowing efficient operation at or near room temperature. Because the end-pumping technology is scalable in absolute power, the number of rare-earth ions and transitions that can be effectively accessed for use in practical DPSSL systems has grown tremendously.
Ultraviolet light-emitting diode of a cubic boron nitride pn junction made at high pressure
Mishima, O.; Era, K.; Tanaka, J.; Yamaoka, S.
Injection luminescence in the ultraviolet is observed from a cubic boron nitride pn junction diode made at high pressure. Microscopic observation and spectroscopic studies show that the light emission occurs near the junction region only in the forward-bias condition. The spectra extend from approx.215 nm to the red, having a few peaks mainly in the ultraviolet.
Reliability of High Power Laser Diode Arrays Operating in Long Pulse Mode
NASA Technical Reports Server (NTRS)
Amzajerdian, Farzin; Meadows, Byron L.; Barnes, Bruce W.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.; Baker, Nathaniel R.
Reliability and lifetime of quasi-CW laser diode arrays are greatly influenced by their thermal characteristics. This paper examines the thermal properties of laser diode arrays operating in long pulse duration regime.
Method and system for homogenizing diode laser pump arrays
Bayramian, Andy J
An optical amplifier system includes a diode pump array including a plurality of semiconductor diode laser bars disposed in an array configuration and characterized by a periodic distance between adjacent semiconductor diode laser bars. The periodic distance is measured in a first direction perpendicular to each of the plurality of semiconductor diode laser bars. The diode pump array provides a pump output propagating along an optical path and characterized by a first intensity profile measured as a function of the first direction and having a variation greater than 10%. The optical amplifier system also includes a diffractive optic disposed along the optical path. The diffractive optic includes a photo-thermo-refractive glass member. The optical amplifier system further includes an amplifier slab having an input face and position along the optical path and separated from the diffractive optic by a predetermined distance. A second intensity profile measured at the input face of the amplifier slab as a function of the first direction has a variation less than 10%.
Efficient photochemical generation of peroxycarboxylic nitric anhydrides with ultraviolet light emitting diodes
NASA Astrophysics Data System (ADS)
Rider, N. D.; Taha, Y. M.; Odame-Ankrah, C. A.; Huo, J. A.; Tokarek, T. W.; Cairns, E.; Moussa, S. G.; Liggio, J.; Osthoff, H. D.
Photochemical sources of peroxycarboxylic nitric anhydrides (PANs) are utilized in many atmospheric measurement techniques for calibration or to deliver an internal standard. Conventionally, such sources rely on phosphor-coated low-pressure mercury (Hg) lamps to generate the UV light necessary to photo-dissociate a dialkyl ketone (usually acetone) in the presence of a calibrated amount of nitric oxide (NO) and oxygen (O2). In this manuscript, a photochemical PAN source in which the Hg lamp has been replaced by arrays of ultraviolet light-emitting diodes (UV-LEDs) is described. The output of the UV-LED source was analyzed by gas chromatography (PAN-GC) and thermal dissociation cavity ring-down spectroscopy (TD-CRDS). Using acetone, diethyl ketone (DIEK), diisopropyl ketone (DIPK), or di-n-propyl ketone (DNPK), respectively, the source produces peroxyacetic (PAN), peroxypropionic (PPN), peroxyisobutanoic (PiBN), or peroxy-n-butanoic nitric anhydride (PnBN) from NO in high yield (> 90%). Box model simulations with a subset of the Master Chemical Mechanism (MCM) were carried out to rationalize products yields and to identify side products. The use of UV-LED arrays offers many advantages over conventional Hg lamp setups, including greater light output over a narrower wavelength range, lower power consumption, and minimal generation of heat.
Chirped microlens arrays for diode laser circularization and beam expansion
NASA Astrophysics Data System (ADS)
Schreiber, Peter; Dannberg, Peter; Hoefer, Bernd; Beckert, Erik
Single-mode diode lasers are well-established light sources for a huge number of applications but suffer from astigmatism, beam ellipticity and large manufacturing tolerances of beam parameters. To compensate for these shortcomings, various approaches like anamorphic prism pairs and cylindrical telescopes for circularization as well as variable beam expanders based on zoomed telescopes for precise adjustment of output beam parameters have been employed in the past. The presented new approach for both beam circularization and expansion is based on the use of microlens arrays with chirped focal length: Selection of lenslets of crossed cylindrical microlens arrays as part of an anamorphic telescope enables circularization, astigmatism correction and divergence tolerance compensation of diode lasers simultaneously. Another promising application of chirped spherical lens array telescopes is stepwise variable beam expansion for circular laser beams of fiber or solid-state lasers. In this article we describe design and manufacturing of beam shaping systems with chirped microlens arrays fabricated by polymer-on-glass replication of reflow lenses. A miniaturized diode laser module with beam circularization and astigmatism correction assembled on a structured ceramics motherboard and a modulated RGB laser-source for photofinishing applications equipped with both cylindrical and spherical chirped lens arrays demonstrate the feasibility of the proposed system design approach.
Photodiode arrays having minimized cross-talk between diodes
Guckel, Henry (Madison, WI); McNamara, Shamus P. (Madison, WI)
Photodiode arrays are formed with close diode-to-diode spacing and minimized cross-talk between diodes in the array by isolating the diodes from one another with trenches that are formed between the photodiodes in the array. The photodiodes are formed of spaced regions in a base layer, each spaced region having an impurity type opposite to that of the base layer to define a p-n junction between the spaced regions and the base layer. The base layer meets a substrate at a boundary, with the substrate being much more heavily doped than the base layer with the same impurity type. The trenches extend through the base layer and preferably into the substrate. Minority carriers generated by absorption of light photons in the base layer can only migrate to an adjacent photodiode through the substrate. The lifetime and the corresponding diffusion length of the minority carriers in the substrate is very short so that all minority carriers recombine in the substrate before reaching an adjacent photodiode.
Study of phase-locked diode laser array and DFB/DBR surface emitting laser diode
NASA Astrophysics Data System (ADS)
Hsin, Wei
New types of phased-array and surface-emitting lasers are designed. The importance and approaches (or structures) of different phased array and surface emitting laser diodes are reviewed. The following are described: (1) a large optical cavity channel substrate planar laser array with layer thickness chirping; (2) a vertical cavity surface emitter with distributed feedback (DFB) optical cavity and a transverse junction buried heterostructure; (3) a microcavity distributed Bragg reflector (DBR) surface emitter; and (4) two surface emitting laser structures which utilized lateral current injection schemes to overcome the problems occurring in the vertical injection scheme.
Coherently Combined Diode Laser Arrays and Stacks
Hostetler, John L.
We have coherently combined up to 7.2 W CW using an individually addressable 10-element-array of 960-nm slab-coupled optical waveguide lasers (SCOWLs). We are currently scaling the phase-locked output power to 100 W using ...
Advances in high-power diode-pumped ultraviolet lasers
Acle V. Hicks; Charles X. Wang; Gary Y. Wang
In the past five years diode-pumped Q-switched vanadate and YAG lasers with 355 nm and 266 nm output have advanced in power level and reliability and are now qualified in many industrial processes. In this paper we will discuss the design and performance of these lasers with consideration of available power and wavelength of laser diodes, selection of materials for
Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes
Tim Kolbe; Arne Knauer; Chris Chua; Zhihong Yang; Sven Einfeldt; Patrick Vogt; Noble M. Johnson; Markus Weyers; Michael Kneissl
The polarization of the in-plane electroluminescence of (0001) orientated (In)(Al)GaN multiple quantum well light emitting diodes in the ultraviolet-A and ultraviolet-B spectral range has been investigated. The intensity for transverse-electric polarized light relative to the transverse-magnetic polarized light decreases with decreasing emission wavelength. This effect is attributed to rearrangement of the valence bands at the Gamma-point of the Brillouin zone
Nd:YAG laser side pumped by diode laser arrays
NASA Astrophysics Data System (ADS)
Tan, Hua; Huang, Weiling; Zhou, Zhouyou; Wang, Hailin; Cao, Hongbing; Wang, Ying
The major limitation of flashlamp-pumped solid-state lasers is the low overall efficiency. Replacing flashlamps with high power laser diodes allows an increase of system efficiency by over an order of magnitude. Because of the thermally induced stress fracture of the laser materials, power-scaling possibilities of end-pumped configurations are limited. Therefore side pump geometry has to be used for high power laser. The theory and the design of high power diode side-pumped Nd:YAG laser system is described. The Nd:YAG rod is side-pumped by diode laser arrays with wavelength at 808 nm. We analyze the result of our experiments and make some conclusions about the design of side-pumped laser.
Preliminary demonstration of power beaming with non-coherent laser diode arrays
Jordin T. Kare; Fred Mitlitsky; Andrew Weisberg
A preliminary demonstration of free-space electric power transmission has been conducted using non-coherent laser diode arrays as the transmitter and standard silicon photovoltaic cell arrays as the receiver. The transmitter assembly used a high-power-density array of infrared laser diode bars, water cooled via integrated microchannel heat sinks and focused by cylindrical microlenses. The diode array composite beam was refocused by
Stripe-array diode-laser in an off-axis external cavity: Theory and experiment
Vladimirov, Andrei G.
Stripe-array diode-laser in an off-axis external cavity: Theory and experiment Andreas Jechow1, Mohrenstr. 39, 10117 Berlin email@example.com, firstname.lastname@example.com Abstract: Stripe-array diode of America OCIS codes: (000.4430) General: Numerical approximation and analysis; (140.2020) Diode lasers
Narrowing of high power diode laser arrays using reflection feedback from an etalon
Romalis, Mike
Narrowing of high power diode laser arrays using reflection feedback from an etalon M. V. Romalisa of Physics. S0003-6951 00 03434-3 High power 20Ł100 W diode laser arrays are com- monly used for production of spin-polarized noble gases.1 The diode lasers are used for optical pumping of Rb or K atoms, which
Gamma radiation exposure of MCT diode arrays
F. F. Sizov; I. O. Lysiuk; J. V. Gumenjuk-Sichevska; S. G. Bunchuk; V. V. Zabudsky
Investigations of electrical properties of long-wavelength infrared (LWIR) mercury cadmium telluride arrays exposed to gamma-radiation have been performed. Resistance-area product characteristics of LWIR n+-p-photodiodes have been investigated using a microprobe technique at T ap 78 K before and after exposure to various doses of gamma-radiation (Co60 Gammas). The current transport mechanisms for those structures are described within the framework of
Flow-velocity measurements with a laser diode array.
Azzazy, M; Potts, R L; Zhou, L; Rosow, B
To measure flow velocity, a new technique, laser diode array velocimetry, generates multiple laser spots (four or more) separated by short distances (20-100 mum) at the probe volume. Particles that pass through the probe volume generate a signal that is analyzed by a digital signal processor for frequency content. The product of frequency and laser-to-laser spot separation determines the velocity. Rotating wire and wind-tunnel experiments confirm the performance of the new technique. An error analysis showed that the uncertainties in the processed diode array velocimetry signal frequency were less than 0.3%, and uncertainties in the beam-to-beam separation were less than +/-0.05%. PMID:18253264
Diode laser arrays for dynamic infrared scene projection
D. Brett Beasley; John B. Cooper
A novel concept for dynamic IR scene projection using IR diode lasers has been developed. This technology offers significant cost and performance advantages over other currently available projector technologies. Performance advantages include high dynamic range, multiple wavebands, and high frame rates. A projector system which utilizes a 16-element linear array has been developed and integrated into the millimeter wave\\/infrared (MMW\\/IR)
Application of ultraviolet light-emitting diode photocatalysis to remove volatile organic compounds from indoor air
Rifath Sharmin; Madhumita B. Ray
Photocatalytic oxidation (PCO) is a promising technology for indoor air purification due to low operating cost, potentially long service life, and low maintenance. Ultraviolet light-emitting diode (UVLED) is a new concept in the field of PCO, which has several advantages over conventional UV light sources. Limited research has been conducted using UVLED PCO for air treatment. This study demonstrated the
Application of Ultraviolet Light Emitting Diode Photocatalysis to Remove VOCs from Indoor Air
Rifath Sharmin; Madhumita B. Ray
Photocatalytic oxidation (PCO) is a promising technology for indoor air purification due to low operating cost, potentially long service life, and low maintenance. Ultraviolet light emitting diode (UVLED) is a new concept in the field of PCO, which has several advantages over conventional UV light sources. Limited research has been conducted using UVLED PCO for air treatment. This study demonstrated
Photon counting photodiode array detector for far ultraviolet (FUV) astronomy
NASA Technical Reports Server (NTRS)
Hartig, G. F.; Moos, H. W.; Pembroke, R.; Bowers, C.
A compact, stable, single-stage intensified photodiode array detector designed for photon-counting, far ultraviolet astronomy applications employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain pulses with a narrowly peaked pulse height distribution. The P-20 output phosphor exhibits a very short decay time, due to the high current density of the electron pulses. This intensifier is being coupled to a self-scanning linear photodiode array which has a fiber optic input window which allows direct, rigid mechanical coupling with minimal light loss. The array was scanned at a 250 KHz pixel rate. The detector exhibits more than adequate signal-to-noise ratio for pulse counting and event location. Previously announced in STAR as N82-19118
Linear laser diode arrays for improvement in optical disk recording
NASA Technical Reports Server (NTRS)
Alphonse, G. A.; Carlin, D. B.; Connolly, J. C.
The development of individually addressable laser diode arrays for multitrack magneto-optic recorders for space stations is discussed. Three multi-element channeled substrate planar (CSP) arrays with output power greater than 30 mW with linear light vs current characteristics and stable single mode spectra were delivered to NASA. These devices have been used to demonstrate for the first time the simultaneous recording of eight data tracks on a 14-inch magneto-optic erasable disk. The yield of these devices is low, mainly due to non-uniformities inherent to the LPE growth that was used to fabricate them. The authors have recently developed the inverted CSP, based on the much more uniform MOCVD growth techniques, and have made low threshold quantum well arrays requiring about three times less current than the CSP to deliver 30 mW CW in a single spatial mode. The inverted CSP is very promising for use in space flight recorder applications.
Deep diode arrays for X-ray detection
NASA Technical Reports Server (NTRS)
Zemel, J. N.
Temperature gradient zone melting process was used to form p-n junctions in bulk of high purity silicon wafers. These diodes were patterned to form arrays for X-ray spectrometers. The whole fabrication processes for these X-ray detectors are reviewed in detail. The p-n junctions were evaluated by (1) the dark diode I-V measurements, (2) the diode C sub I - V measurements, and (3) the MOS C-V measurements. The results showed that these junctions were linearly graded in charge distribution with low reverse bias leakage current flowing through them (few nA at -10 volts). The X-ray detection experiments showed that an FWHM of 500 eV was obtained from these diodes with a small bias of just -5 volts (for X-ray source Fe55). A theoretical model was proposed to explain the extra peaks found in the energy spectra and a very interesting point - cross talk effect was pointed out. This might be a solution to the problem of making really high resolution X-ray spectrometers.
Bandwidth narrowing of a diode laser array by beam injection using photorefractive double phase conjugation
Andreas Hermerschmidt; F. Wang; Peter Pogany; Hans J. Eichler
A diode laser array consisting of three initially uncoupled stripes is injection-locked by a 50 mW single-mode frequency tunable diode laser. Phase-conjugation is achieved by pumping a photorefractive crystal by the beams emitted from the master oscillator and the slave laser array. The injected beam is phase-conjugated with respect to the beam emitted by the slave diode laser array. The
Vacuum Nanohole Array Embedded Phosphorescent Organic Light Emitting Diodes
Jeon, Sohee; Lee, Jeong-Hwan; Jeong, Jun-Ho; Song, Young Seok; Moon, Chang-Ki; Kim, Jang-Joo; Youn, Jae Ryoun
Light extraction from organic light-emitting diodes that utilize phosphorescent materials has an internal efficiency of 100% but is limited by an external quantum efficiency (EQE) of 30%. In this study, extremely high-efficiency organic light emitting diodes (OLEDs) with an EQE of greater than 50% and low roll-off were produced by inserting a vacuum nanohole array (VNHA) into phosphorescent OLEDs (PhOLEDs). The resultant extraction enhancement was quantified in terms of EQE by comparing experimentally measured results with those produced from optical modeling analysis, which assumes the near-perfect electric characteristics of the device. A comparison of the experimental data and optical modeling results indicated that the VNHA extracts the entire waveguide loss into the air. The EQE obtained in this study is the highest value obtained to date for bottom-emitting OLEDs. PMID:25732061
Photoluminescence performance enhancement of ZnO/MgO heterostructured nanowires and their applications in ultraviolet laser diodes.
Shi, Zhi-Feng; Zhang, Yuan-Tao; Cui, Xi-Jun; Zhuang, Shi-Wei; Wu, Bin; Chu, Xian-Wei; Dong, Xin; Zhang, Bao-Lin; Du, Guo-Tong
Vertically aligned ZnO/MgO coaxial nanowire (NW) arrays were prepared on sapphire substrates by metal-organic chemical vapor deposition combined with a sputtering system. We present a comparative investigation of the morphological and optical properties of the produced heterostructures with different MgO layer thicknesses. Photoluminescence measurements showed that the optical performances of ZnO/MgO coaxial NWs were strongly dependent on the MgO layer thickness. The intensity of deep-level emission (DLE) decreased monotonously with the increase of MgO thickness, while the enhancement of ultraviolet (UV) emission showed a critical thickness of 15 nm, achieving a maximum intensity ratio (?226) of IUV/IDLE at the same time. The significantly improved exciton emission efficiency of the coaxial NW structures allows us to study the surface passivation effect, photogenerated carrier confinement and transfer in terms of energy band theory. More importantly, we achieved an ultralow threshold (4.5 mA, 0.58 A cm(-2)) electrically driven UV lasing action based on the ZnO/MgO NW structures by constructing an Au/MgO/ZnO metal/insulator/semiconductor diode, and the continuous-current-driven diode shows a good temperature tolerance. The results obtained on the unique optical properties of ZnO/MgO coaxial NWs shed light on the design and development of ZnO-based UV laser diodes assembled with nanoscale building blocks. PMID:25803480
Ultraviolet photodetectors and imaging arrays based on III-V nitride heterostructures
NASA Astrophysics Data System (ADS)
Brown, Jeffrey David
The III-V nitride class of compound semiconductors has received much attention in the last decade. These materials have a wide, direct bandgap, making them a prime candidate for optoelectronic devices in the blue, green, and ultraviolet spectral regions. These materials exhibit impressive optical, electrical, and thermal properties, even though there are fundamental materials issues that are thus far unresolved. This work explores the application of III-V nitride semiconductors to optical detectors in the ultraviolet region of the electromagnetic spectrum. Metalorganic vapor phase epitaxy was used to synthesize thin film p-i-n photodiode structures on double side polished sapphire substrates; these films were characterized for optical, electrical and structural properties. The grown structures were designed to respond to a predetermined region of the UV spectrum when illuminated from the substrate side. These structures were fabricated into devices using generally accepted techniques for dry etching and p and n-contact metallizations. Test devices were characterized using tools developed by the author. These devices demonstrated as high as 80% quantum efficiency and extremely low dark currents; resulting in spectral detectivities as large as 6 * 1013 cmHz1/2W-1. Devices were designed and demonstrated for a series of detection regions ranging from 365 nm to 250 nm. Photolithography masks were designed to allow the fabrication of photodiode arrays that would hybridize to commercially available CMOS based readout integrated circuits (ROICs), used routinely for infrared photodiode imaging. Photodiode arrays were fabricated and indium bumps were deposited onto the diode contacts and the ROICs to provide electrical connection. The hybrid detector arrays were placed in leadless chip carriers, wirebonded, and connected to commercially available drive and readout circuitry. Images of UV scenes were focused onto the arrays using fused quartz lenses. These images and movies were successfully collected at frame rates up to 240 Hz using both 32 x 32 and 128 x 128 III-V nitride based UV photodiode imagers.
Animation of Diode Array Detection in High Performance Liquid Chromatography
NSDL National Science Digital Library
This animation site deals specifically with diode array detection for liquid chromatography. The animations are short (one to two minutes) and can easily be shown in class as part of a lecture. They are extremely helpful in illustrating key components and concepts of chromatographic systems. Users are encouraged to explore the site and the other brief animations as well. Separate links to other simulations by the same company (TRSL) are also listed on ASDL. This site requires FLASH version 7 or higher in order to work properly.
Protection circuitry for high-power diode laser arrays
NASA Astrophysics Data System (ADS)
Saam, Brian T.; Conradi, Mark S.
A comprehensive protection scheme is presented for use with high-power (ś500 W dc input) diode laser arrays. The circuitry requires no separate power, using instead the voltage from the laser's power supply. Overcurrent and overvoltage silicon controlled rectifier crowbars are the primary protection circuits. In addition, tripping of either crowbar will turn off the main power to the laser's power supply. This feature makes use of a main power controller that incorporates two interlock loops, for protection against overtemperature, low coolant flow, undervoltage, and other undesirable conditions.
Narrow-bandwidth diode-laser-based blue and ultraviolet light source
Ch. Schwedes; E. Peik; J. von Zanthier; A. Y. Nevsky; H. Walther
. ĀĀA compact, tunable and narrow-bandwidth laser source for blue and ultraviolet radiation is presented. A grating-stabilized\\u000a diode laser at 922Ānm is frequency-stabilized to below 100ĀHz relative to a reference resonator. Injection of the diode-laser\\u000a light into a tapered amplifier yields a power of 0.5ĀW. In a first frequency-doubling stage, more than 200ĀmW of blue light\\u000a at 461Ānm is generated
Passive intrinsic-linewidth narrowing of ultraviolet extended-cavity diode laser by weak optical feedback
Samutpraphoot, Polnop; Lin, Qian; Gangloff, Dorian; Bylinskii, Alexei; Braverman, Boris; Kawasaki, Akio; Raab, Christoph; Kaenders, Wilhelm; Vuleti?, Vladan
We present a simple method for narrowing the intrinsic Lorentzian linewidth of a commercial ultraviolet grating extended-cavity diode laser (TOPTICA DL Pro) using weak optical feedback from a long external cavity. We achieve a suppression in frequency noise spectral density of 20 dB measured at frequencies around 1 MHz, corresponding to the narrowing of the intrinsic Lorentzian linewidth from 200 kHz to 2 kHz. The system is suitable for experiments requiring a tunable ultraviolet laser with narrow linewidth and low high-frequency noise, such as precision spectroscopy, optical clocks, and quantum information science experiments.
Fiber optic coupling of a microlens conditioned, stacked semiconductor laser diode array
R. J. Beach; W. J. Benett; S. T. Mills
The output radiation from the two-dimensional aperture of a semiconductor laser diode array is efficiently coupled into an optical fiber. The two-dimensional aperture is formed by stacking individual laser diode bars on top of another in a ``rack and stack`` configuration. Coupling into the fiber is then accomplished using individual microlenses to condition the output radiation of the laser diode
V-shaped resonators for addition of broad-area laser diode arrays
Liu, Bo; Liu, Yun; Braiman, Yehuda Y.
A system and method for addition of broad-area semiconductor laser diode arrays are described. The system can include an array of laser diodes, a V-shaped external cavity, and grating systems to provide feedback for phase-locking of the laser diode array. A V-shaped mirror used to couple the laser diode emissions along two optical paths can be a V-shaped prism mirror, a V-shaped stepped mirror or include multiple V-shaped micro-mirrors. The V-shaped external cavity can be a ring cavity. The system can include an external injection laser to further improve coherence and phase-locking.
Ultraviolet light emitting diodes and hydrogen peroxide in the photodegradation of aqueous phenol
Sari H. Vilhunen; Mika E. T. Sillanpõõ
The novel system of ultraviolet (UV) light emitting diodes (LED) and hydrogen peroxide (H2O2) was studied for the degradation of phenol as a model organic pollutant in water. The effect of different viewing angles (15 and 120░), wavelengths (255, 265 and 280nm) and phenol and H2O2 concentrations were investigated in four photolytic batch reactors. Phenol degradation was observed to be
Characterization of High-power Quasi-cw Laser Diode Arrays
NASA Technical Reports Server (NTRS)
Stephen, Mark A.; Vasilyev, Aleksey; Troupaki, Elisavet; Allan, Graham R.; Kashem, Nasir B.
NASA s requirements for high reliability, high performance satellite laser instruments have driven the investigation of many critical components; specifically, 808 nm laser diode array (LDA) pump devices. Performance and comprehensive characterization data of Quasi-CW, High-power, laser diode arrays is presented.
Space qualification and environmental testing of quasicontinuous wave laser diode arrays
Elisavet Troupaki; Aleksey A. Vasilyev; Nasir B. Kashem; Graham R. Allan; Mark A. Stephen
NASAÆs mission requirements for spaceborne laser diode arrays lead to a set of tests peculiar to space flight. The goal of these tests is to determine if vibration, radiation, or vacuum will impair the operation or lifetime of nominally 100 W quasicontinuous wave 808 nm laser diode arrays. To simulate the stresses expected during a mission, terrestrial tests involve mechanical
Space qualification and environmental testing of quasicontinuous wave laser diode arrays
Elisavet Troupaki; Aleksey A. Vasilyev; Nasir B. Kashem; Graham R. Allan; Mark A. Stephen
NASA's mission requirements for spaceborne laser diode arrays lead to a set of tests peculiar to space flight. The goal of these tests is to determine if vibration, radiation, or vacuum will impair the operation or lifetime of nominally 100 W quasicontinuous wave 808 nm laser diode arrays. To simulate the stresses expected during a mission, terrestrial tests involve mechanical
High-density pulsed laser diode arrays for SSL pumping
NASA Astrophysics Data System (ADS)
Feeler, Ryan; Stephens, Edward
Northrop Grumman Cutting Edge Optronics has developed a new laser diode array package with minimal bar-to-bar spacing. These High Density Stack (HDS) packages allow for a power density increase on the order of ~ 2.5x when compared to industry-standard arrays. This work contains an overview of the manufacturing process, as well as representative data for 5-, 10-, and 20-bar arrays. Near-field and power vs. current data is presented in each case. Power densities approaching 15 kW/cm2 are presented. In addition, power and wavelength are presented as a function of pulse width in order to determine the acceptable operational parameters for this type of array. In the low repetition rate Nd:YAG pumping regime, all devices are shown to operate with relatively low junction temperatures. A discussion of future work is also presented, with a focus on extending the HDS architecture to reliable operation at 300W per bar. This will enable power densities of approximately 25 kW/cm2.
Improving Reliability of High Power Quasi-CW Laser Diode Arrays for Pumping Solid State Lasers
NASA Technical Reports Server (NTRS)
Amzajerdian, Farzin; Meadows, Byron L.; Baker, Nathaniel R.; Barnes, Bruce W.; Baggott, Renee S.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.
Most Lidar applications rely on moderate to high power solid state lasers to generate the required transmitted pulses. However, the reliability of solid state lasers, which can operate autonomously over long periods, is constrained by their laser diode pump arrays. Thermal cycling of the active regions is considered the primary reason for rapid degradation of the quasi-CW high power laser diode arrays, and the excessive temperature rise is the leading suspect in premature failure. The thermal issues of laser diode arrays are even more drastic for 2-micron solid state lasers which require considerably longer pump pulses compared to the more commonly used pump arrays for 1-micron lasers. This paper describes several advanced packaging techniques being employed for more efficient heat removal from the active regions of the laser diode bars. Experimental results for several high power laser diode array devices will be reported and their performance when operated at long pulsewidths of about 1msec will be described.
Injection locking of a high power ultraviolet laser diode for laser cooling of ytterbium atoms
Toshiyuki Hosoya; Martin Miranda; Ryotaro Inoue; Mikio Kozuma
We developed a high-power laser system at a wavelength of 399 nm for laser cooling of ytterbium atoms with ultraviolet laser diodes. The system is composed of an external cavity laser diode providing frequency stabilized output at a power of 40 mW and another laser diode for amplifying the laser power up to 220 mW by injection locking. The systematic method for optimization of our injection locking can also be applied to high power light sources at any other wavelengths. Our system, which does not depend on complex nonlinear frequency-doubling, has great importance for implementing transportable optical lattice clocks, and is also useful for investigations on condensed matter physics or quantum information processing using cold atoms.
Mid-ultraviolet light-emitting diode detects dipicolinic acid.
Bogart, Katherine Huderle Andersen; Lee, Stephen Roger; Temkin, Henryk (Texas Tech University, Lubbock, TX); Crawford, Mary Hagerott; Dasgupta, Purnendu K. (Texas Tech University, Lubbock, TX); Li, Qingyang (Texas Tech University, Lubbock, TX); Allerman, Andrew Alan; Fischer, Arthur Joseph
Dipicolinic acid (DPA, 2,6-pyridinedicarboxylic acid) is a substance uniquely present in bacterial spores such as that from anthrax (B. anthracis). It is known that DPA can be detected by the long-lived fluorescence of its terbium chelate; the best limit of detection (LOD) reported thus far using a large benchtop gated fluorescence instrument using a pulsed Xe lamp is 2 nM. We use a novel AlGaN light-emitting diode (LED) fabricated on a sapphire substrate that has peak emission at 291 nm. Although the overlap of the emission band of this LED with the absorption band of Tb-DPA ({lambda}{sub max} doublet: 273, 279 nm) is not ideal, we demonstrate that a compact detector based on this LED and an off-the-shelf gated photodetection module can provide an LOD of 0.4 nM, thus providing a basis for convenient early warning detectors.
Thin planar package for cooling an array of edge-emitting laser diodes
Mundinger, David C. (Stockton, CA); Benett, William J. (Livermore, CA)
A laser diode array is disclosed that includes a plurality of planar assemblies and active cooling of each assembly. The laser diode array may be operated in a long duty cycle, or in continuous operation. A laser diode bar and a microchannel heat sink are thermally coupled in a compact, thin planar assembly having the laser diode bar located proximate to one edge. In an array, a number of such thin planar assemblies are secured together in a stacked configuration, in close proximity so that the laser diodes are spaced closely. The cooling means includes a microchannel heat sink proximate to the laser diode bar to absorb heat generated by laser operation. To provide the coolant to the microchannels, each thin planar assembly comprises passageways that connect the microchannels to inlet and outlet corridors. Each inlet passageway may comprise a narrow slot that directs coolant into the microchannels and increases the velocity of flow therethrough. The corridors comprises holes extending through each of the assemblies in the array. The inlet and outlet corridors are connected to a conventional coolant circulation system. The laser diode array with active cooling has applications as an optical pump for high power solid state lasers, or by mating the diodes with fiber optic lenses. Further, the arrays can be useful in applications having space constraints and energy limitations, and in military and space applications. The arrays can be incorporated in equipment such as communications devices and active sensors.
Operation of a single mode external-cavity laser diode array near 780 nm S. B. Bayrama)
Bayram, S. Burńin
; accepted 14 August 2002 We have narrowed the spectral bandwidth of a commercial 2 W laser diode arrayOperation of a single mode external-cavity laser diode array near 780 nm S. B. Bayrama) and T. E to be less than 120 MHz near 780 nm. The external-cavity laser diode array system is a standard double
High-performance silicon single-photon avalanche diode array
NASA Astrophysics Data System (ADS)
Rech, Ivan; Gulinatti, Angelo; Zappa, Franco; Ghioni, Massimo; Cova, Sergio
Over the past few years there has been a growing interest in monolithic arrays of single photon avalanche diodes (SPAD) for spatially resolved detection of faint ultrafast optical signals. SPADs implemented in CMOS-compatible planar technologies offer the typical advantages of microelectronic devices (small size, ruggedness, low voltage, low power, etc.). Furthermore, they have inherently higher photon detection efficiency than PMTs and are able to provide, beside sensitivities down to single-photons, very high acquisition speeds (i.e. either high frame-rates or very short integration time-slots). SPADs offer several advantages over other commercially available imagers. For example, CCDs and similar imagers lack in speed because their readout process is based on a slow charge-transfer mechanisms. CMOS APS, on the other hand, are unable to detect very faint optical signals, due to poor sensitivity and noisy electronics. In order to make SPAD array more and more competitive it is necessary to face several issues: dark counts, quantum efficiency, crosstalk, timing performance. These issues will be discussed in the context of two possible approaches to such a challenge: employing a standard industrial CMOS technology or developing a dedicated technology. Advances recently attained will be outlined with reference to both photon counting and Time correlated single photon counting detector arrays.
Electroluminescence spectra of ultraviolet light-emitting diodes based on p-n-heterostructures coated with phosphors
Gal'china, N. A.; Kogan, L. M. [Scientific and Production Center of Optoelectronic Devices OPTEL (Russian Federation); Soshchin, N. P. [Federal State Unitary Enterprise NII Platan (Russian Federation); Shirokov, S. S.; Yunovich, A. E. [Moscow State University, Physics Faculty (Russian Federation)], E-mail: firstname.lastname@example.com
The electroluminescence spectra of light-emitting diodes based on p-n heterostructures of the InGaN/AlGaN/GaN type are studied in the near-ultraviolet spectral region (360-405 nm). The spectra are peaked at the wavelengths 385 and 395 nm, and the intensity of emission falls exponentially with the photon energy in the shorter-wavelength and longer-wavelength regions. The emitters in the green and yellow spectral regions based on these light-emitting diodes coated with silicate phosphors are studied. The luminescence spectra of phosphors have the Gaussian shape and maximums in the range from 525 to 560 nm. The color characteristics of emitters depend on the ratios of intensities of the ultraviolet and yellow-green bands. The possibilities of fabrication of light-emitting diodes of visible luminescence based on ultraviolet light-emitting diodes that excite colored phosphors are discussed.
Frequency-narrowed external-cavity diode-laser-array bar
B. Chann; I. Nelson; T. G. Walker
We demonstrate that appropriately designed external cavities can be used to frequency narrow high-power diode-array bars. Using a commercial 20-W array, we narrow the linewidth to 50 GHz with 14 W of cw output power. A magnifying telescope and a cylindrical collimating lens minimize broadening owing to curvature in the alignment of the diode-array elements. ® 2000 Optical Society of
Facile fabrication of a ultraviolet tunable MoS2/p-Si junction diode
NASA Astrophysics Data System (ADS)
Serrano, William; Pinto, Nicholas J.; Naylor, Carl H.; Kybert, Nicholas J.; Johnson, A. T. Charlie
Chemical vapor deposition grown MoS2 single crystals were transferred onto the edge of a p-Si/SiO2 wafer, forming an abrupt heterogeneous junction diode at the MoS2/p-Si interface. When electrically characterized as a field effect transistor, MoS2 exhibits an n-type response and can be doped in the presence of ultraviolet (UV) light. As a diode, it operates satisfactorily in air, but has higher currents in vacuum with a turn on voltage of ś1.3 V and an on/off ratio of 20 at ▒2 V. UV irradiation increases the diode on state current, decreases the turn-on voltage, and reduces the ideality parameter below 2. These changes are reversible after annealing in air as desorption of electron trapping species like O2- and H2O- are believed responsible for this effect. A circuit integrating this diode was used to rectify a 1 kHz signal with an efficiency of 12%. Its simple design, coupled with the ability to clip AC signals, sense UV light, and reversibly tune these diodes, makes them inexpensive, multifunctional, and usable as active or passive circuit components in complex electronics.
Single Photon Avalanche Diodes: Towards the Large Bidimensional Arrays
Privitera, Simona; Tudisco, Salvatore; Lanzan", Luca; Musumeci, Francesco; Pluchino, Alessandro; Scordino, Agata; Campisi, Angelo; Cosentino, Luigi; Finocchiaro, Paolo; Condorelli, Giovanni; Mazzillo, Massimo; Lombardo, Salvo; Sciacca, Emilio
Single photon detection is one of the most challenging goals of photonics. In recent years, the study of ultra-fast and/or low-intensity phenomena has received renewed attention from the academic and industrial communities. Intense research activity has been focused on bio-imaging applications, bio-luminescence, bio-scattering methods, and, more in general, on several applications requiring high speed operation and high timing resolution. In this paper we present design and characterization of bi-dimensional arrays of a next generation of single photon avalanche diodes (SPADs). Single photon sensitivity, dark noise, afterpulsing and timing resolution of the single SPAD have been examined in several experimental conditions. Moreover, the effects arising from their integration and the readout mode have also been deeply investigated.
Linewidth-tunable laser diode array for rubidium laser pumping
Li Zhiyong; Tan Rongqing; Xu Cheng; Li Lin
To optimise the pump source for a high-power diodepumped rubidium vapour laser, we have designed a laser diode array (LDA) with a narrowed and tunable linewidth and an external cavity formed by two volume Bragg gratings (VBGs). Through controlling the temperature differences between the two VBGs, the LDA linewidth, which was 1.8 nm before mounting the two VBGs, was tunable from 100 pm to 0.2 nm, while the output power changed by no more than 4 %. By changing simultaneously the temperature in both VBGs, the centre wavelength in air of the linewidth-tunable LDA was tunable from 779.40 nm to 780.05 nm. (control of laser radiation parameters)
Environmental testing of a diode-laser-pumped Nd:YAG laser and a set of diode-laser-arrays
NASA Astrophysics Data System (ADS)
Hemmati, H.; Lesh, J. R.
Results of the environmental test of a compact, rigid and lightweight diode-laser-pumped Nd:YAG laser module are discussed. All optical elements are bonded onto the module using space applicable epoxy, and two 200 mW diode laser arrays for pump sources are used to achieve 126 mW of CW output with about 7 percent electrical-to-optical conversion efficiency. This laser assembly and a set of 20 semiconductor diode laser arrays were environmentally tested by being subjected to vibrational and thermal conditions similar to those experienced during launch of the Space Shuttle, and both performed well. Nevertheless, some damage to the laser front facet in diode lasers was observed. Significant degradation was observed only on lasers which performed poorly in the life test. Improvements in the reliability of the Nd:YAG laser are suggested.
Short range laser obstacle detector. [for surface vehicles using laser diode array
NASA Technical Reports Server (NTRS)
Kuriger, W. L. (inventor)
A short range obstacle detector for surface vehicles is described which utilizes an array of laser diodes. The diodes operate one at a time, with one diode for each adjacent azimuth sector. A vibrating mirror a short distance above the surface provides continuous scanning in elevation for all azimuth sectors. A diode laser is synchronized with the vibrating mirror to enable one diode laser to be fired, by pulses from a clock pulse source, a number of times during each elevation scan cycle. The time for a given pulse of light to be reflected from an obstacle and received is detected as a measure of range to the obstacle.
Monolithic Schottky-collector resonant tunnel diode oscillator arrays to 650 GHz
M. Reddy; S. C. Martin; A. C. Molnar; R. E. Muller; R. P. Smith; P. H. Siegel; M. J. Mondry; M. J. W. Rodwell; H. Kroemer
We report monolithic array oscillators incorporating Schottky-collector resonant tunnel diodes (SRTD's). In the SRTD, a 0.1-?m width Schottky collector contact provides a greatly reduced device series resistance, resulting in an estimated 2.2 THz maximum frequency of oscillation. A 64-element oscillator array oscillated at 650 GHz while a 16-element array produced 28 ?W at 290 GHz
IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 20, NO. 13, JULY 1, 2008 1085 Curved Waveguide Array Diode Lasers for
Coleman, James J.
these components. Combining individual elements of semiconductor laser diode arrays has been attempted using-brightness arrays [4], [5]. In this method, an array of narrow stripe semiconductor lasers is coupled togetherIEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 20, NO. 13, JULY 1, 2008 1085 Curved Waveguide Array Diode
Enhanced out-coupling efficiency of organic light-emitting diodes using an nanostructure imprinted by an alumina nanohole array
Endo, Kuniaki [Center for Organic Photonics and Electronics Research, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Yokohama Research Laboratories, Mitsubishi Rayon Co., Ltd., 10-1 Daikoku, Tsurumi, Yokohama 230-0053 (Japan); Adachi, Chihaya [Center for Organic Photonics and Electronics Research, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan)
We demonstrate organic light-emitting diodes (OLEDs) with enhanced out-coupling efficiency containing nanostructures imprinted by an alumina nanohole array template that can be applied to large-emitting-area and flexible devices using a roll-to-roll process. The nanostructures are imprinted on a glass substrate by an ultraviolet nanoimprint process using an alumina nanohole array mold and then an OLED is fabricated on the nanostructures. The enhancement of out-coupling efficiency is proportional to the root-mean-square roughness of the nanostructures, and a maximum improvement of external electroluminescence quantum efficiency of 17% is achieved. The electroluminescence spectra of the OLEDs indicate that this improvement is caused by enhancement of the out-coupling of surface plasmon polaritons.
Passive intrinsic-linewidth narrowing of ultraviolet extended-cavity diode laser by weak optical feedback.
Samutpraphoot, Polnop; Weber, Sophie; Lin, Qian; Gangloff, Dorian; Bylinskii, Alexei; Braverman, Boris; Kawasaki, Akio; Raab, Christoph; Kaenders, Wilhelm; Vuleti?, Vladan
We present a simple method for narrowing the intrinsic Lorentzian linewidth of a commercial ultraviolet grating extended-cavity diode laser (TOPTICA DL Pro) using weak optical feedback from a long external cavity. We achieve a suppression in frequency noise spectral density of 20 dB measured at frequencies around 1 MHz, corresponding to the narrowing of the intrinsic Lorentzian linewidth from 200 kHz to 2 kHz. Provided additional active low-frequency noise suppression and long-term drift compensation, the system is suitable for experiments requiring a tunable ultraviolet laser with narrow linewidth and low high-frequency noise, such as precision spectroscopy, optical clocks, and quantum information science experiments. PMID:24921280
Fiber-coupling technique for high-power diode laser arrays
Hans-Georg Treusch; Keming Du; Markus Baumann; Volker Sturm; Bodo Ehlers; Peter Loosen
Monolithic linear arrays of diode lasers, also known as diode laser bars, are the basic elements for most high-power laser applications such as solid-state laser pumping or material processing. Cylindrical microlenses used as fast- axis collimators for 10-mm diode bars require very high angles of aperture (up to 100 degree FW1\\/e2, equivalent to a numerical aperture of approx. 0.8) to
Fiber optic coupling of a microlens conditioned, stacked semiconductor laser diode array
Raymond J. Beach; William J. Benett; Steven T. Mills
The output radiation from the two-dimensional aperture of a semiconductor laser diode array is efficiently coupled into an optical fiber. The two-dimensional aperture is formed by stacking individual laser diode bars on top of another in a \\
Wavelength fluctuations in pulsed variable spacing phase-locked laser diode arrays
NASA Technical Reports Server (NTRS)
Fuhr, P. L.
Spectra taken for a pulsed variable spacing phase-locked laser diode array (VSA) were recorded and processed to determine the magnitude of wavelength fluctuations present in the diode's output field. Analysis revealed that a pulsed VSA emits primarily into a single longitudinal mode.
Thermal profile of high power laser diode arrays and implications in line-narrowing using external cavities
Thermal profile of high power laser diode arrays and implications in line-narrowing using external for current commercially available laser diode arrays. The linewidth can be narrowed using an external cavity cavity line narrowing is successfully used for single element laser diodes. However, current high power
Vacuum nano-hole array embedded organic light emitting diodes
NASA Astrophysics Data System (ADS)
Jeon, Sohee; Jeong, Jun-Ho; Song, Young Seok; Jeong, Won-Ik; Kim, Jang-Joo; Youn, Jae Ryoun
We demonstrated a nano-hole array (NHA) embedded structure that was fabricated for organic light emitting diodes (OLEDs) using a robust reverse transfer process. The NHA structure is proposed in this study as a strategy for maximizing the diffraction strength of two dimensional photonic crystals (PCs) by engineering vacuum nano-holes inside a dielectric slab. The electroluminescence (EL) intensity of the OLED was improved by more than twice. Such an optical enhancement was evaluated by using the angular dependence of photoluminescence (PL). The FDTD simulation was carried out to optimize the NHA structure for extraction of the emission induced from both vertical and horizontal dipoles. We explored the effect of the NHA structure on the extraction improvement converted from waveguide mode by measuring EL intensities of the devices with a hemisphere lens. In addition, the transfer process employed in this study yielded extremely low surface roughness, and thus outstanding electrical characteristics.We demonstrated a nano-hole array (NHA) embedded structure that was fabricated for organic light emitting diodes (OLEDs) using a robust reverse transfer process. The NHA structure is proposed in this study as a strategy for maximizing the diffraction strength of two dimensional photonic crystals (PCs) by engineering vacuum nano-holes inside a dielectric slab. The electroluminescence (EL) intensity of the OLED was improved by more than twice. Such an optical enhancement was evaluated by using the angular dependence of photoluminescence (PL). The FDTD simulation was carried out to optimize the NHA structure for extraction of the emission induced from both vertical and horizontal dipoles. We explored the effect of the NHA structure on the extraction improvement converted from waveguide mode by measuring EL intensities of the devices with a hemisphere lens. In addition, the transfer process employed in this study yielded extremely low surface roughness, and thus outstanding electrical characteristics. Electronic supplementary information (ESI) available: The contents include details about the FDTD modeling, PL specimen fabrication, OLED device fabrication, and PL/EL measurement set-up. Further information is provided relating to the NHA substrate as well. See DOI: 10.1039/c3nr05331h
Means for phase locking the outputs of a surface emitting laser diode array
Lesh, J.R.
An array of injection phase-locked diode lasers is described utilizing as a master a separate laser source, and means for coupling light from the master laser source into each diode laser of the array of diode lasers. The array is fabricated in a body of semi-conductor material. Each diode laser has a back facet on one side of the body of semiconductor material and a front facet on an opposite side of the body of semiconductor material. The light coupling means comprises a hologram prepared for producing from the output of the master laser source a set of distinct, spatially separated beams, each one directed into the back facet of each diode laser . To assure emission of phase coherent light from the array of diode lasers, the hologram is positioned between the master laser source and the one side of the body of semiconductor material. The hologram is prepared by illuminating a holographic emulsion plate with an image of the array of diode lasers using coherent light of substantially the same wavelength as the master laser source, and a coherent reference beam of substantially the same wavelength as the master laser source.
Versatile IEEE-488 data acquisition and control routines for a diode array spectrophotometer
Shiundu, Paul M.
The UV-visible diode array spectrophotometer is a work-horse instrument for many laboratories. This article provides simple data acquisition and control routines in Microsoft QuickBasic for a HP-8452A diode array spectrophotometer interfaced to an IBM PC/XT/AT, or compatible, microcomputer. These allow capture of full spectra and measure absorbance at one or several wavelengths at preset time intervals. The variance in absorbance at each wavelength is available as an option. PMID:18924888
Silicon carbide photomultipliers and avalanche photodiode arrays for ultraviolet and solar-blind light detection
Alexey Vert; Stanislav Soloviev; Alexander Bolotnikov; Peter Sandvik
Silicon carbide is known for its large bandgap and suitability to make highly sensitive ultraviolet photo-detectors. These devices show appreciable quantum efficiencies in the 240 nm - 350 nm wavelength range in combination with low dark currents. We present recent results on 4H-SiC avalanche photodiode arrays and SiC-based solid-state photomultiplier arrays suitable for ultraviolet and solar-blind light detection. A novel
Linewidth reduction of a broad-area laser diode array in a compound external cavity.
Liu, Bo; Liu, Yun; Braiman, Yehuda
A compound external cavity is designed and implemented to achieve a homogeneous spectrum distribution of broad area laser diodes in an array and to narrow the spectral linewidth of the entire array. The compound external cavity is composed of an optical coupler and a Littrow external cavity with a telescope along the fast axis. The inhomogeneous distribution of individual laser diodes spectrum generated by the "smile" effect was reduced by the telescope. The effective transverse coupling among individual laser diodes in an array was enhanced by the optical coupler, which further reduced the spectrum inhomogeneous distribution of the entire array. The spectral linewidth of a 49-emitter laser array is reduced to 0.1 nm at the output power of 12.5 W. PMID:19137048
Efficient compact watt-level deep-ultraviolet laser generated from a multi-kHz Q-switched diode-pumped
Kung, Andy
Efficient compact watt-level deep-ultraviolet laser generated from a multi-kHz Q-switched diode from a multi-kHz diode-pumped multi-longitudinal- mode Q-switched Nd:YAG laser by fourth harmonicŁ4], or a tightly focused, relatively complicated arrange- ment for compact diode-pumped systems [5Ł8]. Serious
Aluminium nanohole arrays enhanced resonance Raman scattering spectra in the near ultraviolet region
NASA Astrophysics Data System (ADS)
Wu, YanQing; Dong, Bin
Aluminium nanohole arrays with fixed diameter were fabricated by focused ion beam and the periodicities were turned. Aluminium nanohole arrays enhanced resonance Raman scattering spectra in the near ultraviolet region were studied experimentally and theoretically, which revealed that the SERRS enhancement factor was as high as 6 orders.
High-power pseudomorphic mid-ultraviolet light-emitting diodes with improved efficiency and lifetime
NASA Astrophysics Data System (ADS)
Moe, Craig G.; Grandusky, James R.; Chen, Jianfeng; Kitamura, Ken; Mendrick, Mark C.; Jamil, Muhammad; Toita, Masato; Gibb, Shawn R.; Schowalter, Leo J.
Recent advances in mid-ultraviolet light-emitting diodes grown pseudomorphically on bulk AlN substrates have led to improved efficiencies and lifetimes. For a 266 nm device an output power of 66 mW at 300 mA has been achieved with an external quantum efficiency of 4.5%. More importantly, the lifetimes of these devices have been increased substantially. Testing of LEDs in both surface mount design (SMD) and TO-39 packages show L50 lifetimes well in excess of 1,000 hours under a variety of case temperatures and currents. Package-related catastrophic failures are eliminated through encapsulation and hermetic sealing, further reducing failure rates and extending the lifetime.
Ultraviolet light emitting diodes and hydrogen peroxide in the photodegradation of aqueous phenol.
Vilhunen, Sari H; Sillanpõõ, Mika E T
The novel system of ultraviolet (UV) light emitting diodes (LED) and hydrogen peroxide (H(2)O(2)) was studied for the degradation of phenol as a model organic pollutant in water. The effect of different viewing angles (15 and 120 degrees ), wavelengths (255, 265 and 280 nm) and phenol and H(2)O(2) concentrations were investigated in four photolytic batch reactors. Phenol degradation was observed to be most efficient with UV LEDs emitting at wavelength 280 nm, presumably due to the highest optical power. However, quantum yield for 280 nm reactor was only 0.23 compared to 0.33 of 255 nm reactor. Quantum yields for the rest of the reactors were 0.24 (265 nm, 120 degrees ) and 0.22 (265 nm, 15 degrees ). UV LEDs in combination with hydrogen peroxide are promising in wastewater treatment in degrading organic compounds, though development of both LEDs and reactor design is needed. PMID:18555601
Uniformity of pump intensity distribution in diode-array side-pumped laser rod
NASA Astrophysics Data System (ADS)
Liu, Wenwen; Niu, Yanxiong; Liu, Haixia; Wang, Caili; Niu, Haisha; Man, Da
Diode-pumped solid-state lasers are high efficiency, long lifetime, compact and reliable, so they have been covering a wide range of applications. Thermal effect is a major limiting factor in scaling the average power of high-power solid-state lasers, so it is a critical issue in designing diode-pumped solid-state lasers. The uniform pump intensity distribution in laser rod can weaken the influence of thermal effects in laser, and the research of improving the pump distribution uniformity has attracted a great deal of attention. People usually establish a model of single diode-bar pumped laser rod to calculate the distribution. However, for diode-array pumped high-power lasers, the model is limited and has deviation with the actual pump distribution, which cannot reflect the real working conditions in the laser. In this paper, the theoretical model of diode-array pumped laser rod is built. Based on the actual working environment of diode-array side-pumped Tm:YAG laser rod, the expression of pump intensity distribution in the laser medium is deduced. Additionally, the influence of total pump power, pump structure, Tm:YAG rod characteristic parameters and pump beam radius on pump intensity distribution are simulated and analyzed. Moreover, the parameters are optimized in order to obtain the optimistic results which are efficient to improve the uniformity of pump distribution. The results show that when the pumping distance from diode-array to the rod's surface is 3mm, the distance between two rows of diode-bars is 1mm, the absorption coefficient is 330m-1,the pump beam width is 2.5mm,the pump intensity distribution of five-way pumped laser rod is improved, and then the thermal effects could be weakened. The presented results can provide theoretical guidance to design and optimization of high-power lasers.
High density, optically corrected, micro-channel cooled, v-groove monolithic laser diode array
Freitas, Barry L. (Livermore, CA)
An optically corrected, micro-channel cooled, high density laser diode array achieves stacking pitches to 33 bars/cm by mounting laser diodes into V-shaped grooves. This design will deliver>4kW/cm2 of directional pulsed laser power. This optically corrected, micro-channel cooled, high density laser is usable in all solid state laser systems which require efficient, directional, narrow bandwidth, high optical power density pump sources.
High density, optically corrected, micro-channel cooled, v-groove monolithic laser diode array
Freitas, B.L.
An optically corrected, micro-channel cooled, high density laser diode array achieves stacking pitches to 33 bars/cm by mounting laser diodes into V-shaped grooves. This design will deliver > 4kW/cm{sup 2} of directional pulsed laser power. This optically corrected, micro-channel cooled, high density laser is usable in all solid state laser systems which require efficient, directional, narrow bandwidth, high optical power density pump sources. 13 figs.
Fiber optic coupling of a microlens conditioned, stacked semiconductor laser diode array
Beach, Raymond J. (Livermore, CA); Benett, William J. (Livermore, CA); Mills, Steven T. (Antioch, CA)
The output radiation from the two-dimensional aperture of a semiconductor laser diode array is efficiently coupled into an optical fiber. The two-dimensional aperture is formed by stacking individual laser diode bars on top of another in a "rack and stack" configuration. Coupling into the fiber is then accomplished using individual microlenses to condition the output radiation of the laser diode bars. A lens that matches the divergence properties and wavefront characteristics of the laser light to the fiber optic is used to focus this conditioned radiation into the fiber.
Fiber optic coupling of a microlens conditioned, stacked semiconductor laser diode array
Beach, R.J.; Benett, W.J.; Mills, S.T.
The output radiation from the two-dimensional aperture of a semiconductor laser diode array is efficiently coupled into an optical fiber. The two-dimensional aperture is formed by stacking individual laser diode bars on top of another in a ``rack and stack`` configuration. Coupling into the fiber is then accomplished using individual microlenses to condition the output radiation of the laser diode bars. A lens that matches the divergence properties and wavefront characteristics of the laser light to the fiber optic is used to focus this conditioned radiation into the fiber. 3 figs.
Linear laser diode arrays for improvement in optical disk recording for space stations
NASA Technical Reports Server (NTRS)
Alphonse, G. A.; Carlin, D. B.; Connolly, J. C.
The design and fabrication of individually addressable laser diode arrays for high performance magneto-optic recording systems are presented. Ten diode arrays with 30 mW cW light output, linear light vs. current characteristics and single longitudinal mode spectrum were fabricated using channel substrate planar (CSP) structures. Preliminary results on the inverse CSP structure, whose fabrication is less critically dependent on device parameters than the CSP, are also presented. The impact of systems parameters and requirements, in particular, the effect of feedback on laser design is assessed, and techniques to reduce feedback or minimize its effect on systems performance, including mode-stabilized structures, are evaluated.
Improving Reliability of High Power Quasi-CW Laser Diode Arrays Operating in Long Pulse Mode
NASA Technical Reports Server (NTRS)
Amzajerdian, Farzin; Meadows, Byron L.; Barnes, Bruce W.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.; Baker, Nathaniel R.
Operating high power laser diode arrays in long pulse regime of about 1 msec, which is required for pumping 2-micron thulium and holmium-based lasers, greatly limits their useful lifetime. This paper describes performance of laser diode arrays operating in long pulse mode and presents experimental data of the active region temperature and pulse-to-pulse thermal cycling that are the primary cause of their premature failure and rapid degradation. This paper will then offer a viable approach for determining the optimum design and operational parameters leading to the maximum attainable lifetime.
Improving Lifetime of Quasi-CW Laser Diode Arrays for Pumping 2-Micron Solid State Lasers
NASA Technical Reports Server (NTRS)
Amzajerdian, Farzin; Meadows, Byron L.; Baker, Nathaniel R.; Barnes, Bruce W.; Singh, Upendra N.; Kavaya, Michael J.
Operating high power laser diode arrays in long pulse regime of about 1 msec, which is required for pumping 2-micron thulium and holmium-based lasers, greatly limits their useful lifetime. This paper describes performance of laser diode arrays operating in long pulse mode and presents experimental data on the active region temperature and pulse-to-pulse thermal cycling that are the primary cause of their premature failure and rapid degradation. This paper will then offer a viable approach for determining the optimum design and operational parameters leading to the maximum attainable lifetime.
Printed array of thin-dielectric metal-oxide-metal (MOM) tunneling diodes Mario Barei,1,a)
Grundler, Dirk
of different materials (e.g., metals and insulators8,9 ) was prepared on a stamp and then transferred ontoPrinted array of thin-dielectric metal-oxide-metal (MOM) tunneling diodes Mario Barei▀,1,a) Andreas area array of metal-oxide-metal (MOM) tunneling diodes with an ultrathin dielectric ($3.6 nm aluminum
Coherent addition of high power laser diode array with a V-shape external Talbot cavity.
Liu, B; Liu, Y; Braiman, Y
We designed a V-shape external Talbot cavity for a broad-area laser diode array and demonstrated coherent laser beam combining at high power with narrow spectral linewidth. The V-shape external Talbot cavity provides good mode-discrimination and does not require a spatial filter. A multi-lobe far-field profile generated by a low filling-factor phase-locked array is confirmed by our numerical simulation. PMID:19065232
Improved heat sinking for laser-diode arrays using microchannels in CVD diamond
Kenneth E. Goodson; Katsuo Kurabayashi; R. F. W. Pease
This work proposes a novel cooling system for high-power laser-diode arrays, for which the maximum optical output power density per unit surface area is limited by the temperature rise due to self-heating. The proposed system uses a microchannel heat sink made of chemical-vapor-deposited (CVD) diamond, whose high thermal conductivity increases the efficiency of the channel-wall fins and reduces the array-to-coolant
1352 OPTICS LETTERS / Vol. 25, No. 18 / September 15, 2000 Frequency-narrowed external-cavity diode-laser-array bar
Walker, Thad G.
1352 OPTICS LETTERS / Vol. 25, No. 18 / September 15, 2000 Frequency-narrowed external-cavity diode cavities can be used to frequency narrow high-power diode-array bars. Using a commercial 20-W array, we collimating lens minimize broadening owing to curvature in the alignment of the diode-array elements. ® 2000
A low-cost low-maintenance ultraviolet lithography light source based on light-emitting diodes.
Erickstad, M; Gutierrez, E; Groisman, A
A source of collimated ultraviolet (UV) light is a central piece of equipment needed for lithographic fabrication of microfluidic devices. Conventional UV light sources based on high-pressure mercury lamps require considerable maintenance and provide broad-band illumination with intensity that often changes with time. Here we present a source of narrow-band UV light based on an array of nine 365 nm light-emitting diodes (LEDs). Each LED has two dedicated converging lenses, reducing the divergence of light emanating from it to 5.4░. Partial overlap of the areas illuminated by individual LEDs provides UV illumination with a mean intensity of ~1.7 mW cm(-2) and coefficient of variation <3% over a 90 ū 90 mm target area. The light source was used to lithographically fabricate micro-reliefs with thicknesses from ~25 to 311 ?m with SU8 photoresists. A cumulative irradiation of 370 mJ cm(-2) (4 min exposure) produced reliefs of good quality for all SU8 thicknesses. Polydimethylsiloxane (PDMS) replicas of the SU8 reliefs had microchannels with nearly rectangular cross-sections that were highly consistent over the entire target area, and partitions between the channels had depth to width ratios up to 5. The UV light source has also been successfully used for photolithography with positive photoresists, AZ40XT and SPR-220. The proposed light source is built with a total cost of <$1000, consumes a minimal amount of power, is expected to last for ~50,000 exposures, is maintenance-free, and is particularly appealing for small research-and-development microfluidic fabrication. PMID:25322205
Performance of a TiN-coated monolithic silicon pin-diode array under mechanical stress
B. A. VanDevender; L. I. Bodine; A. W. Myers; J. F. Amsbaugh; M. A. Howe; M. L. Leber; R. G. H. Robertson; K. Tolich; T. D. Van Wechel; B. L. Wall
The Karlsruhe Tritium Neutrino Experiment (KATRIN) will detect tritium beta- decay electrons that pass through its electromagnetic spectrometer with a highly- segmented monolithic silicon pin-diode focal-plane detector (FPD). This pin-diode array will be on a single piece of 500-{\\mu}m-thick silicon, with contact between titanium nitride (TiN) coated detector pixels and front-end electronics made by spring-loaded pogo pins. The pogo pins will exert a total force of up to 50N on the detector, deforming it and resulting in mechanical stress up to 50 MPa in the silicon bulk. We have evaluated a prototype pin-diode array with a pogo-pin connection scheme similar to the KATRIN FPD. We find that pogo pins make good electrical contact to TiN and observe no effects on detector resolution or reverse-bias leakage current which can be attributed to mechanical stress.
Multianalyte sensor array based on an organic light emitting diode platform
Yuankun Cai; Ruth Shinar; Zhaoqun Zhou; Joseph Shinar
A compact photoluminescence (PL)-based sensor array, utilizing pulsed organic light emitting diode (OLED) pixels as the excitation sources, for sequential or simultaneous detection of multiple analytes in a single sample, is described. The utility and potential advantages of the structurally integrated OLED-based platform for multianalyte detection are demonstrated for oxygen, glucose, lactate, and ethanol. The detection of glucose, lactate, and
Field-programmable gate array based locking circuit for external cavity diode laser frequency stabilization
NASA Astrophysics Data System (ADS)
Schwettmann, Arne; Sedlacek, Jonathon; Shaffer, James P.
We present a locking circuit for external cavity diode lasers implemented on a field-programmable gate array (FPGA). The main advantages over traditional non-FPGA-based locking circuits are rapid reconfigurability without any soldering and a friendly user interface. We characterize the lock quality by measuring the linewidth of a locked laser using electromagnetically induced transparency in a Rb vapor cell.
A Lunar Optical-Ultraviolet-Infrared Synthesis Array (LOUISA)
NASA Technical Reports Server (NTRS)
Burns, Jack O. (editor); Johnson, Stewart W. (editor); Duric, Nebojsa (editor)
This document contains papers presented at a workshop held to consider 'optical ultraviolet infrared' interferometric observations from the moon. Part 1 is an introduction. Part 2 is a description of current and planned ground-based interferometers. Part 3 is a description of potential space-based interferometers. Part 4 addresses the potential for interferometry on the moon. Part 5 is the report of the workshop's working groups. Concluding remarks, summary, and conclusions are presented in Part 6.
High-performance liquid chromatography¢diode array and electrospray-mass spectrometry analysis of non-allowed substances in cosmetic products for preventing hair loss and other hormone-dependent skin diseases
Daniela De Orsi; Manuela Pellegrini; Simona Pichini; Donatella Mattioli; Emilia Marchei; Luigi Gagliardi
A simple high-performance liquid chromatography (HPLC) method with ultraviolet diode array (UV-DAD) and electrospray ionisation mass spectrometry (ESI-MS) detection has been developed for the determination of minoxidil, progesterone, estrone, spironolactone, canrenone, hydrocortisone and triamcinolone acetonide in cosmetic products. The presence of these substances in commercial cosmetic samples is prohibited. The compounds were separated by reversed phase chromatography with water (0.1%
Physics of aligned arrays of single-walled NTs: From transistor to diode applications
NASA Astrophysics Data System (ADS)
Rotkin, Slava V.; Rogers, John A.
NTs have been originally proposed as a 1D high mobility semiconductor material for field-effect transistors (FET). This format is though appeared to be less practical due to low values of the currents through a single NT channel. On contrary, NT massive parallel arrays have already found implementation in flexible and RF electronics. Can we think of NT arrays being another semiconductor thin film materials? Where does the conventional knowledge apply for NT parallel array devices? This talk discusses specialized aspects of physics of electronic and optoelectronic device prototypes and presents recent results for NT FETs and LEDs (light-emitting diode) in parallel array geometries. Cross-talk between individual NTs in the array allows to beat the statistical ``noise'' in the device properties which appears due to randomized NT distribution in the array. Although, taking this into account, device-level characteristics should be used with a care to extract a single NT physical parameters.
Arto V. Nurmikko; Jung Han
We report on research results in this project which synergize advanced material science approaches with fundamental optical physics concepts pertaining to light-matter interaction, with the goal of solving seminal problems for the development of very high performance light emitting diodes (LEDs) in the blue and near ultraviolet for Solid State Lighting applications. Accomplishments in the first 12 month contract period include (1) new means of synthesizing zero- and one-dimensional GaN nanostructures, (2) establishment of the building blocks for making GaN-based microcavity devices, and (3) demonstration of top-down approach to nano-scale photonic devices for enhanced spontaneous emission and light extraction. These include a demonstration of eight-fold enhancement of the external emission efficiency in new InGaN QW photonic crystal structures. The body of results is presented in this report shows how a solid foundation has been laid, with several noticeable accomplishments, for innovative research, consistent with the stated milestones.
High-Power Genuine Ultraviolet Light-Emitting Diodes Based On Colloidal Nanocrystal Quantum Dots.
Kwak, Jeonghun; Lim, Jaehoon; Park, Myeongjin; Lee, Seonghoon; Char, Kookheon; Lee, Changhee
Thin-film ultraviolet (UV) light-emitting diodes (LEDs) with emission wavelengths below 400 nm are emerging as promising light sources for various purposes, from our daily lives to industrial applications. However, current thin-film UV-emitting devices radiate not only UV light but also visible light. Here, we introduce genuine UV-emitting colloidal nanocrystal quantum dot (NQD) LEDs (QLEDs) using precisely controlled NQDs consisting of a 2.5-nm-sized CdZnS ternary core and a ZnS shell. The effective core size is further reduced during the shell growth via the atomic diffusion of interior Cd atoms to the exterior ZnS shell, compensating for the photoluminescence red shift. This design enables us to develop CdZnS@ZnS UV QLEDs with pure UV emission and minimal parasitic peaks. The irradiance is as high as 2.0-13.9 mW cm(-2) at the peak wavelengths of 377-390 nm, several orders of magnitude higher than that of other thin-film UV LEDs. PMID:25961530
AlGaN-based ultraviolet light-emitting diodes grown on AlN epilayers
Kim, K.H.; Fan, Z.Y.; Khizar, M.; Nakarmi, M.L.; Lin, J.Y.; Jiang, H.X. [Department of Physics, Kansas State University, Manhattan, Kansas 66506-2601 (United States)
AlGaN-based deep-ultraviolet light-emitting diode (LED) structures, which radiate light at 305 and 290 nm, have been grown on sapphire substrates using an AlN epilayer template. The fabricated devices have a circular geometry to enhance current spreading and light extraction. Circular UV LEDs of different sizes have been characterized. It was found that smaller disk LEDs had higher saturation optical power densities but lower optical powers than the larger devices. This trade-off between power and power density is a result of a compromise between electrical and thermal resistance, as well as the current crowding effect (which is due to the low electrical conductivity of high aluminum composition n- and p-AlGaN layers). Disk UV LEDs should thus have a moderate size to best utilize both total optical power and power density. For 0.85 mmx0.85 mm interdigitated LEDs, a saturation optical power of 2.9 mW (1.8 mW) at 305 nm (290 nm) was also obtained under dc operation.
Development of substrate-removal-free vertical ultraviolet light-emitting diode (RefV-LED)
Kurose, N., E-mail: firstname.lastname@example.com; Aoyagi, Y. [The Research Organization of Science and Technology, Ritsumeikan University, 1-1-1, Noji-higashi, Kusatsu, Shiga 525-8577 (Japan)] [The Research Organization of Science and Technology, Ritsumeikan University, 1-1-1, Noji-higashi, Kusatsu, Shiga 525-8577 (Japan); Shibano, K.; Araki, T. [Department of Science and Technology, Ritsumeikan University, 1-1-1, Noji-higashi, Kusatsu, Shiga 525-8577 (Japan)] [Department of Science and Technology, Ritsumeikan University, 1-1-1, Noji-higashi, Kusatsu, Shiga 525-8577 (Japan)
A vertical ultraviolet (UV) light-emitting diode (LED) that does not require substrate removal is developed. Spontaneous via holes are formed in n-AlN layer epitaxially grown on a high conductive n+Si substrate and the injected current flows directly from the p-electrode to high doped n{sup +} Si substrate through p-AlGaN, multi-quantum wells, n-AlGaN and spontaneous via holes in n-AlN. The spontaneous via holes were formed by controlling feeding-sequence of metal-organic gas sources and NH{sub 3} and growth temperature in MOCVD. The via holes make insulating n-AlN to be conductive. We measured the current-voltage, current-light intensity and emission characteristics of this device. It exhibited a built-in voltage of 3.8 V and emission was stated at 350 nm from quantum wells with successive emission centered at 400?nm. This UV LED can be produced, including formation of n and p electrodes, without any resist process.
Laser processing of gallium nitride-based light-emitting diodes with ultraviolet picosecond laser pulses
NASA Astrophysics Data System (ADS)
Moser, R³diger; Kunzer, Michael; Go▀ler, Christian; K÷hler, Klaus; Pletschen, Wilfried; Schwarz, Ulrich T.; Wagner, Joachim
The fabrication of optoelectronic devices such as light-emitting diodes (LEDs) typically involves photolithography steps, requiring specific lithography masks. This approach is expensive, inflexible and time consuming, in particular for prototyping. Therefore it would be attractive to replace these steps by direct writing techniques such as laser processing, which would speed up, for example the development and prototyping of new devices. Picosecond lasers provide a universal tool for material processing. Due to the short pulse length, material is removed by a process called "cold ablation," with minimal thermal damage to neighboring regions. As a result, better-defined structures with smoother and cleaner side walls can be fabricated compared to nanosecond-pulsed laser-based processing. We report on fully laser-processed planar gallium nitride-based LEDs fabricated using only ps laser processing for pattern definition and material removal. On the bare semiconductor wafer, isolation trenches and mesa structures are formed directly by ultraviolet ps laser pulse writing. For the direct deposition of patterned ohmic contact metallizations, the ps laser fabrication and subsequent use of high-resolution shadow masks is presented. Finally, the ps laser-processed LEDs are electrically and optically characterized and their characteristics compared with those of conventionally fabricated mesa LEDs.
Investigation of ZnO-based ultraviolet light-emitting diodes
NASA Astrophysics Data System (ADS)
Lee, Ching-Ting; Chang, Hao-Yu
Recently, ZnO-based semiconductors have been deposited on various substrates using various methods. Furthermore, they were used in ultraviolet light-emitting diodes (UVLEDs) due to inherent properties including wide direct bandgap and high binding energy. In this work, two different deposition systems were utilized to deposit the ZnO-based films. The resulted films were applied to fabricate the ZnO-based UVLEDs. Firstly, the high quality i-ZnO films were deposited as the active layer by using the vapor cooling condensation system to enhance the internal quantum efficiency. Secondly, the double-heterostructured MgZnO/ZnO/MgZnO layers were deposited as the active layer at low temperature using the vapor cooling condensation system to enhance light intensity. Furthermore, various component ratios of i- MgZnO and i-MgBeZnO films were deposited using a radio frequency (RF) magnetron co-sputter system. Consequently, the deposited films with various energy bandgaps were stacked alternately to form the active layer of multiple-quantum well (MQW) UVLEDs. The light emitting intensity of MQW UVLEDs was better than that of the traditional p-i-n UVLEDs. This phenomenon was attributed to the carrier confinement in well layers and improvement probability of radiative recombination.
Phase-delayed laser diode array allows ultrasonic guided wave mode selection and tuning
NASA Astrophysics Data System (ADS)
Karppinen, Pasi; Salmi, Ari; Moilanen, Petro; Karppinen, Timo; Zhao, Zuomin; Myllylõ, Risto; Timonen, Jussi; Hµggstr÷m, Edward
Selecting and tuning modes are useful in ultrasonic guided wave non-destructive testing (NDT) since certain modes at various center frequencies are sensitive to specific types of defects. Ideally one should be able to select both the mode and the center frequency of the launched waves. We demonstrated that an affordable laser diode array can selectively launch either the S0 or A0 ultrasonic wave mode at a chosen center frequency into a polymer plate. A fiber-coupled diode array (4 elements) illuminated a 2 mm thick acrylic plate. A predetermined time delay matching the selected mode and frequency was employed between the output of the elements. The generated ultrasound was detected by a 215 kHz piezo receiver. Our results imply that this array permits non-contacting guided wave ultrasonic NDT. The solution is small, affordable, and robust in comparison to conventional pulsed lasers. In addition, it does not require experienced operators.
Resonant self-aligned-stripe antiguided diode laser array
L. J. Mawst; D. Botez; C. Zmudzinski; M. Jansen; C. Tu; T. J. Roth; J. Yun
Resonant-optical-waveguide arrays with a self-aligned-stripe geometry have been realized for the first time. Resonance is achieved by holding the array element\\/interelement widths constant and varying the aluminum composition of the passive guide layer. External differential quantum efficiencies as high as 47 percent have been achieved from longitudinally uniform 20-element 1000-micron-long devices. Diffraction-limited-beam operation is obtained up to 13 x threshold,
Qualification Testing of Laser Diode Pump Arrays for a Space-Based 2-micron Coherent Doppler Lidar
NASA Technical Reports Server (NTRS)
Amzajerdian, Farzin; Meadows, Byron L.; Baker, Nathaniel R.; Barnes, Bruce W.; Singh, Upendra N.; Kavaya, Michael J.
The 2-micron thulium and holmium-based lasers being considered as the transmitter source for space-based coherent Doppler lidar require high power laser diode pump arrays operating in a long pulse regime of about 1 msec. Operating laser diode arrays over such long pulses drastically impact their useful lifetime due to the excessive localized heating and substantial pulse-to-pulse thermal cycling of their active regions. This paper describes the long pulse performance of laser diode arrays and their critical thermal characteristics. A viable approach is then offered that allows for determining the optimum operational parameters leading to the maximum attainable lifetime.
Improvement in Outcoupling Efficiency and Image Blur of Organic Light-Emitting Diodes by Using Imprinted Microlens Arrays
Jin Yeong Kim; Kyung Cheol Choi
We demonstrated a new approach to fabricate microlens arrays attached to an organic light-emitting diode (OLED) to improve the outcoupling efficiency. Polydimethyl- siloxane (PDMS) microlens arrays were fabricated by imprint lithography. Two kinds of photoresists were used to make a mold to imprint the microlens array. Using this simple and low-cost fabrication process, a maximum of 43% luminance enhancement was
1.1-W cw Cr:LiSAF laser pumped by a 1-cm diode array
D. Kopf; U. Keller; M. A. Emanuel; R. J. Beach; J. A. Skidmore
We demonstrate 1.1-W cw output power from a diode-laser array-pumped Cr:LiSAF laser based on a concept that allows for pumping low-gain solid-state lasers at reduced temperature rise. We discuss scaling to higher powers as a function of diode power and define a figure of merit for evaluating given diode lasers as pump sources for low-gain solid-state lasers. {copyright} {ital 1997}
Extraction of real-space correlation function of a rough surface by light scattering using diode array detectors
Wang, Gwo-Ching
Extraction of real-space correlation function of a rough surface by light scattering using diode distribution profile of light scattering. A novel diode array detectors arrangement was used to obtain-ray dif- fraction, atom diffraction, and light scattering, are also useful in the quantitative study
Duty cycle effects on intensity and wavelength fluctuations in a pulsed variable spacing phase-locked laser diode array
Fuhr, P.L.; Davidson, F.M.
Wavelength and intensity fluctuations in the output of a variable spacing phase-locked laser diode array were investigated. The diode was pulsed at duty cycles appropriate for low order optical pulse position modulation signaling. Both the spectral width and intensity fluctuation levels were observed to increase as the duty cycle was increased.
240 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 20, NO. 4, FEBRUARY 15, 2008 A Novel Ordered Nanopore Array Diode Laser
Coleman, James J.
October 21, 2007. This work was supported in part by the Defense Advanced Research Projects Agency (DARPA Array Diode Laser V. C. Elarde, Student Member, IEEE, and J. J. Coleman, Member, IEEE Abstract Terms--Diode laser, nanopore, periodic perturbation, quantization, semiconductor laser. I. INTRODUCTION
Injection locking of a fiber-coupled laser diode array M.A. Humphrey, J.E. Massey, D.F. Phillips, and R.L. Walsworth
Walsworth, Ronald L.
, fiber-coupled laser diode array was significantly narrowed by injection locking. Up to 72% of the 1 THz for narrowing the spectral output of high power, non-fiber-coupled diode lasers. Optical feedback may1 Injection locking of a fiber-coupled laser diode array M.A. Humphrey, J.E. Massey, D.F. Phillips
High Power Density Beam from Narrow Diode-Laser Arrays in Axial Symmetry
Taito Alahautala; Erkki Lassila; Rolf Hernberg
A multiplexing method based on narrow diode-laser arrays (DLAs) in an axially symmetric configuration is described. The use of submillimeter narrow DLAs improves beam quality considerably in the slow-axis direction compared with typical 1-cm-wide DLAs. The axially symmetric geometry is advantageous for efficient spatial, wavelength, and polarization multiplexing. With narrow DLAs and an axially symmetric geometry, a small circular focus
Identification of natural dyes in archeological Coptic textiles by liquid chromatography with diode array detection
Jowita Orska-Gawry?; Izabella Surowiec; Jerzy Kehl; Hanna Rejniak; Katarzyna Urbaniak-Walczak; Marek Trojanowicz
Reversed-phase HPLC with diode-array UV¢Vis spectrophotometric detection has been used for identification of natural dyes in extracts from wool and silk fibres from archeological textiles. The examined objects originate from 4th to 12th Century Egypt and belong to the collection of Early Christian Art of the National Museum in Warsaw. Extraction from fibres was carried out with HCl solution containing
Field-programmable gate array based locking circuit for external cavity diode laser frequency stabilization.
Schwettmann, Arne; Sedlacek, Jonathon; Shaffer, James P
We present a locking circuit for external cavity diode lasers implemented on a field-programmable gate array (FPGA). The main advantages over traditional non-FPGA-based locking circuits are rapid reconfigurability without any soldering and a friendly user interface. We characterize the lock quality by measuring the linewidth of a locked laser using electromagnetically induced transparency in a Rb vapor cell. PMID:22047276
Beam vignetting effect in micro-optic collimation and transmission for high power diode laser arrays
NASA Astrophysics Data System (ADS)
Forrer, H.; Moser, H.; Huber, M.; Kura, D.; Schmidlin, M.; Mourad, S.; Forrer, M.
High power diode laser arrays need special micro-optic beamshaping to optimize for collimation and spot focusing. A known and established solution makes use of cylindrical micro- optics for fast axis collimation and subsequent individual twisting of each emitter beamlet by a micro-optic cylindrical telescope array in order to achieve a symmetric beam parameter product. A crucial factor for the overall performance is the achievable transmission to collimation and the fiber coupling efficiency. We present an optical analysis of vignetting effects on the transmission in the beam twisting setup and show an optimization which can be achieved by advanced micro-optic production technologies.
Ultraviolet emission from a multi-layer graphene/MgZnO/ZnO light-emitting diode
Kang, Jang-Won; Choi, Yong-Seok; Goo Kang, Chang; Hun Lee, Byoung [School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Kim, Byeong-Hyeok [Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Tu, C. W. [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093-0407 (United States); Park, Seong-Ju, E-mail: email@example.com [School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of)
We report on ultraviolet emission from a multi-layer graphene (MLG)/MgZnO/ZnO light-emitting diodes (LED). The p-type MLG and MgZnO in the MLG/MgZnO/ZnO LED are used as transparent hole injection and electron blocking layers, respectively. The current-voltage characteristics of the MLG/MgZnO/ZnO LED show that current transport is dominated by tunneling processes in the MgZnO barrier layer under forward bias conditions. The holes injected from p-type MLG recombine efficiently with the electrons accumulated in ZnO, and the MLG/MgZnO/ZnO LED shows strong ultraviolet emission from the band edge of ZnO and weak red-orange emission from the deep levels of ZnO.
Ultraviolet upconversion fluorescence in rare-earth-ion-doped Y2O3 induced by infrared diode laser excitation.
Chen, G Y; Somesfalean, G; Zhang, Z G; Sun, Q; Wang, F P
Room-temperature ultraviolet emission of Tm(3+) ions at 298 ((1)I(6)-->(3)H(6)), 364 ((1)D(2)-->(3)H(6)), and 391 nm ((1)I(6)-->(3)H(5)) was obtained in Y(2)O(3):Yb(3+)-Tm(3+) by continuous-wave diode laser excitation of 980 nm. Power dependence analysis demonstrates that five- and six-photon upconversion processes populate the (1)D(2) and (1)I(6) states, respectively. We believe that the (1)D(2) population originates from the cross relaxation (1)G(4)+(3)F(4)-->(3)H(4)+(1)D(2) of the Tm(3+) ions, while subsequent energy transfer from Yb(3+) to Tm(3+) excites the (1)D(2) state to the upper (1)I(6) state. High multiphoton-induced ultraviolet emission is also expected for other trivalent rare-earth ions similar to Tm(3+). PMID:17167593
Graphene-silver nanowire hybrid structure as a transparent and current spreading electrode in ultraviolet light emitting diodes
NASA Astrophysics Data System (ADS)
Hoon Seo, Tae; Kyoung Kim, Bo; Shin, GangU; Lee, Changhyup; Jong Kim, Myung; Kim, Hyunsoo; Suh, Eun-Kyung
We report a device that combines graphene film and Ag nanowires (AgNWs) as transparent and current spreading electrodes for ultra-violet (UV) light emitting diode (LED) with interesting characteristics for the potential use in the deep UV region. The current-voltage characteristics and electroluminescence (EL) performance show that graphene network on AgNWs well-operates as a transparent and current spreading electrode in UV LED devices. In addition, scanning electron microscopy and EL images exhibit that graphene film act as the protection layer of AgNWs layer as well as a transparent conducting network, by bridging AgNWs.
Feasibility of ultraviolet-light-emitting diodes as an alternative light source for photocatalysis.
Levine, Lanfang H; Richards, Jeffrey T; Coutts, Janelle L; Soler, Robert; Maxik, Fred; Wheeler, Raymond M
The objective of this study was to determine whether ultraviolet-light-emitting diodes (UV-LEDs) could serve as an efficient photon source for heterogeneous photocatalytic oxidation (PCO). An LED module consisting of 12 high-power UV-A (lambda max = 365 nm) LEDs was designed to be interchangeable with a UV-A fluorescent black light blue (BLB) lamp for a bench scale annular reactor packed with silica-titania composite (STC) pellets. Lighting and thermal properties of the module were characterized to assess its uniformity and total irradiance. A forward current (I(F)) of 100 mA delivered an average irradiance of 4.0 mW cm(-2) at a distance of 8 mm, which is equivalent to the maximum output of the BLB, but the irradiance of the LED module was less uniform than that of the BLB. The LED and BLB reactors were tested for the oxidization of ethanol (50 ppm(v)) in a continuous-flow-through mode with 0.94 sec residence time. At the same average irradiance, the UV-A LED reactor resulted in a lower CO2 production rate (19.8 vs. 28.6 nmol L(-1) s(-1)), lower ethanol removal (80% vs. 91%), and lower mineralization efficiency (28% vs. 44%) than the UV-A BLB reactor. Ethanol mineralization was enhanced with the increase of the irradiance at the catalyst surface. This result suggests that reduced ethanol mineralization in the LED reactor relative to the BLB reactor at the same average irradiance could be attributed to the nonuniform irradiance over the photocatalyst, that is, a portion of the catalyst was exposed to less than the average irradiance. The potential of UV-A LEDs may be fully realized by optimizing the light distribution over the catalyst and utilizing their instantaneous "on" and "off" feature for periodic irradiation. Nevertheless, our results also showed that the current UV-A LED module had the same wall plug efficiency (WPE) of 13% as that of the UV-A BLB, demonstrating that UV-A LEDs are a viable photon source both in terms of WPE and PCO efficiency. PMID:22010378
The development and application of a diode-laser-based ultraviolet absorption sensor for nitric oxide
Anderson, Thomas Nathan
by the NO molecule to determine the concentration via optical absorption spectroscopy. UV radiation at 226.8 nm is generated by sum frequency mixing the outputs from a 395-nm external cavity diode laser (ECDL) and a 532-nm diode-pumped, intracavity frequency doubled...
10?m pitch design of HgCdTe diode array in Sofradir
NASA Astrophysics Data System (ADS)
Pķrķ-Laperne, Nicolas; Rubaldo, Laurent; Kerlain, Alexandre; CarrĶre, Emmanuel; Dargent, Lo'c.; Taalat, Rachid; Berthoz, Jocelyn
Sofradir recently presented Daphnis, its latest 10?m pitch XGA and HD720 products. Daphnis XGA is a 10?m pitch 1024x768 mid-wave infrared focal plane array. The development of small pixel pitch is opening the way to very compact products with high spatial resolution. This new product is key contribution to the HOT technology competition allowing reductions in size, weight and power of the overall package. This paper presents the recent developments achieved at Sofradir to make this 10?m pitch HgCdTe focal plane array. Electrical and electro-optical characterizations are presented to define the appropriate design of 10?m pitch diode array. The technological tradeoffs are explained to lower the dark current, to keep high quantum efficiency with a high operability above 110K, F/4.
A photon-counting photodiode array detector for far ultraviolet (FUV) astronomy
NASA Astrophysics Data System (ADS)
Hartig, G. F.; Moos, H. W.; Pembroke, R.; Bowers, C.
A compact, stable, single-stage intensified photodiode array detector designed for photon-counting, far ultraviolet astronomy applications employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain pulses with a narrowly peaked pulse height distribution. The P-20 output phosphor exhibits a very short decay time, due to the high current density of the electron pulses. This intensifier is being coupled to a self-scanning linear photodiode array which has a fiber optic input window which allows direct, rigid mechanical coupling with minimal light loss. The array was scanned at a 250 KHz pixel rate. The detector exhibits more than adequate signal-to-noise ratio for pulse counting and event location.
A photon-counting photodiode array detector for far ultraviolet (FUV) astronomy
NASA Technical Reports Server (NTRS)
Hartig, G. F.; Moos, H. W.; Pembroke, R.; Bowers, C.
A compact, stable, single-stage intensified photodiode array detector designed for photon-counting, far ultraviolet astronomy applications employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain pulses with a narrowly peaked pulse height distribution. The P-20 output phosphor exhibits a very short decay time, due to the high current density of the electron pulses. This intensifier is being coupled to a self-scanning linear photodiode array which has a fiber optic input window which allows direct, rigid mechanical coupling with minimal light loss. The array was scanned at a 250 KHz pixel rate. The detector exhibits more than adequate signal-to-noise ratio for pulse counting and event location.
A superconducting focal plane array for ultraviolet, optical, and near-infrared astrophysics
Mazin, Benjamin A; Meeker, Seth R; O'Brien, Kieran; McHugh, Sean; Langman, Eric
Microwave Kinetic Inductance Detectors, or MKIDs, have proven to be a powerful cryogenic detector technology due to their sensitivity and the ease with which they can be multiplexed into large arrays. A MKID is an energy sensor based on a photon-variable superconducting inductance in a lithographed microresonator, and is capable of functioning as a photon detector across the electromagnetic spectrum as well as a particle detector. Here we describe the first successful effort to create a photon-counting, energy-resolving ultraviolet, optical, and near infrared MKID focal plane array. These new Optical Lumped Element (OLE) MKID arrays have significant advantages over semiconductor detectors like charge coupled devices (CCDs). They can count individual photons with essentially no false counts and determine the energy and arrival time of every photon with good quantum efficiency. Their physical pixel size and maximum count rate is well matched with large telescopes. These capabilities enable powerful new astrophy...
Monolithic multichannel ultraviolet detector arrays and continuous phase evolution in MgxZn1xO composition spreads
Rubloff, Gary W.
whose potential device applications include UV lasers,1,2 transparent con- ducting films for solar cellsMonolithic multichannel ultraviolet detector arrays and continuous phase evolution in MgxZn1└x the spread is used as a basis for compact broadband photodetector arrays with a range of detection
A digital optical phase-locked loop for diode lasers based on field programmable gate array
Xu Zhouxiang; Zhang Xian; Huang Kaikai; Lu Xuanhui [Physics Department, Zhejiang University, Hangzhou, 310027 (China)
We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382/MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat note line width below 1 Hz, residual mean-square phase error of 0.14 rad{sup 2} and transition time of 100 {mu}s under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.
Integrated injection-locked high-power cw diode laser arrays
Hohimer, J. P.; Myers, D. R.; Brennan, T. M.; Hammons, B. E.
We report the first integrated injection-locked high-power continuous-wave diode laser array with an on-chip independently controlled master laser. This device emits a near-diffraction-limited (0.5/degree/ full width at half maximum) single-lobed far-field emission beam at single-facet powers up to 125 mW. Also, by current tuning the emission wavelength of the master laser, we observe steering of the single-lobed emission over an angular range of 0.50/degree/ at a rate of /minus/1.2/times/10/sup /minus/2/ deg/mA. Our work demonstrates the feasibility of incorporating active optical injection and control in the structure of high-power diode laser devices.
Characteristics of ultraviolet nonpolar InGaN/GaN light-emitting diodes using trench epitaxial lateral overgrowth technology
NASA Astrophysics Data System (ADS)
Ling, Shih-Chun; Wang, Te-Chung; Ko, Tsung-Shine; Lu, Tien-Chang; Kuo, Hao-Chung; Wang, Shing-Chung
Ultraviolet nonpolar InGaN/GaN light-emitting diodes grown on trench epitaxial lateral overgrowth (TELOG) a-plane GaN template by metalorganic chemical vapor deposition were fabricated. Two emission peaks at 373 and 443 nm are observed from each fabricated device. The double emission peaks feature is identified by cathodoluminescence images, which show that the ultraviolet peak is emitted from the low-defect density wings on the TELOG and the blue peak is emitted from the TELOG-coalesced seed areas due to different incorporation of indium. The L-I-V diagram revealed that there are leakage current pathways due to the many threading dislocations in seed regions, and that the output power reached 0.2 mW at 140 mA. Two electroluminescence (EL) peaks are observed simultaneously when the driving current is below 50 mA. However, the EL peak at 373 nm dominates when current is above 50 mA. In addition, the degree of polarization of the ultraviolet peak was measured and found to be 28.7%.
Enhancement of light extraction efficiency of InGaN quantum wells light emitting diodes using Si O 2 /polystyrene microlens arrays
Gilchrist, James F.
Enhancement of light extraction efficiency of InGaN quantum wells light emitting diodes using Si O of InGaN quantum wells light emitting diodes using SiO2/polystyrene microlens arrays Yik-Khoon Ee November 2007 Improvement of light extraction efficiency of InGaN quantum wells light emitting diodes LEDs
Investigation of spectra unfolded for a filtered x-ray diode array with improved smoothness.
Li, Jing; Huang, Xian-Bin; Zhang, Si-Qun; Yang, Li-Bing; Xie, Wei-Ping; Pu, Yi-Kang
An unfolding algorithm using parabolic B-splines to smoothly reconstruct the soft x-ray spectra from the measurements of a filtered x-ray diode array is proposed. This array has been fabricated for the study of the soft x ray emitted by Z-pinch plasma. Unfolding results show that for the simulated noise-free blackbody spectra with temperature ranging from 20 to 250 eV, both the spectra and the total power are accurately recovered. Typical experimental waveforms along with the unfolded spectra and total power of x rays are presented. Possible defects due to the adoption of parabolic B-splines instead of conventionally used histograms are discussed. PMID:19566195
QCW diode array reliability at 80x and 88x nm
NASA Astrophysics Data System (ADS)
Feeler, Ryan; Junghans, Jeremy; Levy, Joseph; Schnurbusch, Don; Stephens, Ed
Northrop Grumman Cutting Edge Optronics (NGCEO) has recently developed high-power laser diode arrays specifically for long-life operation in quasi-CW applications. These arrays feature a new epitaxial wafer design that utilizes a large optical cavity and are packaged using AuSn solder and CTE-matched heat sinks. This work focuses on life test matrix of multiple epitaxial structures, multiple wavelengths, and multiple drive currents. Particular emphasis is given to the 80x and 88x wavelength bands running at 100-300 Watts per bar. Reliable operating points are identified for various applications including range finding (product lifetimes less than 1 billion shots) and industrial machining (product lifetimes greater than 20 billion shots). In addition to life test data, a summary of performance data for each epitaxial structure and each bar design is also presented.
Multiple detector focal plane array ultraviolet spectrometer for the AMPS laboratory
NASA Technical Reports Server (NTRS)
Feldman, P. D.
The possibility of meeting the requirements of the amps spectroscopic instrumentation by using a multi-element focal plane detector array in a conventional spectrograph mount was examined. The requirements of the detector array were determined from the optical design of the spectrometer which in turn depends on the desired level of resolution and sensitivity required. The choice of available detectors and their associated electronics and controls was surveyed, bearing in mind that the data collection rate from this system is so great that on-board processing and reduction of data are absolutely essential. Finally, parallel developments in instrumentation for imaging in astronomy were examined, both in the ultraviolet (for the Large Space Telescope as well as other rocket and satellite programs) and in the visible, to determine what progress in that area can have direct bearing on atmospheric spectroscopy.
Regularly-patterned nanorod light-emitting diode arrays grown with metalorganic vapor-phase epitaxy
NASA Astrophysics Data System (ADS)
Tu, Charng-Gan; Su, Chia-Ying; Liao, Che-Hao; Hsieh, Chieh; Yao, Yu-Feng; Chen, Hao-Tsung; Lin, Chun-Han; Chen, Horng-Shyang; Kiang, Yean-Woei; Yang, C. C.
The growth and fabrication of GaN nanorod (NR) light-emitting diode (LED) arrays have attracted much attention because of their advantages of higher crystal quality, larger sidewall emission area, and non-polar or semi-polar quantum well (QW) formation. In this paper, we review the development of regularly-patterned GaN NR LED arrays grown with metalorganic vapor-phase epitaxy. Such an array device is expected to be useful for practical lighting application. A regularly-patterned NR array is grown on a patterned template with either continuous or pulsed growth mode. Usually, with the pulsed growth mode, by switching group-III and V sources on and off alternatively, the NR geometry can be more uniform over an array. InGaN/GaN QWs can be deposited on the c-plane top face, m-plane sidewalls, and { 1 1 bar 0 1 } -plane slant facets on a c-axis-oriented NR with the highest (lowest) growth rate in the c-plane ({ 1 1 bar 0 1 } -plane). After the overgrowth of p-GaN on an NR with n-GaN core and QW deposition, an NR LED array can be implemented by covering the NRs with a transparent conductor. It has been demonstrated that the optical and electrical performances of an NR LED array can be comparable to those of a planar LED. Further developments in NR LED growth and process techniques can lead to an outperforming LED device with the NR structure.
Manufacture of brightness enhancement films (BEFs) by ultraviolet (UV) irradiation and their applications for organic light emitting diodes (OLEDs)
Jian-Shian Lin; Shih-Hsun Lin; Nien-Po Chen; Cheng-Hao Ko; Zong-Sian Tsai; Fuh-Shyang Juang; Chen-Ming Chen; Lung-Chang Liu
By ultraviolet (UV) irradiation, brightness enhancement films (BEFs) have been successfully manufactured with UV-curable polymers and applied for organic light emitting diodes (OLEDs).With BEFs, either green OLEDs (BEF\\/ITO glass\\/NPB (30nm)\\/Alq3 (65nm)\\/LiF (0.5nm)\\/Al (100nm)) or white OLEDs (BEF\\/ITO glass\\/TAPC (40nm)\\/mCP:Os:Firpic mixture (weight ratio=82:17:1; 25nm)\\/BCP (15nm)\\/Alq3 (30nm)\\/LiF (0.5nm)\\/Al(150nm)) exhibit better electroluminescent performances than those without BEFs. In case of green OLEDs, the
Performance enhancement of AlGaN-based ultraviolet light-emitting diodes by tailoring polarization in electron blocking layer
NASA Astrophysics Data System (ADS)
Yang, Guofeng; Chang, Jianjun; Wang, Jin; Zhang, Qing; Xie, Feng; Xue, Junjun; Yan, Dawei; Wang, Fuxue; Chen, Peng; Zhang, Rong; Zheng, Youdou
The AlGaN-based ultraviolet light-emitting diodes (UV LEDs) with specific design of graded AlGaN electron blocking layer (EBL) are investigated numerically. The light output power of LEDs with tailored graded AlGaN EBL is markedly improved. Simulation analysis shows that via proper modification of polarization field from the last barrier of the active region to EBL, not only the elimination of electron overflow to p-type layer can be achieved, but also the hole injection into the active region can be enhanced. The enhanced performance for tailored UV LED is explained by the simulated energy band diagrams, distribution of carrier concentration and radiative recombination rate in the quantum wells.
Performance improvement of AlGaN-based deep ultraviolet light-emitting diodes by using staggered quantum wells
NASA Astrophysics Data System (ADS)
Zhang, Min; Li, Yang; Chen, Shengchang; Tian, Wu; Xu, Jintong; Li, Xiangyang; Wu, Zhihao; Fang, Yanyan; Dai, Jiangnan; Chen, Changqing
The optical and physical properties of AlGaN-based deep ultraviolet light-emitting diodes (UV LEDs) with various specific designs of staggered quantum wells (QWs) are numerically investigated. Detailed analysis has been carried out on the light output power, energy band, overlap of electron and hole wavefunctions, carrier concentration, radiative recombination rate, spontaneous radiative spectrum and internal quantum efficiency. The simulated results reveal that the deep UV LEDs with the staggered quantum wells exhibit better performance than their conventional counterpart due to the diminished piezoelectric polarization fields in QWs which can increase the density of electron and hole and the overlap of the electron and hole wavefunctions, and thus enhance the radiative recombination rate.
Numerical analysis on the effect of electron blocking layer in 365-nm ultraviolet light-emitting diodes
NASA Astrophysics Data System (ADS)
Chen, Fang-Ming; Chang, Jih-Yuan; Kuo, Yen-Kuang; Lin, Bing-Cheng; Kuo, Hao-Chung
For 365-nm ultraviolet light-emitting diodes (UV LEDs), an electron blocking layer (EBL) is usually utilized to mitigate electron overflow. However, using EBL might obstruct holes from injecting into the active region. Moreover, the large polarization field in conventional EBL might also pull down the effective barrier height for electrons, and thus the electrons could easily overflow to the p-side region. To solve the above drawbacks, in this study, the Al content and p-doping concentration of the EBL in typical 365-nm UV LEDs are investigated systematically. Specifically, designs of AlGaN/GaN superlattice EBL and Al-content-graded EBL are explored in detail.
Optical properties of nanopillar AlGaN/GaN MQWs for ultraviolet light-emitting diodes.
Dong, Peng; Yan, Jianchang; Zhang, Yun; Wang, Junxi; Geng, Chong; Zheng, Haiyang; Wei, Xuecheng; Yan, Qingfeng; Li, Jinmin
Nanopillar AlGaN/GaN multiple quantum wells ultraviolet light-emitting diodes (LEDs) were fabricated by nanosphere lithography and dry-etching. The optical properties of the nanopillar LEDs were characterized by both temperature-dependent and time-resolved photoluminescence measurements. Compared to an as-grown sample, the nanopillar sample has a PL emission peak blue-shift of 7 meV, a 42% enhanced internal quantum efficiency at room temperature and a reduced radiative recombination lifetime from 870 picosecond to 621 picosecond at 7K. These results are directly from the suppressed quantum confined stark effect that is due to the strain relaxation in the nanopillar MQWs, further revealed by micro-Raman measurement. Additionally, finite-difference time domain simulation also proves better light extraction efficiency in the nanopillar LEDs. PMID:24922241
Optical properties of nanopillar AlGaN/GaN MQWs for ultraviolet light-emitting diodes.
Dong, Peng; Yan, Jianchang; Zhang, Yun; Wang, Junxi; Geng, Chong; Zheng, Haiyang; Wei, Xuecheng; Yan, Qingfeng; Li, Jinmin
Nanopillar AlGaN/GaN multiple quantum wells ultraviolet light-emitting diodes (LEDs) were fabricated by nanosphere lithography and dry-etching. The optical properties of the nanopillar LEDs were characterized by both temperature-dependent and time-resolved photoluminescence measurements. Compared to an as-grown sample, the nanopillar sample has a PL emission peak blue-shift of 7 meV, a 42% enhanced internal quantum efficiency at room temperature and a reduced radiative recombination lifetime from 870 picosecond to 621 picosecond at 7K. These results are directly from the suppressed quantum confined stark effect that is due to the strain relaxation in the nanopillar MQWs, further revealed by micro-Raman measurement. Additionally, finite-difference time domain simulation also proves better light extraction efficiency in the nanopillar LEDs. PMID:24800288
Monolithically integrated III-Sb diode lasers on Si using interfacial misfit arrays
NASA Astrophysics Data System (ADS)
Huffaker, D. L.; Balakrishnan, G.; Jallipalli, A.; Kutty, M. N.; Huang, S. H.; Dawson, L. R.
We present a 1.54 ?m, 77 K, pulsed GaSb quantum well (QW) laser diode grown monolithically on a Si(100)-5░ substrate. The III-Sb device is grown on an AlSb nucleation layer on Si with the 13% mismatch accommodated by a self-assembled 2D array of pure 90░ dislocations. We demonstrate the simultaneous formation of this interfacial misfit dislocation (IMF) array along with antiphase domain suppression in the growth of AlSb on 5░ miscut Si (001) substrate. The lomer dislocation spacing in the IMF (~ 3.46 nm) corresponds to the 13% mismatch between AlSb and Si and is also well matched to the step length of the 5░ miscut Si (001) substrate. The resulting bulk material has both very low defect density (~7 ū 105/cm2) and very low APD density (~ 103/cm2) confirmed by transmission electron and atomic force microscope images. The GaSb QW based laser diodes are grown on this high quality AlSb layer and the resulting devices operate at 77 K under pulsed conditions (2 ?sec pulse-width and a 0.1% duty cycle) with an emission wavelength of 1.54 ?m and a threshold current density of 2 kA/cm2 for a 100 ?m x 2mm device. The maximum peak power from the device is ~ 20 mWatts.
Calibration and linearity verification of capacitance type cryo level indicators using cryogenically multiplexed diode array
NASA Astrophysics Data System (ADS)
Karunanithi, R.; Jacob, Subhash; Singh Gour, Abhay Singh; Das, M.; Nadig, D. S.; Prasad, M. V. N.
In space application the precision level measurement of cryogenic liquids in the storage tanks is done using triple redundant capacitance level sensor, for control and safety point of view. The linearity of each sensor element depends upon the cylindricity and concentricity of the internal and external electrodes. The complexity of calibrating all sensors together has been addressed by two step calibration methodology which has been developed and used for the calibration of six capacitance sensors. All calibrations are done using Liquid Nitrogen (LN2) as a cryogenic fluid. In the first step of calibration, one of the elements of Liquid Hydrogen (LH2) level sensor is calibrated using 700mm eleven point discrete diode array. Four wire method has been used for the diode array. Thus a linearity curve for a single element of LH2 is obtained. In second step of calibration, using the equation thus obtained for the above sensor, it is considered as a reference for calibrating remaining elements of the same LH2 sensor and other level sensor (either Liquid Oxygen (LOX) or LH2). The elimination of stray capacitance for the capacitance level probes has been attempted. The automatic data logging of capacitance values through GPIB is done using LabVIEW 8.5.
Comparison of continuous versus pulsed ultraviolet light emitting diode use for the inactivation of Bacillus globigii spores.
Tran, Tho; Racz, LeeAnn; Grimaila, Michael R; Miller, Michael; Harper, Willie F
Light emitting diodes (LEDs) in the ultraviolet (UV) range offer a promising alternative for the disinfection of water. LEDs have many advantages over conventional UV lamps but there are concerns related to the operating life of the LED lamps. In this project Bacillus globigii was inactivated using UV LED technology. The experimental strategy included using pulsed ultraviolet (PUV) output rather than continuous UV (CUV) current in order to reduce the power requirements and extend the life of the lamps. The kinetic profiles for CUV experiments reached 6-log inactivation faster than PUV at 9.1% duty cycle (approx. 840 vs. 5,000 s) but the PUV required lower fluence (365 vs. 665 J/m▓). In addition, the inactivation rate constants associated with PUV were generally higher than those of CUV (4.6-5.1 vs. 3.6-4.4 m▓/J), which supports the notion that high energy bursts are more effective at causing cellular damage. Multi-target kinetics applied to most of the kinetic observations and tailing effects were generally observed. PUV LED appears to have potential to extend the lifetime of the LEDs for inactivation of spore-forming pathogens. PMID:25401310
Evaluating dosimetric accuracy of flattening filter free compensator-based IMRT: Measurements with diode arrays
Robinson, Joshua; Opp, Daniel; Zhang, Geoffrey; Cashon, Ken; Kozelka, Jakub; Hunt, Dylan; Walker, Luke; Hoffe, Sarah; Shridhar, Ravi; Feygelman, Vladimir [Department of Physics, University of South Florida, Tampa, Florida 33612 (United States); Division of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States); decimal Inc., Sanford, Florida 32771 (United States); Sun Nuclear Corp., Melbourne, Florida 32940 (United States); Division of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States)
Purpose: Compensator-based IMRT coupled with the high dose rate flattening filter free (FFF) beams offers an intriguing possibility of delivering an intensity modulated radiation field in just a few seconds. As a first step, the authors evaluate the dosimetric accuracy of the treatment planning system (TPS) FFF beam model with compensators. Methods: A 6 MV FFF beam from a TrueBeam accelerator (Varian Medical Systems, Palo Alto CA) was modeled in PINNACLE TPS (v. 9.0, Philips Radiation Oncology, Fitchburg WI). Flat brass slabs from 0.3 to 7 cm thick and an 18 deg. brass wedge were used to adjust the beam model. A 2D (MAPCHECK) and 3D (ARCCHECK) diode arrays (Sun Nuclear Corp, Melbourne FL), were investigated for use with the compensator FFF beams. Corrections for diode sensitivity caused by the spectral changes in the beam were introduced. Four compensator plans based on the AAPM TG-119 report were developed. A composite ion chamber measurement, beam by beam MAPCHECK measurements, and a composite ARCCHECK measurement were performed. The array results were analyzed with the same thresholds as in TG-119 report--3%/3 mm with global dose normalization--as well as with the more stringent combinations of the gamma analysis criteria. Results: The FFF beam shows a greater variation of the effective attenuation coefficient with brass thickness due to the prevalence of the low energy photons compared to the conventional 6X beam. As a result, a compromise had to be made while trying to achieve dose agreement for a combination of field sizes, brass thicknesses, and measurement depths ({>=}5 cm in water). An agreement of measured and calculated dose to within 1% was observed for brass thicknesses up to 2 cm. For the 3 cm slab, an error of up to 2.8% was noted for the field sizes above 10 x 10 cm{sup 2}, and up to 3.8% for the 5 x 5 cm{sup 2} field. Both diode arrays exhibit a substantial sensitivity drop as the compensator thickness increases, reaching 10% for a 7 cm brass slab. A simple correction based on the brass thickness along the ray was introduced to counteract this effect. Pooled for five profiles, the average ratio of uncorrected and corrected MAPCHECK to ion chamber readings are 0.966 and 1.008, respectively. With the proper correction, all MAPCHECK measurement to calculation comparisons exhibit 100%{gamma}(3%/3 mm) passing rates with global dose-error normalization. For the TG-119-type plans, the average {gamma}(2%/2 mm) passing rate with local normalization is 94% (range 87.8%-98.3%). The lower ARCCHECK{gamma}-analysis passing rates (corrected for diode sensitivity) are predictable based on the observed PDD discrepancies. However, with the 3%/3 mm thresholds and global normalization, the average {gamma}-analysis passing rate is 96.4% (range 89.9%-100%). Conclusions: MAPCHECK analysis demonstrates high passing rates with the stringent {gamma}(2%/2 mm) and local normalization criteria combination. The geometry of the ARCCHECK array creates a stress test for the FFF TPS model because of the shallow depth of the entrance diodes and large air cavity. Hence, the ARCCHECK{gamma}-analysis passing rates are lower than with the MAPCHECK, while still on par with TG-119.
Enhanced photon extraction efficiency in 260nm pseudomorphic AlN-based ultraviolet light emitting diodes
Jamey R. Grandusky; Mark C. Mendrick; Shawn Gibb; Yong-Sung Kim; Shawn-Yu Lin; Leo J. Schowalter
Light sources in the wavelength range below 300nm have attracted extensive attention due to their applications in instrumentation and in disinfection of water, air and surface. Nitride-semiconductor-based, light emitting diodes (LEDs) are of especially great interest due to numerous advantages compared to conventional mercury lamps. Although significant progress of more than 9mW of quasi-CW power around 260nm at room temperature
A 10 ū 10 Gb/s DFB laser diode array fabricated using a SAG technique.
Kwon, Oh Kee; Leem, Yong Ahn; Han, Young Tak; Lee, Chul Wook; Kim, Ki Soo; Oh, Su Hwan
We present a ten-channel distributed feedback laser diode array (DFB-LDA) developed for the transmission of 100-Gb/s (10 ū 10 Gb/s) signals separated by an 8 nm wavelength grid at a center wavelength of 1.55 ?m. For the fabrication of this type of laser array, a selective area growth (SAG) technique, electron-beam lithography, and a reverse-mesa ridge waveguide LD processing technique were adopted to offer a tailored gain spectrum to each channel, providing both accurate lasing-wavelength control and excellent single-mode yield over all channels, and reducing the fabrication cost and electrical and thermal resistances. To evaluate the operational performance of the fabricated chip systematically, we also developed a sub-assembly module containing a ten-channel ?/4-shifted DFB-LDA, ten matching resistors, flexible printed circuit board (FPCB) wiring, and a thermistor on a metal optical bench. The static and dynamic properties of all channels of the fabricated array are examined in this paper. The developed sub-assembly module shows a side-mode suppression ratio (SMSR) of > 50 dB, a modulation bandwidth of > 10 GHz, and a clear eye-opening before and after a 2-km transmission with dynamic extinction ratio of > 5 dB. PMID:24787795
Coal liquefaction process streams characterization and evaluation: High performance liquid chromatography (HPLC) of coal liquefaction process streams using normal-phase separation with uv diode array detection
Clifford, D.J.; McKinney, D.E.; Hou, Lei; Hatcher, P.G. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering
This study demonstrated the considerable potential of using two-dimensional, high performance liquid chromatography (HPLC) with normal-phase separation and ultraviolet (UV) diode array detection for the examination of filtered process liquids and the 850{degrees}F{sup {minus}} distillate materials derived from direct coal liquefaction process streams. A commercially available HPLC column (Hypersil Green PAH-2) provided excellent separation of the complex mixture of polynuclear aromatic hydrocarbons (PAHs) found in coal-derived process streams process. Some characteristics of the samples delineated by separation could be attributed to processing parameters. Mass recovery of the process derived samples was low (5--50 wt %). Penn State believes, however, that, improved recovery can be achieved. High resolution mass spectrometry and gas chromatography/mass spectrometry (GC/MS) also were used in this study to characterize the samples and the HPLC fractions. The GC/MS technique was used to preliminarily examine the GC-elutable portion of the samples. The GC/MS data were compared with the data from the HPLC technique. The use of an ultraviolet detector in the HPLC work precludes detecting the aliphatic portion of the sample. The GC/MS allowed for identification and quantification of that portion of the samples. Further development of the 2-D HPLC analytical method as a process development tool appears justified based on the results of this project.
Quasi-diffraction limited emission from an array of tapered laser diodes in volume Bragg grating external cavities
Paris-Sud XI, Universit├® de
of a short ridge single-mode section, a 2.3 mm-long narrow-angle tapered ridge and a common amplified free induce a coherence between the individual emitters of the array and result in a brightness improvement [2 index-guided tapered laser diodes emitting around 975 nm. The lateral structure of the emitters consists
Handheld probe integrating laser diode and ultrasound transducer array for ultrasound/photoacoustic dual modality imaging.
Daoudi, K; van den Berg, P J; Rabot, O; Kohl, A; Tisserand, S; Brands, P; Steenbergen, W
Ultrasound and photoacoustics can be utilized as complementary imaging techniques to improve clinical diagnoses. Photoacoustics provides optical contrast and functional information while ultrasound provides structural and anatomical information. As of yet, photoacoustic imaging uses large and expensive systems, which limits their clinical application and makes the combination costly and impracticable. In this work we present and evaluate a compact and ergonomically designed handheld probe, connected to a portable ultrasound system for inexpensive, real-time dual-modality ultrasound/photoacoustic imaging. The probe integrates an ultrasound transducer array and a highly efficient diode stack laser emitting 130 ns pulses at 805 nm wavelength and a pulse energy of 0.56 mJ, with a high pulse repetition frequency of up to 10 kHz. The diodes are driven by a customized laser driver, which can be triggered externally with a high temporal stability necessary to synchronize the ultrasound detection and laser pulsing. The emitted beam is collimated with cylindrical micro-lenses and shaped using a diffractive optical element, delivering a homogenized rectangular light intensity distribution. The system performance was tested in vitro and in vivo by imaging a human finger joint. PMID:25401669
Spectral linewidth narrowing and tunable two-color laser operation of two diode laser arrays.
Liu, Bo; Braiman, Yehuda
We propose and implement a common external cavity to narrow spectral linewidth of two broad-area laser diode arrays (LDAs) and align their center wavelengths. The locked center wavelength of two LDAs can be tuned in the range of ~10 nm by tuning the tilted angle of the diffraction grating. The output beams of two LDAs are spatially overlapped through the polarization beam splitter of the common external cavity, and the total output power equals the power of two LDAs. The center wavelength of each LDA can be independently tuned by shifting the corresponding fast-axis collimation lens. As a result, the high-power two-color LDA operation is demonstrated with the tunable wavelength difference of up to 2 nm (~1 THz). PMID:22505175
Spectral Linewidth Narrowing and Tunable Two-Color Laser Operation of Two Diode Laser Arrays
Liu, Bo [ORNL; Braiman, Yehuda [ORNL
We propose and implement a common external cavity to narrow spectral linewidth of two broad-area laser diode arrays (LDAs) and align their center wavelengths. The locked center wavelength of two LDAs can be tuned in the range of {approx}10 nm by tuning the tilted angle of the diffraction grating. The output beams of two LDAs are spatially overlapped through the polarization beam splitter of the common external cavity, and the total output power equals the power of two LDAs. The center wavelength of each LDA can be independently tuned by shifting the corresponding fast-axis collimation lens. As a result, the high-power two-color LDA operation is demonstrated with the tunable wavelength difference of up to 2 nm ({approx}1 THz).
Intense Ultraviolet Electroluminescence Properties of the High-Power InGaN-Based Light-Emitting Diodes Fabricated on Patterned Sapphire Substrates
Hiromitsu Kudo; Kenji Murakami; Ruisheng Zheng; Yoichi Yamada; Tsunemasa Taguchi; Kazuyuki Tadatomo; Hiroaki Okagawa; Youichiro Ohuchi; Takashi Tsunekawa; Yoshiyuki Imada; Munehiro Kato
The electroluminescence and photoluminescence characteristics of high-efficient InGaN multi-quantum-well ultraviolet light-emitting diodes have been investigated. There appeared a single emission band in the electroluminescence spectra at about 3.235 eV with a band width of 90 meV at room temperature under direct current. With increasing forward current, the luminescence intensity was not saturated, and increased linearly with increasing injection current up
Efficient compact watt-level deep-ultraviolet laser generated from a multi-kHz Q-switched diode-pumped solid-state laser system
L. B. Chang; S. C. Wang; A. H. Kung
Stable high-power operation in the deep ultraviolet is achieved from a multi-kHz diode-pumped multi-longitudinal-mode Q-switched Nd:YAG laser by fourth harmonic generation in an external resonant cavity and by fifth harmonic generation using sum-frequency mixing of the fourth harmonic and the residual fundamental in a beta-BBO crystal. Over 2.1 W of 266 nm radiation and 540 mW of 213 nm radiation
Efficient compact watt-level deep-ultraviolet laser generated from a multi-kHz Q-switched diode-pumped solid-state laser system
L. B. Chang; S. C. Wang; A. H. Kung
Stable high-power operation in the deep ultraviolet is achieved from a multi-kHz diode-pumped multi-longitudinal-mode Q-switched Nd:YAG laser by fourth harmonic generation in an external resonant cavity and by fifth harmonic generation using sum-frequency mixing of the fourth harmonic and the residual fundamental in a ?-BBO crystal. Over 2.1 W of 266 nm radiation and 540 mW of 213 nm radiation
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: AlGaN-Based Deep-Ultraviolet Light Emitting Diodes Fabricated on AlN\\/sapphire Template
Li-Wen Sang; Zhi-Xin Qin; Hao Fang; Yan-Zhao Zhang; Tao Li; Zheng-Yu Xu; Zhi-Jian Yang; Bo Shen; Guo-Yi Zhang; Shu-Ping Li; Wei-Huang Yang; Hang-Yang Chen; Da-Yi Liu; Jun-Yong Kang
We report on the growth and fabrication of deep ultraviolet (DUV) light emitting diodes (LEDs) on an AlN template which was grown on a pulsed atomic-layer epitaxial buffer layer. Threading dislocation densities in the AlN layer are greatly decreased with the introduction of this buffer layer. The crystalline quality of the AlGaN epilayer is further improved by using a low-temperature
Large-area anodized alumina nanopore arrays assisted by soft ultraviolet nanoimprint prepatterning.
Ng, S M; Wong, H F; Lau, H K; Leung, C W
Aluminium anodization under optimized conditions can naturally generate close-packed and aligned nanopore arrays, but the spatial extent of such regular pore arrangement is generally limited. Here we demonstrated the use of soft ultraviolet nanoimprint lithography to guide the formation of nanopores at specific locations, using an elastomer negative mold for the process. By anodizing at voltages which naturally led to the formation of pores with matching averaged interpore separation, pre-patterned triangular holes (diameter 100 nm, periodicity 350 nm) on aluminium thin films induced conformal growth of nanopores at pre-defined positions. In addition, pores in geometries other than close-packed patterns were prepared, with square pore arrangement being demonstrated in this work. The influence of the anodization voltage on the final pore formation was also studied. Our results illustrated the possibility to fabricate well-organized nanopore arrays with conditions far less stringent than those reported in literature, which has the potential to be adopted for applications where regular pore alignment are critical. PMID:22962742
Growth of ZnO Nanowire Arrays for Advanced Ultraviolet Detectors
NASA Astrophysics Data System (ADS)
Zeller, John; Manzur, Tariq; Anwar, A. F. Mehdi; Sood, Ashok K.
Zinc oxide (ZnO) provides a unique wide bandgap biocompatible material system exhibiting both semiconducting and piezoelectric properties. Bulk ZnO has a bandgap of 3.37 eV that corresponds to emissions in the solar blind ultraviolet (UV) spectral band (240-280 nm). We have grown highly ordered vertical arrays of ZnO nanowires using the metal organic chemical vapor deposition (MOCVD) technique on Si, silicon dioxide, c-plane sapphire, and GaN epitaxial substrates. UV detectors based on ZnO nanowires offer the highest UV sensitivity and lowest visible sensitivity for applications such as missile plume detection and threat warning. The development of UV detectors based on vertical nanowire arrays requires an innovative fabrication approach involving precise deposition of metal contacts, where UV sensor performance depends to a large extent on the growth conditions as well as on the substrate used. We will present experimental results on the structural, electrical, and optical properties of ZnO nanowires grown for UV sensing applications.
Fast single-photon avalanche diode arrays for laser Raman spectroscopy.
Blacksberg, Jordana; Maruyama, Yuki; Charbon, Edoardo; Rossman, George R
We incorporate newly developed solid-state detector technology into time-resolved laser Raman spectroscopy, demonstrating the ability to distinguish spectra from Raman and fluorescence processes. As a proof of concept, we show fluorescence rejection on highly fluorescent mineral samples willemite and spodumene using a 128ū128 single-photon avalanche diode (SPAD) array with a measured photon detection efficiency of 5%. The sensitivity achieved in this new instrument architecture is comparable to the sensitivity of a technically more complicated system using a traditional photocathode-based imager. By increasing the SPAD active area and improving coupling efficiency, we expect further improvements in sensitivity by over an order of magnitude. We discuss the relevance of these results to in situ planetary instruments, where size, weight, power, and radiation hardness are of prime concern. The potential large-scale manufacturability of silicon SPAD arrays makes them prime candidates for future portable and in situ Raman instruments spanning numerous applications where fluorescence interference is problematic. PMID:21931428
Fabrication of Organic Light-Emitting Diode Arrays on Flexible Plastic Substrates by Imprint Lithography
NASA Astrophysics Data System (ADS)
Cheng, Chiao-Yang; Hong, Franklin Chau-Nan
Imprint lithography has been employed as a patterning technology for the fabrication of organic light-emitting diode (OLED) device arrays on flexible poly(ethylene terephthalate) (PET) substrates. Poly(methyl methacrylate) (PMMA) was used as the etching barrier coated on an indium tin oxide (ITO)/PET substrate. A silicon mold fabricated by photolithography was coated with a fluorinated diamond-like carbon film for easy mold-releasing. By hot pressing the silicon mold on the PMMA-coated ITO/PET substrate and etching in oxalic acid solution, patterned ITO strips were obtained. Imprint lithography was repeated to fabricate PMMA ribs vertical to the ITO strips. Finally, a matrix of 40ū 40 OLED devices (300ū 300 ?m2) was fabricated with an area of 25ū 25 mm2 after depositing the organic and cathode layers consisting of TPD/Alq3/Bphen/LiF/Al. High quality OLED arrays on flexible PET substrate were obtained with a turn-on voltage of around 5 V, a luminous efficiency of 3 cd/A, a power efficiency of 1.2 lm/W, and a luminance of 800 cd/m2 operated at 7 V on the basis of the actual light emitting area.
Semiconducting polymer diodes: Large size, low cost photodetectors with excellent visible-ultraviolet sensitivity
Yu, G.; Pakbaz, K.; Heeger, A.J. (Institute for Polymers and Organic Solids, University of California at Santa Barbara, Santa Barbara, California 93106-5090 (United States))
Photodiodes fabricated from conjugated polymers exhibit excellent sensitivity to visible-UV radiation. The photosensitivity increases with reverse bias voltage. The photoresponse of diodes fabricated from poly(3-octyl thiophene) is relatively flat in the visible and near UV; for wavelengths shorter than 550 nm, the absolute sensitivity is greater than 0.3 A/W under reverse bias of 15 V, larger than that of commercial UV-enhanced Si photodiodes. Photodiodes made from poly[2-methoxy-5-(2[prime]-ethyl-hexyloxy)-1,4-phenylene vinylene], MEH-PPV, sensitized with C[sub 60], show similar sensitivity. The ease of fabrication into large size, arbitrary shapes, and even onto flexible substrates makes the polymer photodiode a novel photodetector with potential for use in a wide range of applications.
Nanosecond time-resolved vacuum ultraviolet spectrometer for ion diode spectroscopy
NASA Astrophysics Data System (ADS)
Nash, T.; Noack, D.; Filuk, A. B.
A 1-m normal incidence spectrometer has been modified for use as a diagnostic of ion diode plasmas. To improve instrumental sensitivity, an elliptical mirror images an anode surface plasma onto the entrance slit of an f/10 normal incidence spectrometer. The detector is a time-resolving copper iodide coated microchannel plate stripline framing camera with 60-?m resolution, limiting instrumental resolution to 1 ┼ with a 600 l/mm grating in first order. Reflectivity of optics and photoelectron efficiency limit the spectral range from 400 to 2000 ┼. With a 600-l/mm grating the detector spans a 600-┼ range. Applications of the instrument may include ion source divergence measurements from Doppler broadening, electric field measurements from Stark splittings or shifts, electron temperature from mean ionization state, and magnetic field measurements on high-power Z pinches from Zeeman splitting.
High Power Efficiency AlGaN-Based Ultraviolet Light-Emitting Diodes
NASA Astrophysics Data System (ADS)
Passow, Thorsten; Gutt, Richard; Kunzer, Michael; Pletschen, Wilfried; Kirste, Lutz; Forghani, Kamran; Scholz, Ferdinand; K÷hler, Klaus; Wagner, Joachim
High-efficiency AlGaN-based 355 nm UV light-emitting diodes (LEDs) grown on low-dislocation-density AlGaN/sapphire templates with an output power of 9.8 mW (22.7 mW) at a DC current of 40 mA (100 mA) are reported. The corresponding maximum external quantum efficiency and maximum power efficiency are 7.2 and 6.5%, respectively. Based on a rate equation model, a method is presented to derive the extraction as well as the injection and internal quantum efficiency as a function of the driving current. The thus obtained injection and internal quantum efficiencies amount to 51 and 47% at 40 mA, the extraction efficiency to 29%.
Ultraviolet-enhanced light emitting diode employing individual ZnO microwire with SiO2 barrier layers
NASA Astrophysics Data System (ADS)
Xu, Yingtian; Xu, Li; Dai, Jun; Ma, Yan; Chu, Xianwei; Zhang, Yuantao; Du, Guotong; Zhang, Baolin; Yin, Jingzhi
This paper details the fabrication of n-ZnO single microwire (SMW)-based high-purity ultraviolet light-emitting diodes (UV-LEDs) with an added SiO2 barrier layer on the p-Si substrate. However, the current-voltage (I-V) curve exhibited non-ideal rectifying characteristics. Under forward bias, both UV and visible emissions could be detected by electroluminescence (EL) measurement. When bias voltage reached 60 V at room temperature, a UV emission spike occurred at 390 nm originating from the n-ZnO SMW. Compared with the EL spectrum of the n-ZnO SMW/p-Si heterojunction device without the SiO2 barrier layer, we saw improved UV light extraction efficiency from the current-blocking effect of the SiO2 layer. The intense UV emission in the n-ZnO SMW/SiO2/p-Si heterojunction indicated that the SiO2 barrier layer can restrict the movement of electrons as expected and result in effective electron-hole recombination in ZnO SMW.
High quantum efficiency for Pt2Si Schottky-barrier diodes in the vacuum ultraviolet
NASA Astrophysics Data System (ADS)
Hajsaid, M.; Charlson, E. J.; Charlson, E. M.; Zhao, G.; Meese, J. M.; Stacy, T.; Popovici, G.; Prelas, M. A.
In the current study an effort was made to extend the front-illumination mode experiments into the 100-200 nm vacuum ultraviolet range. It was found that devices that were configured to form the Pt2Si phase, always displayed higher efficiencies in the VUV. Fabrication of the Pt2Si morphology was mainly determined by the annealing temperature. Thus, the formation and measurement of this variety of the device were stressed. The quantum efficiency measurements of the two sets of Pt2Si photodiodes were obtained by using the difference in short-circuit photocurrent of the device currents with and without illumination. Two major factors influenced the detector response, namely, substrate resistivity and thickness of the silicide film. The results showed that there was a maximum thickness of the silicide film for maximal photoresponse in the VUV wavelength range.
Wearable red¢green¢blue quantum dot light-emitting diode array using high-resolution intaglio transfer printing
Choi, Moon Kee; Yang, Jiwoong; Kang, Kwanghun; Kim, Dong Chan; Choi, Changsoon; Park, Chaneui; Kim, Seok Joo; Chae, Sue In; Kim, Tae-Ho; Kim, Ji Hoon; Hyeon, Taeghwan; Kim, Dae-Hyeong
Deformable full-colour light-emitting diodes with ultrafine pixels are essential for wearable electronics, which requires the conformal integration on curvilinear surface as well as retina-like high-definition displays. However, there are remaining challenges in terms of polychromatic configuration, electroluminescence efficiency and/or multidirectional deformability. Here we present ultra-thin, wearable colloidal quantum dot light-emitting diode arrays utilizing the intaglio transfer printing technique, which allows the alignment of red¢green¢blue pixels with high resolutions up to 2,460 pixels per inch. This technique is readily scalable and adaptable for low-voltage-driven pixelated white quantum dot light-emitting diodes and electronic tattoos, showing the best electroluminescence performance (14,000?cd?m?2 at 7?V) among the wearable light-emitting diodes reported up to date. The device performance is stable on flat, curved and convoluted surfaces under mechanical deformations such as bending, crumpling and wrinkling. These deformable device arrays highlight new possibilities for integrating high-definition full-colour displays in wearable electronics. PMID:25971194
Wearable red-green-blue quantum dot light-emitting diode array using high-resolution intaglio transfer printing.
Choi, Moon Kee; Yang, Jiwoong; Kang, Kwanghun; Kim, Dong Chan; Choi, Changsoon; Park, Chaneui; Kim, Seok Joo; Chae, Sue In; Kim, Tae-Ho; Kim, Ji Hoon; Hyeon, Taeghwan; Kim, Dae-Hyeong
Deformable full-colour light-emitting diodes with ultrafine pixels are essential for wearable electronics, which requires the conformal integration on curvilinear surface as well as retina-like high-definition displays. However, there are remaining challenges in terms of polychromatic configuration, electroluminescence efficiency and/or multidirectional deformability. Here we present ultra-thin, wearable colloidal quantum dot light-emitting diode arrays utilizing the intaglio transfer printing technique, which allows the alignment of red-green-blue pixels with high resolutions up to 2,460 pixels per inch. This technique is readily scalable and adaptable for low-voltage-driven pixelated white quantum dot light-emitting diodes and electronic tattoos, showing the best electroluminescence performance (14,000?cd?m(-2) at 7?V) among the wearable light-emitting diodes reported up to date. The device performance is stable on flat, curved and convoluted surfaces under mechanical deformations such as bending, crumpling and wrinkling. These deformable device arrays highlight new possibilities for integrating high-definition full-colour displays in wearable electronics. PMID:25971194
Sampling and identification of natural dyes in historical maps and drawings by liquid chromatography with diode-array detection
Rosario Blanc; Teresa Espejo; Ana L¾pez-Montes; David Torres; Guillermo Crovetto; Alberto Naval¾n; Josķ Luis VĒlchez
A simple and rapid liquid chromatographic with diode-array UV¢vis spectrophotometric detection (HPLC¢DAD) method for identification of natural dyes has been developed. Chromatographic retention of carminic acid, indigotin, crocetin, gambogic acid, alizarin and purpurin has been studied. The mobile phase consisted of 40mM SDS¢10mM phosphate buffer solution (pH 2.3)¢0.1% TFA (eluent A) and acetonitrile (eluent B) using a programmed gradient (5%
1.471.49-m InGaAsPInP diode laser arrays A. Gourevitch,a)
characteristics of 1.47Ł1.49- m one-dimensional 1D and two-dimensional 2D InP-based diode laser arrays designed and analytically investigated. The InGaAsP/InP heterostructures were grown by orga- nometallic chemical vapor. This arrangement removes heat from both sides of the laser bar. Figure 1 shows the current dependencies of the cw
Injection-locking characteristics of gain-guided diode laser arrays with an on-chip'' master laser
Hohimer, J.P.; Myers, D.R.; Brennan, T.M.; Hammons, B.E. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (USA))
We report measurements of the injection-locking characteristics of a high-power continuous-wave diode laser array with an on-chip independently controlled master laser. This integrated injection-locked array emits a near-diffraction-limited single-lobed output beam at cw power levels up to 220 mW/facet. By controlling the current to the master laser, the single-lobed output beam can be electronically steered over a far-field angle of {gt}1.7{degree}. We also report preliminary studies of the coupling interaction in these integrated devices.
Monolithic two-dimensional surface-emitting arrays of GaAs/AlGaAs diode lasers
NASA Technical Reports Server (NTRS)
Monolithic two-dimensional arrays of GaAs/AlGaAs diode lasers with light emission normal to the surface have been obtained by fabricating edge-emitting quantum-well lasers coupled with external mirrors that deflect the radiation from the laser facets by 90 degrees. Linear arrays of GaAs/AlGaAs devices in which one of the laser facets was cleaved while the other facet and an adjacent 45 degree deflector were formed by ion-beam-assisted etching (IBAE) have been reported. For the arrays reported in this section, IBAE was used to form all of the laser facets and the deflecting mirrors. A mass transport process of the type employed to fabricate two-dimensional arrays of GaInAsP/InP lasers coupled with deflecting mirrors is not known for AlGaAs.
Abstract Exposure to ultraviolet-B radiation (UV-B; 280320 nm) has a wide array of effects on aquatic or-
Blaustein, Andrew R.
Abstract Exposure to ultraviolet-B radiation (UV-B; 280Ł320 nm) has a wide array of effects of embryos to ambient UV-B radiation would result in sub- lethal effects on larval growth and development. We. Keywords Amphibians Ę Rana aurora Ę Sublethal effects Ę Ultraviolet radiation Ę UV-B Introduction
Improve beam quality of high-power laser diode array stacks by external-cavity technique
NASA Astrophysics Data System (ADS)
Pi, Haoyang; Xin, Guofeng; Qu, Ronghui; Fang, Zujie
Because of its own structure's limitation, the beam divergence angle of the semiconductor laser is very large. In the fastaxis direction, the beam plays good quality and can be collimated less than 1░ by using cylindrical micro-lens. However, in the slow-axis direction, the beam quality is too poor to be collimated to a small pattern. This could limit its application in the fields which need high beam quality. For high-power laser diode array (LDA), external-cavity technique can make all the emitters working in the same wavelength, and can improve their beam quality. In this paper, direct feedback method was employed to achieve cross-injection between 25 emitters of a LD bar by using a stripe mirror. At a certain cavity length, after the reflection of the external-cavity mirror's reflective stripe, the beam with large slow-axis divergence angle will feedback to the spacer region between the emitters and lose its energy, or would exactly feedback to the neighbor emitter. Simultaneously, the beam with small divergence angle would output from the transparent stripe of the external-cavity mirror. The slow-axis divergence of the stacks with two bars was suppressed from 6░to 2░by using this technique.
Validated HPLC-Diode Array Detector Method for Simultaneous Evaluation of Six Quality Markers in Coffee.
Gant, Anastasia; Leyva, Vanessa E; Gonzalez, Ana E; Maruenda, Helena
Nicotinic acid, N-methylpyridinium ion, and trigonelline are well studied nutritional biomarkers present in coffee, and they are indicators of thermal decomposition during roasting. However, no method is yet available for their simultaneous determination. This paper describes a rapid and validated HPLC-diode array detector method for the simultaneous quantitation of caffeine, trigonelline, nicotinic acid, N-methylpyridinium ion, 5-caffeoylquinic acid, and 5-hydroxymethyl furfural that is applicable to three coffee matrixes: green, roasted, and instant. Baseline separation among all compounds was achieved in 30 min using a phenyl-hexyl RP column (250 ū 4.6 mm, 5 ?m particle size), 0.3% aqueous formic buffer (pH 2.4)-methanol mobile phase at a flow rate of 1 mL/min, and a column temperature at 30░C. The method showed good linear correlation (r(2) > 0.9985), precision (less than 3.9%), sensitivity (LOD = 0.023-0.237 ?g/mL; LOQ = 0.069-0.711 ?g/mL), and recovery (84-102%) for all compounds. This simplified method is amenable for a more complete routine evaluation of coffee in industry. PMID:25857885
Instrumentation: Photodiode Array Detectors in UV-VIS Spectroscopy. Part II.
ERIC Educational Resources Information Center
Jones, Dianna G.
A previous part (Analytical Chemistry; v57 n9 p1057A) discussed the theoretical aspects of diode ultraviolet-visual (UV-VIS) spectroscopy. This part describes the applications of diode arrays in analytical chemistry, also considering spectroelectrochemistry, high performance liquid chromatography (HPLC), HPLC data processing, stopped flow, andģ
Application of GaN-based ultraviolet-C light emitting diodes--UV LEDs--for water disinfection.
W³rtele, M A; Kolbe, T; Lipsz, M; K³lberg, A; Weyers, M; Kneissl, M; Jekel, M
GaN-based ultraviolet-C (UV-C) light emitting diodes (LEDs) are of great interest for water disinfection. They offer significant advantages compared to conventional mercury lamps due to their compact form factor, low power requirements, high efficiency, non-toxicity, and overall robustness. However, despite the significant progress in the performance of semiconductor based UV LEDs that has been achieved in recent years, these devices still suffer from low emission power and relatively short lifetimes. Even the best UV LEDs exhibit external quantum efficiencies of only 1-2%. The objective of this study was to investigate the suitability of GaN-based UV LEDs for water disinfection. The investigation included the evaluation of the performance characteristics of UV LEDs at different operating conditions as well as the design of a UV LED module in view of the requirements for water treatment applications. Bioanalytical testing was conducted using Bacillus subtilis spores as test organism and UV LED modules with emission wavelengths of 269 nm and 282 nm. The results demonstrate the functionality of the developed UV LED disinfection modules. GaN-based UV LEDs effectively inactivated B. subtilis spores during static and flow-through tests applying varying water qualities. The 269 nm LEDs reached a higher level of inactivation than the 282 nm LEDs for the same applied fluence. The lower inactivation achieved by the 282 nm LEDs was compensated by their higher photon flux. First flow-through tests indicate a linear correlation between inactivation and fluence, demonstrating a well designed flow-through reactor. With improved light output and reduced costs, GaN-based UV LEDs can provide a promising alternative for decentralised and mobile water disinfection systems. PMID:21115187
Low-Temperature Growth of Well-Aligned ZnO Nanorod Arrays by Chemical Bath Deposition for Schottky Diode Application
NASA Astrophysics Data System (ADS)
Yuan, Zhaolin
A well-aligned ZnO nanorod array (ZNRA) was successfully grown on an indium tin oxide (ITO) substrate by chemical bath deposition at low temperature. The morphology, crystalline structure, transmittance spectrum and photoluminescence spectrum of as-grown ZNRA were investigated by field emission scanning electron microscopy, x-ray diffraction, ultraviolet-visible spectroscopy and spectrophotometer, respectively. The results of these measurements showed that the ZNRA contained densely packed, aligned nanorods with diameters from 30 nm to 40 nm and a wurtzite structure. The ZNRA exhibited good optical transparency within the visible spectral range, with >80% transmission. Gold (Au) was deposited on top of the ZNRA, and the current-voltage characteristics of the resulting ITO/ZNRA/Au device in the dark were evaluated in detail. The ITO/ZNRA/Au device acted as a Schottky barrier diode with rectifying behaviour, low turn-on voltage (0.6 V), small reverse-bias saturation current (3.73 ū 10-6 A), a high ideality factor (3.75), and a reasonable barrier height (0.65 V) between the ZNRA and Au.
Demonstration of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes on High-Quality AlN Templates
Yusuke Sakai; Youhua Zhu; Shigeaki Sumiya; Makoto Miyoshi; Mitsuhiro Tanaka; Takashi Egawa
The authors demonstrate AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) on high-quality AlN\\/sapphire template (AlN template) by evaluating its characteristics. LED structures can be grown directly on 2-in.-diameter AlN template by metal-organic chemical vapor deposition. AlGaN epilayers are confirmed to have high crystal quality on AlN template through X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM). The fabricated LEDs exhibit a
Characterization of a novel two dimensional diode array the ''magic plate'' as a radiation detector for radiation therapy treatment
Wong, J. H. D.; Fuduli, I.; Carolan, M.; Petasecca, M.; Lerch, M. L. F.; Perevertaylo, V. L.; Metcalfe, P.; Rosenfeld, A. B. [Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia and Faculty of Medicine, University of Malaya, Kuala Lumpur 50603 (Malaysia); Centre for Medical Radiation Physics, University of Wollongong, NSW 2522 (Australia); Illawarra Cancer Care Centre, Wollongong Hospital, NSW 2500, Australia and Centre for Medical Radiation Physics, University of Wollongong, NSW 2522 (Australia); Centre for Medical Radiation Physics, University of Wollongong, NSW 2522 (Australia); SPA BIT, Kiev, Ukraine, 04136 (Ukraine); Centre for Medical Radiation Physics, University of Wollongong, NSW 2522 (Australia)
Purpose: Intensity modulated radiation therapy (IMRT) utilizes the technology of multileaf collimators to deliver highly modulated and complex radiation treatment. Dosimetric verification of the IMRT treatment requires the verification of the delivered dose distribution. Two dimensional ion chamber or diode arrays are gaining popularity as a dosimeter of choice due to their real time feedback compared to film dosimetry. This paper describes the characterization of a novel 2D diode array, which has been named the ''magic plate'' (MP). It was designed to function as a 2D transmission detector as well as a planar detector for dose distribution measurements in a solid water phantom for the dosimetric verification of IMRT treatment delivery. Methods: The prototype MP is an 11 x 11 detector array based on thin (50 {mu}m) epitaxial diode technology mounted on a 0.6 mm thick Kapton substrate using a proprietary ''drop-in'' technology developed by the Centre for Medical Radiation Physics, University of Wollongong. A full characterization of the detector was performed, including radiation damage study, dose per pulse effect, percent depth dose comparison with CC13 ion chamber and build up characteristics with a parallel plane ion chamber measurements, dose linearity, energy response and angular response. Results: Postirradiated magic plate diodes showed a reproducibility of 2.1%. The MP dose per pulse response decreased at higher dose rates while at lower dose rates the MP appears to be dose rate independent. The depth dose measurement of the MP agrees with ion chamber depth dose measurements to within 0.7% while dose linearity was excellent. MP showed angular response dependency due to the anisotropy of the silicon diode with the maximum variation in angular response of 10.8% at gantry angle 180 deg. Angular dependence was within 3.5% for the gantry angles {+-} 75 deg. The field size dependence of the MP at isocenter agrees with ion chamber measurement to within 1.1%. In the beam perturbation study, the surface dose increased by 12.1% for a 30 x 30 cm{sup 2} field size at the source to detector distance (SDD) of 80 cm whilst the transmission for the MP was 99%. Conclusions: The radiation response of the magic plate was successfully characterized. The array of epitaxial silicon based detectors with ''drop-in'' packaging showed properties suitable to be used as a simplified multipurpose and nonperturbing 2D radiation detector for radiation therapy dosimetric verification.
Variable FOV optical illumination system with constant aspect ratio for 2-D array lasers diodes
NASA Astrophysics Data System (ADS)
Arasa, J.; de la Fuente, M. C.; Iba±ez, C.
In this contribution we present a compact system to create an illumination distribution with a constant aspect ratio 3:4 and FOV from 0.4 to 1 degree. Besides, the system must delivery 40 W from 170 individual laser diodes placed in a regular 2-D array distribution of 10 x 20 mm. The main problem that must be solved is the high asymmetry of the individual sources; emission divergence's ratio 3:73 (0.3 vs. 7.4 degree) combined with the flux holes due to the laser's heat drain. In one axis (divergence of 0.3┬║) the best design strategy approach is a Galileo telescope but in the other axis a collimator configuration is the best solution. To manage both solutions at the same time is the aim of this contribution. Unfortunately for the Galileo strategy, source dimensions are too large so aspheric surfaces are needed, and the collimator configuration requires an EFL that must change from 573 to 1432 mm. The presented solution uses a set of three fixed anamorphic lenses, two of them pure cylinders, combined with a wheel of anamorphic lenses that have the function to change the FOV of the system. The most important contribution of the design is to obtain a constant final ratio 3:4 from an initial ratio of 3:73 with no losses of energy. The proposed solution produces an illumination pattern with peaks and valleys lower than 40%. This pattern distribution might be unacceptable for a standard illumination solution. However, the actual FOV is used to illuminate far away targets thus air turbulence is enough to homogenize the distribution on the target.
Ultra-violet Sensing Characteristic and Field Emission Properties of Vertically Aligned Aluminum Doped Zinc Oxide Nanorod Arrays
Mamat, M. H.; Malek, M. F.; Musa, M. Z. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Khusaimi, Z. [NANO-SciTech Centre (NST), Institute of Science (IOS), Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia); Rusop, M. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia) and NANO-SciTech Centre (NST), Institute of Science (IOS), Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia)
Ultra-violet (UV) sensing behavior and field emission characteristic have been investigated on vertically aligned aluminum (Al) doped zinc oxide (ZnO) nanorod arrays prepared using sol-gel immersion method. Uniform and high coverage density of ZnO nanorod arrays have been successfully deposited on seeded-catalyst coated substrates. The synthesized nanorods have diameter sizes between 50 nm to 150 nm. The XRD spectra show Al doped ZnO nanorod array has high crystallinity properties with the dominancy of crystal growth along (002) plane or c-axis. UV photoresponse measurement indicates that Al doped ZnO nanorod array sensitively detects UV light as shown by conductance increment after UV illumination exposure. The nanorod array shows good field emission properties with low turn on field and threshold field at 2.1 V/{mu}m and 5.6 V/{mu}m, respectively. The result suggested that Al doped ZnO nanorod arrays prepared by low-cost sol-gel immersion method show promising result towards fabrication of multi applications especially in UV photoconductive sensor and field emission displays.
Tapered gain guides in diode lasers and picosecond Q- switched bow tie laser arrays
Daniel John Kitcher
The use of the tapered waveguide to simultaneously expand and amplify the output of a diode laser has recently led to an order-of-magnitude increase in the continuous power and the picosecond pulsed output that can be obtained from a diode laser in a single spatial mode. The theoretical and experimental investigation of gain- guiding has been used as a basis
High intensity light emitting diode array as an alternative exposure source for the fabrication of electrophoretic microfluidic devices.
Breadmore, Michael C; Guijt, Rosanne M
A commercially available array of light emitting diodes (LEDs), namely a UV Shark series LED high flux array, was evaluated as a light source for photolithographic patterning of SU-8 photoresist for the fabrication of templates suitable to make poly(dimethylsiloxane) (PDMS) microchips for electrophoresis. At a distance of 15 cm from the substrate, a relatively even intensity of 0.76+/-0.05 mW/cm(2) was obtained over an area sufficient for patterning a 10 cm (4 in.) silicon wafer. The exposure source was evaluated using a spiral mask design covering a 10 cm wafer. PDMS replicates of this template made in a 25 microm thick layer of SU-8 3025 showed little variation in width over the surface of the substrate, with a variation of 3.2% RSD (n=36) and a maximum range in widths of 7.8% of the mean channel width. The use of the optional metal reflector available with the LED array provided partial collimation of the light allowing near vertical structures to be produced across the entire wafer, something which was not possible without the reflector. SU-8 masters prepared using the LED array were compared to masters made using an alternative cheap lithographic source, namely a gel crosslinker. The SU-8 features were much narrower with the LED array than the crosslinker due to the multiple light sources in the crosslinker. A PDMS microchip made using a SU-8 template created using the Shark UV LED array was used for the electrophoretic separation of three anionic fluorescent dyes, with efficiencies up to 32,000 plates. Given that the LED array can be purchased and assembled for less than US$ 500, the Shark UV LED array is a promising alternative to more expensive lithographic light sources and will have significant appeal to many researchers wishing to undertake research in microfluidics around the world. PMID:18930463
Single-element optical injection locking of diode-laser arrays
Hadley, G. Ronald (Albuquerque, NM); Hohimer, John P. (Albuquerque, NM); Owyoung, Adelbert (Albuquerque, NM)
By optically injecting a single end-element of a semiconductor laser array, both the spatial and spectral emission characteristics of the entire laser array is controlled. With the output of the array locked, the far-field emission angle of the array is continuously scanned over several degrees by varying the injection frequency.
Toward single-molecule detection with very compact DNA sequencer based on single-photon avalanche diode array
NASA Astrophysics Data System (ADS)
Rech, Ivan; Marangoni, Stefano; Gulinatti, Angelo; Ghioni, Massimo; Cova, Sergio
The development of a very-compact DNA sequencer instrument based on Single Photon Avalanche Diode (SPAD) for microchip electrophoresis is here reported. The planar epitaxial SPAD combines the typical advantages of microelectronic devices with high sensitivity. We present a miniaturized system based on a custom array of SPAD, purposely designed to be compatible with Amersham Biosciences commercial markers. This system is the first example of very compact, ultra-sensitive, portable and low cost DNA sequencer. It may represent a breakthrough in DNA sequencing system and open the way to the development of a new category of portable low-cost apparatus.
High-purity hydrogen generation by ultraviolet illumination with the membrane composed of titanium dioxide nanotube array and Pd layer
NASA Astrophysics Data System (ADS)
Hattori, Masashi; Noda, Kei; Matsushige, Kazumi
High-purity hydrogen generation was observed by using a membrane composed of a bilayer of an anodized titanium dioxide nanotube array (TNA) and a hydrogen permeable metal. This membrane was fabricated by transferring a TNA embedded in a titanium foil onto a sputtered 10-?m-thick palladium film. Alcohols are reformed photocatalytically and concurrently generated hydrogen is purified through the Pd layer. H2 with a purity of more than 99% was obtained from liquid alcohols under ultraviolet illumination onto the membrane. Thus, we demonstrated the integration of photocatalytic hydrogen production and purification within a single membrane.
A Comparative Analysis for Verification of IMRT and VMAT Treatment Plans using a 2-D and 3-D Diode Array
NASA Astrophysics Data System (ADS)
Dance, Michael J.
With the added complexity of current radiation treatment dose delivery modalities such as IMRT (Intensity Modulated Radiation Therapy) and VMAT (Volumetric Modulated Arc Therapy), quality assurance (QA) of these plans become multifaceted and labor intensive. To simplify the patient specific quality assurance process, 2D or 3D diode arrays are used to measure the radiation fluence for IMRT and VMAT treatments which can then be quickly and easily compared against the planned dose distribution. Because the arrays that can be used for IMRT and VMAT patient-specific quality assurance are of different geometry (planar vs. cylindrical), the same IMRT or VMAT treatment plan measured by two different arrays could lead to different measured radiation fluences, regardless of the output and performance of linear accelerator. Thus, the purpose of this study is to compare patient specific QA results as measured by the MapCHECK 2 and ArcCHECK diode arrays for the same IMRT and VMAT treatment plans to see if one diode array consistently provides a closer comparison to reference data. Six prostate and three thoracic spine IMRT treatment plans as well as three prostate and three thoracic spine VMAT treatment plans were produced. Radiotherapy plans for this study were generated using the Pinnacle TPS v9.6 (Philips Radiation Oncology Systems, Fitchburg, WI) using 6 MV, 6 MV FFF, and 10 MV x-ray beams from a Varian TrueBeam linear accelerator (Varian Medical Systems, Palo Alto, CA) with a 120-millenium multi-leaf collimator (MLC). Each IMRT and VMAT therapy plan was measured on Sun Nuclear's MapCHECK 2 and ArcCHECK diode arrays. IMRT measured data was compared with planned dose distribution using Sun Nuclear's 3DVH quality assurance software program using gamma analysis and dose-volume histograms for target volumes and critical structures comparison. VMAT arc plans measured on the MapCHECK 2 and ArcCHECK were compared using beam-by-beam analysis with the gamma evaluation method with Sun Nuclear's SNC Patient (TM) analysis software. MapCHECK 2 showed a slightly better agreement with planned data for IMRT verifications with a mean pass rate of 99.4% for clinically used acceptance criteria of 3%/3mm. MapCHECK 2's 99.4% mean pass rate for IMRT verifications was 1.4% higher than ArcCHECK's mean pass rate. For VMAT verifications, the MapCHECK 2 had a mean pass rate of 99.6% and 100% for each arc respectively, resulting in a 1.25% to 1.92% higher mean passing rates than those measured by the ArcCHECK using an acceptance criteria of 3%/3mm. MapCHECK 2 showed consistently higher ROI-specific mean gamma passing rates, ranging from +0.2% to +5.6%. While neither diode array showed any advantage in regards to D95 measurements within the PTV, MapCHECK 2 again showed closer comparison data in the CTV/GTV with an absolute deviation of -1.14 Gy compared to -3.39 Gy as measured by the ArcCHECK. Lastly, while the MapCHECK 2 and ArcCHECK both closely matched with the reference doses within the PTV and CTV/GTV, the ArcCHECK consistently overestimated the maximum absolute dose to all ROI, from 0.026 Gy to 2.243 Gy. In conclusion, the MapCHECK 2 diode array measured data more closely matched with planned data compared to the ArcCHECK diode array for IMRT verifications. While MapCHECK 2 showed a marginally better gamma passing rates over the ArcCHECK diode array, the ArcCHECK's ability to simultaneously measure flatness, symmetry, output, and MLC positional accuracy as a function of gantry angle make it a more realistic and efficient measurement device for VMAT verifications.
Real-time brightfield, darkfield, and phase contrast imaging in a light-emitting diode array microscope.
Liu, Ziji; Tian, Lei; Liu, Sijia; Waller, Laura
We demonstrate a single-camera imaging system that can simultaneously acquire brightfield, darkfield, and phase contrast images in real time. Our method uses computational illumination via a programmable light-emitting diode (LED) array at the source plane, providing flexible patterning of illumination angles. Brightfield, darkfield, and differential phase contrast images are obtained by changing the LED patterns, without any moving parts. Previous work with LED array illumination was only valid for static samples because the hardware speed was not fast enough to meet real-time acquisition and processing requirements. Here, we time multiplex patterns for each of the three contrast modes in order to image dynamic biological processes in all three contrast modes simultaneously. We demonstrate multicontrast operation at the maximum frame rate of our camera (50 Hz with 2160 ū 2560 pixels). PMID:25271540
Coupled-mode analysis of gain and wavelength oscillation characteristics of diode laser phased arrays
J. K. Butler; M. Ettenberg; D. E. Ackley
The lasing wavelengths and gain characteristics of the modes of phase-locked arrays of channel-substrate-planar (CSP) lasers are presented. The gain values for the array modes are determined from complex coupling coefficients calculated using the fields of neighboring elements of the array. The computations show that, for index guided lasers which have nearly planar phase fronts, the highest order array mode
Technique for Radiometer and Antenna Array Calibration with a Radiated Noise Diode
NASA Technical Reports Server (NTRS)
Srinivasan, Karthik; Limaye, Ashutosh; Laymon, Charles; Meyer, Paul
This paper presents a new technique to calibrate a microwave radiometer and antenna array system. This calibration technique uses a radiated noise source in addition to two calibration sources internal to the radiometer. The method accurately calibrates antenna arrays with embedded active devices (such as amplifiers) which are used extensively in active phased array antennas.
Localized surface plasmon-enhanced near-ultraviolet emission from InGaN/GaN light-emitting diodes using silver and platinum nanoparticles.
Hong, Sang-Hyun; Cho, Chu-Young; Lee, Sang-Jun; Yim, Sang-Youp; Lim, Wantae; Kim, Sung-Tae; Park, Seong-Ju
We demonstrate localized surface plasmon (LSP)-enhanced near-ultraviolet light-emitting diodes (NUV-LEDs) using silver (Ag) and platinum (Pt) nanoparticles (NPs). The optical output power of NUV-LEDs with metal NPs is higher by 20.1% for NUV-LEDs with Ag NPs and 57.9% for NUV-LEDs with Pt NPs at 20 mA than that of NUV-LEDs without metal NPs. The time-resolved photoluminescence (TR-PL) spectra shows that the decay times of NUV-LEDs with Ag and Pt NPs are faster than that of NUV-LEDs without metal NPs. The TR-PL and absorbance spectra of metal NPs indicate that the spontaneous emission rate is increased by resonance coupling between excitons in the multiple quantum wells and LSPs in the metal NPs. PMID:23481772
Nitrogen doped MgxZn1-xO/ZnO single heterostructure ultraviolet light-emitting diodes on ZnO substrates
NASA Astrophysics Data System (ADS)
Nakahara, K.; Akasaka, S.; Yuji, H.; Tamura, K.; Fujii, T.; Nishimoto, Y.; Takamizu, D.; Sasaki, A.; Tanabe, T.; Takasu, H.; Amaike, H.; Onuma, T.; Chichibu, S. F.; Tsukazaki, A.; Ohtomo, A.; Kawasaki, M.
We have grown nitrogen-doped MgxZn1-xO:N films on Zn-polar ZnO single crystal substrates by molecular beam epitaxy. As N-sources, we employed NO-plasma or NH3 gas itself. As x increased, optimum growth temperature window for smooth film morphology shifted to higher temperatures, while maintaining high N-concentration (ś1ū1019 cm-3). The heterosructures of MgxZn1-xO:N (0.1?x?0.4)/ZnO were fabricated into light emitting diodes of 500-?m-diameter. We observed ultraviolet near-band-edge emission (? ś382 nm) with an output power of 0.1 ?W for a NO-plasma-doped LED and 70 ?W for a NH3-doped one at a bias current of 30 mA.
The improvement of deep-ultraviolet light-emitting diodes with gradually decreasing Al content in AlGaN electron blocking layers
NASA Astrophysics Data System (ADS)
Zhang, Yuanwen; Yu, Lei; Li, Kai; Pi, Hui; Diao, Jiasheng; Wang, Xingfu; Shen, Yue; Zhang, Chongzhen; Hu, Wenxiao; Song, Weidong; Li, Shuti
Deep-ultraviolet light-emitting diodes (DUV-LEDs) with conventional and specifically designed electron blocking layers (EBLs) are numerical investigated with APSYS simulation program. The results show that the internal quantum efficiency (IQE) and light output power are significantly improved by using a AlGaN EBL with gradually decreasing Al content compared to the conventional EBL with constant Al content and the EBL with gradually increasing Al content. These improvement are mainly attributed to the lower polarization field in EBL and active region as well as the alleviation of band bending in the EBL/p-GaN interface, which lead to less electron leakage and better hole injection efficiency, thus enhance the radiative recombination rate.
Light interaction in sapphire/MgF2/Al triple-layer omnidirectional reflectors in AlGaN-based near ultraviolet light-emitting diodes
Lee, Keon Hwa; Moon, Yong-Tae; Song, June-O; Kwak, Joon Seop
This study examined systematically the mechanism of light interaction in the sapphire/MgF2/Al triple-layer omnidirectional reflectors (ODR) and its effects on the light output power in near ultraviolet light emitting diodes (NUV-LEDs) with the ODR. The light output power of NUV-LEDs with the triple-layer ODR structure increased with decreasing surface roughness of the sapphire backside in the ODR. Theoretical modeling of the roughened surface suggests that the dependence of the reflectance of the triple-layer ODR structure on the surface roughness can be attributed mainly to light absorption by the Al nano-structures and the trapping of scattered light in the MgF2 layer. Furthermore, the ray tracing simulation based upon the theoretical modeling showed good agreement with the measured reflectance of the ODR structure in diffuse mode. PMID:26010378
Transparent conductive oxide films mixed with gallium oxide nanoparticle/single-walled carbon nanotube layer for deep ultraviolet light-emitting diodes
NASA Astrophysics Data System (ADS)
Kim, Kyoeng Heon; An, Ho-Myoung; Kim, Hee-Dong; Kim, Tae Geun
We propose a transparent conductive oxide electrode scheme of gallium oxide nanoparticle mixed with a single-walled carbon nanotube (Ga2O3 NP/SWNT) layer for deep ultraviolet light-emitting diodes using spin and dipping methods. We investigated the electrical, optical and morphological properties of the Ga2O3 NP/SWNT layers by increasing the thickness of SWNTs via multiple dipping processes. Compared with the undoped Ga2O3 films (current level 9.9 ū 10-9 A @ 1 V, transmittance 68% @ 280 nm), the current level flowing in the Ga2O3 NP/SWNT increased by approximately 4 ū 105 times and the transmittance improved by 9% after 15 times dip-coating (current level 4 ū 10-4 A at 1 V; transmittance 77.0% at 280 nm). These improvements result from both native high transparency of Ga2O3 NPs and high conductivity and effective current spreading of SWNTs.
Edge-emitting ultraviolet n-ZnO:Al/i-ZnO/p-GaN heterojunction light-emitting diode with a rib waveguide.
Liang, H K; Yu, S F; Yang, H Y
An edge-emitting ultraviolet n-ZnO:Al/i-ZnO/p-GaN heterojunction light-emitting diode with a rib waveguide is fabricated by filtered cathodic vacuum arc technique at low deposition temperature (approximately 150 degrees C). Electroluminescence with emission peak at 387 nm is observed. Good correlation between electro- and photo- luminescence spectra suggests that the i-ZnO layer of the heterojunction supports radiative excitonic recombination. Furthermore, it is found that the emission intensity can be enhanced by approximately 5 times due to the presence of the rib waveguide. Only fundamental TE and TM polarizations are supported inside the rib waveguide and the intensity of TE polarization is approximately 2.2 time larger than that of TM polarization. PMID:20389378
Numerical analysis on the effects of multi-quantum last barriers in AlGaN-based ultraviolet light-emitting diodes
NASA Astrophysics Data System (ADS)
Chen, Shengchang; Li, Yang; Tian, Wu; Zhang, Min; Li, Senlin; Wu, Zhihao; Fang, Yanyan; Dai, Jiangnan; Chen, Changqing
The advantages of AlGaN-based ultraviolet light-emitting diode with AlGaN/AlGaN multi-quantum last barrier (MQLB) are investigated numerically in this work. The light output power, internal quantum efficiency, energy band diagrams, carrier concentrations, radiative recombination rate, and spontaneous emission spectra in the multi-quantum wells are investigated. The simulation results show that the structure with MQLB exhibits higher output power and smaller efficiency droop at high current as compared to the conventional one. Based on the numerical simulation and analysis, these improvements on the device characteristics are attributed to the remarkable improvement of the hole injection efficiency from p-type region, which results from the lower effective barrier height for hole transportation, the lower consumption of holes in the p-side, and the very low hole population in MQLB region.
Light interaction in sapphire/MgF2/Al triple-layer omnidirectional reflectors in AlGaN-based near ultraviolet light-emitting diodes.
Lee, Keon Hwa; Moon, Yong-Tae; Song, June-O; Kwak, Joon Seop
This study examined systematically the mechanism of light interaction in the sapphire/MgF2/Al triple-layer omnidirectional reflectors (ODR) and its effects on the light output power in near ultraviolet light emitting diodes (NUV-LEDs) with the ODR. The light output power of NUV-LEDs with the triple-layer ODR structure increased with decreasing surface roughness of the sapphire backside in the ODR. Theoretical modeling of the roughened surface suggests that the dependence of the reflectance of the triple-layer ODR structure on the surface roughness can be attributed mainly to light absorption by the Al nano-structures and the trapping of scattered light in the MgF2 layer. Furthermore, the ray tracing simulation based upon the theoretical modeling showed good agreement with the measured reflectance of the ODR structure in diffuse mode. PMID:26010378
Monolithic arrays of grating-surface-emitting diode lasers and quantum well modulators for optical communications
NASA Technical Reports Server (NTRS)
Carlson, N. W.; Evans, G. A.; Liew, S. K.; Kaiser, C. J.
The electro-optic switching properties of injection-coupled coherent 2-D grating-surface-emitting laser arrays with multiple gain sections and quantum well active layers are discussed and demonstrated. Within such an array of injection-coupled grating-surface-emitting lasers, a single gain section can be operated as intra-cavity saturable loss element that can modulate the output of the entire array. Experimental results demonstrate efficient sub-nanosecond switching of high power grading-surface-emitting laser arrays by using only one gain section as an intra-cavity loss modulator.
An automated method for the determination of carbendazim in water that combines high-performance immunoaffinity chromatography (HPIAC), high-performance liquid chromatography (HPLC) in the reversed-phase mode, and detection by either UV-Vis diode array detector (DAD) spectroscopy...
Determination of robenidine in animal feeds by liquid chromatography coupled with diode-array detection and mass spectrometry after accelerated solvent extraction
Agata Kot-Wasik; Andrzej Wasik
A rapid and effective analytical procedure for the determination of robenidine in animal feeds was developed. Robenidine was extracted from samples with acidified methanol using accelerated solvent extraction (ASE). Extracts were dried and subjected to clean-up with aluminium oxide. Robenidine was eluted with methanol and determined by HPLC using UV diode-array (DAD) and MS detectors. Separation was carried out on
Characterization of flavonoids in the extract of Sophora flavescens Ait. by high-performance liquid chromatography coupled with diode-array detector and electrospray ionization mass spectrometry
Lei Zhang; Liang Xu; Shan-Shan Xiao; Qiong-Feng Liao; Qing Li; Jian Liang; Xiao-Hui Chen; Kai-Shun Bi
A method coupling high-performance liquid chromatography (HPLC) with diode-array detector (DAD) and electrospray ionization mass spectrometry (ESI) was established for the separation and characterization of flavonoids in Sophora flavescens Ait. Based on the chromatographic separation of most flavonoids present in S. flavescens Ait., a total of 24 flavonoids were identified. Fourteen compounds were unambiguously identified comparing experimental data for retention
Synthesis and photoluminescence of novel NaLi2PO4:Tb(3+) nanophosphors for near-ultraviolet excited light emitting diodes.
Shinde, K N; Dhoble, S J; Yoon, S J; Park, K
A series of Tb(3+)-activated NaLi2PO4 novel nano-crystalline phosphors was synthesized by the solution combustion method. The prepared Na(1-x)Li2PO4:xTb(3+) (0.01 ? x ? 0.1) phosphors crystallized in the orthorhombic crystal structure. Its effective absorption in the near ultraviolet range allowed highly efficient green emission. The Na(1-x)Li2PO4:xTb(3+) phosphors showed characteristic (5)D4 --> (7)FJ (J = 3, 4, 5, and 6) transitions of Tb(3+), i.e., (5)D4 --> (7)F6 (488 nm), (5)D4 --> (7)F5 (545 nm), (5)D4 --> (7)F4 (583 nm), and (5)D4 --> (7)F3 (622 nm). The Na0.95Li2PO4:0.05Tb(3+) phosphor showed the most excellent emission efficiency. The present work suggests that the Na0.95Li2PO4:0.05Tb(3+) is a potential green-emitting phosphor for near ultraviolet excited light emitting diodes. PMID:25936035
Application of a diode-laser-based ultraviolet absorption sensor for in situ measurements of atomic mercury in coal-combustion exhaust
Jesse K. Magnuson; Thomas N. Anderson; Robert P. Lucht; Udayasarathy A. Vijayasarathy; Hyukjin Oh; Kalyan Annamalai; Jerald A. Caton [Purdue University, West Lafayette, IN (United States). School of Mechanical Engineering
A diode-laser-based ultraviolet absorption sensor was successfully demonstrated for both in situ and extractive sampling atomic mercury measurements in a laboratory-scale 29.3 kWt (100 000 BTU/h) coal combustor and in situ measurements in a flow reactor at Texas A&M University. Laser sensor measurements were compared to measurements from a commercial mercury analyzer (CMA). A 375 nm single-mode laser and a 784 nm distributed feedback (DFB) laser are sum-frequency-mixed in a nonlinear {beta}-barium borate crystal to generate a 254 nm beam. By tuning the frequency of the DFB laser, the ultraviolet beam frequency was tuned across the transition frequency of mercury at 253.7 nm. The tuning range was large enough that an off-resonant baseline was clearly visible on both sides of the Hg transition. No pretreatment is required for elemental mercury measurements, and the effects of broadband absorption can be effectively eliminated during data analysis. Extractive sampling was demonstrated to improve the detection limit of the sensor and demonstrate the feasibility of total mercury concentration measurements in the future through extractive sampling. Significant variation in the atomic mercury concentration of coal-combustion exhaust was observed over short time periods during our in situ measurements. The sensor detection limits for in situ and extractive sampling are 0.3 and 0.1 parts per billion over a 1 m path length, respectively. 34 refs., 11 figs., 2 tabs.
Determination of furanic compounds in traditional balsamic vinegars by ion-exclusion liquid chromatography and diode-array detection.
Chinnici, Fabio; Masino, Francesca; Antonelli, Andrea
A method for the determination of furanic compounds in traditional balsamic vinegars is proposed. It is based on ion-exclusion chromatographic separation and diode-array detection of furans through an isocratic elution with 0.01 N phosphoric acid and 16% acetonitrile. Preliminary trials on standard compounds stability in heat-acidic conditions are also performed. In all the 19 samples analyzed, 2-furoic acid, 5 HMF, and furfural are found. No sample contains 4-hydroxy-2,5-dimethyl-3-(2H)-furanone (DHMF); 2-acetylfuran; or furfuryl alcohol. Three unknown compounds are also detected. The last eluting of these compounds is identified as 5-acethoxymethylfurfural, and, notwithstanding a partial hydrolysis in our chromatographic conditions, its quantitation can be carried out. PMID:12935302
Generation of laser-polarized xenon using fiber-coupled laser-diode arrays narrowed with integrated volume holographic gratings.
Nikolaou, Panayiotis; Whiting, Nicholas; Eschmann, Neil A; Chaffee, Kathleen E; Goodson, Boyd M; Barlow, Michael J
Volume holographic gratings (VHGs) can be exploited to narrow the spectral output of high-power laser-diode arrays (LDAs) by nearly an order of magnitude, permitting more efficient generation of laser-polarized noble gases for various applications. A approximately 3-fold improvement in (129)Xe nuclear spin polarization, P(Xe), (compared to a conventional LDA) was achieved with the VHG-LDA's center wavelength tuned to a wing of the Rb D(1) line. Additionally, an anomalous dependence of P(Xe) on the xenon density within the OP cell is reported-including high P(Xe) values (>10%) at high xenon partial pressures (approximately 1000 torr). PMID:19162517
Recover soft x-ray spectrum using virtual flat response channels with filtered x-ray diode array
Song Tianming; Yang Jiamin; Yi Rongqing [Reach Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China)
A method for the recovery of soft x-ray spectra in indirect-drive inertial confinement fusion experiments is presented. Virtual detection channels with bandpass responses are obtained using linear combinations of the channel response functions of a filtered x-ray diode array and a weighted correction is introduced to improve the recovery. These virtual channels can be used to calculate radiation fluxes in some specific photon energy bands and hence to recover the spectrum of the whole photon energy range from 80 eV to 4.5 keV. Examples are listed which demonstrate the capability of this method to unfold various spectra such as Planck spectra with different radiation temperatures and to obtain x-ray flux of certain narrow energy interval.
Recover soft x-ray spectrum using virtual flat response channels with filtered x-ray diode array.
Tianming, Song; Jiamin, Yang; Rongqing, Yi
A method for the recovery of soft x-ray spectra in indirect-drive inertial confinement fusion experiments is presented. Virtual detection channels with bandpass responses are obtained using linear combinations of the channel response functions of a filtered x-ray diode array and a weighted correction is introduced to improve the recovery. These virtual channels can be used to calculate radiation fluxes in some specific photon energy bands and hence to recover the spectrum of the whole photon energy range from 80 eV to 4.5 keV. Examples are listed which demonstrate the capability of this method to unfold various spectra such as Planck spectra with different radiation temperatures and to obtain x-ray flux of certain narrow energy interval. PMID:23206046
Recover soft x-ray spectrum using virtual flat response channels with filtered x-ray diode array
NASA Astrophysics Data System (ADS)
Tianming, Song; Jiamin, Yang; Rongqing, Yi
A method for the recovery of soft x-ray spectra in indirect-drive inertial confinement fusion experiments is presented. Virtual detection channels with bandpass responses are obtained using linear combinations of the channel response functions of a filtered x-ray diode array and a weighted correction is introduced to improve the recovery. These virtual channels can be used to calculate radiation fluxes in some specific photon energy bands and hence to recover the spectrum of the whole photon energy range from 80 eV to 4.5 keV. Examples are listed which demonstrate the capability of this method to unfold various spectra such as Planck spectra with different radiation temperatures and to obtain x-ray flux of certain narrow energy interval.
Floral classification of honey using liquid chromatography-diode array detection-tandem mass spectrometry and chemometric analysis.
Zhou, Jinhui; Yao, Lihu; Li, Yi; Chen, Lanzhen; Wu, Liming; Zhao, Jing
A high performance liquid chromatography-diode array detection-tandem mass spectrometry (HPLC-DAD-MS/MS) method for the floral origin traceability of chaste honey and rape honey samples was firstly presented in this study. Kaempferol, morin and ferulic acid were used as floral markers to distinguish chaste honey from rape honey. Chromatographic fingerprinting at 270 nm and 360 nm could be used to characterise chaste honey and rape honey according to the analytical profiles. Principal component analysis (PCA), partial least squares (PLS), partial least squares-discrimination analysis (PLS-DA) and soft independent modeling of class analogy (SIMCA) were applied to classify the honey samples according to their floral origins. The results showed that chaste honey and rape honey could be successfully classified by their floral sources with the analytical methods developed through this study and could be considered encouraging and promising for the honey traceability from unifloral or multifloral nectariferous sources. PMID:24128567
Rapid method for the determination of 14 isoflavones in food using UHPLC coupled to photo diode array detection.
Shim, You-Shin; Yoon, Won-Jin; Hwang, Jin-Bong; Park, Hyun-Jin; Seo, Dongwon; Ha, Jaeho
A rapid method for the determination of 14 types of isoflavones in food using ultra-high performance liquid chromatography (UHPLC) was validated in terms of precision, accuracy, sensitivity and linearity. The UHPLC separation was performed on a reverse-phase C18 column (particle size 2?m, i.d. 2mm, length 100mm) using a photo diode array detector that was fixed to 260nm. The limits of detection and quantification of the UHPLC analyses ranged from 0.03 to 0.33mgkg(-1). The intra-day and inter-day precision of the individual isoflavones were less than 11.77% and calibration curves exhibited good linearity (r(2)=0.99) within the tested ranges. These results suggest that the rapid method used in this study could be available to determine of 14 types of isoflavones in a variety of food such as soy bean, black bean, red bean and soybean paste. PMID:25977042
Variable-color light-emitting diodes using GaN microdonut arrays.
Tchoe, Youngbin; Jo, Janghyun; Kim, Miyoung; Heo, Jaehyuk; Yoo, Geonwook; Sone, Cheolsoo; Yi, Gyu-Chul
Microdonut-shaped GaN/Inx Ga1-x N light-emitting diode (LED) microarrays are fabricated for variable-color emitters. The figure shows clearly donut-shaped light emission from all the individual microdonut LEDs. Furthermore, microdonut LEDs exhibit spatially-resolved blue and green EL colors, which can be tuned by either controlling the external bias voltage or changing the size of the microdonut LED. PMID:24677202
Vertically p-n-junctioned GaN nano-wire array diode fabricated on Si(111) using MOCVD.
Park, Ji-Hyeon; Kim, Min-Hee; Kissinger, Suthan; Lee, Cheul-Ro
We demonstrate the fabrication of n-GaN:Si/p-GaN:Mg nanowire arrays on (111) silicon substrate by metal organic chemical vapor deposition (MOCVD) method .The nanowires were grown by a newly developed two-step growth process. The diameter of as-grown nanowires ranges from 300-400 nm with a density of 6-7 ū 10(7) cm(-2). The p- and n-type doping of the nanowires is achieved with Mg and Si dopant species. Structural characterization by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) indicates that the nanowires are relatively defect-free. The room-temperature photoluminescence emission with a strong peak at 370 nm indicates that the n-GaN:Si/p-GaN:Mg nanowire arrays have potential application in light-emitting nanodevices. The cathodoluminscence (CL) spectrum clearly shows a distinct optical transition of GaN nanodiodes. The nano-n-GaN:Si/p-GaN:Mg diodes were further completed using a sputter coating approach to deposit Au/Ni metal contacts. The polysilazane filler has been etched by a wet chemical etching process. The n-GaN:Si/p-GaN:Mg nanowire diode was fabricated for different Mg source flow rates. The current-voltage (I-V) measurements reveal excellent rectifying properties with an obvious turn-on voltage at 1.6 V for a Mg flow rate of 5 sccm (standard cubic centimeters per minute). PMID:23455517
Effect of chip spacing on light extraction for light-emitting diode array.
Chung, Shuang-Chao; Ho, Pei-Chen; Li, Dun-Ru; Lee, Tsung-Xian; Yang, Tsung-Hsun; Sun, Ching-Cherng
GaN LED array in packaging is important for the demand of high optical flux. In order to tighten the whole packaging size, the spacing among LED chips becomes an important factor in the packaging design. This study is to investigate the change of the light extraction when a GaN LED chip array packaging is applied. The shielding effect with various spacing for the GaN LED array with or without silicon encapsulation is obtained. We apply the Monte Carlo ray-tracing method in the simulations to analyze the optical behavior of the two major types of the GaN LED array. The shielding effect is more dominant for bare chip packaging. When a silicone thin dispensing layer is applied, the shielding effect is not obvious because of more light extraction, the neighbor dies play an important role in photon recycling. PMID:26072888
Over 1000 channel nitride-based micro-light-emitting diode arrays with tunnel junctions
NASA Astrophysics Data System (ADS)
Watanabe, Masahiro; Nakajima, Keisuke; Kaga, Mitsuru; Kuwano, Yuka; Minamikawa, Daichi; Suzuki, Tomoyuki; Yamashita, Kouji; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu
We fabricated nitride-based micro-LED arrays with a small number of fabrication process steps by using a combination of tunnel junctions and patterned n-GaN cathode lines. A use of the combination enables us to skip a couple of process steps required in standard LED array fabrication. A 10 ū 10 channel matrix-addressable LED array with a 10 ū 16 Ąm2 emission regions and a 25 Ąm pitch lengths showed uniform operating voltages and light output intensities, indicating good yield due to the small number of process steps used. In addition, microdisplay of over 1000 (14 ū 72) channels was successfully demonstrated. The new array structure with the tunnel junction and n-GaN cathode line provides a high density and a high yield simultaneously.
Technique for Radiometer and Antenna Array Calibration with Two Antenna Noise Diodes
NASA Technical Reports Server (NTRS)
Srinivasan, Karthik; Limaye, Ashutosh; Laymon, Charles; Meyer, Paul
This paper presents a new technique to calibrate a microwave radiometer and phased array antenna system. This calibration technique uses a radiated noise source in addition to an injected noise sources for calibration. The plane of reference for this calibration technique is the face of the antenna and therefore can effectively calibration the gain fluctuations in the active phased array antennas. This paper gives the mathematical formulation for the technique and discusses the improvements brought by the method over the existing calibration techniques.
Ultraviolet-assisted synthesis of encapsulating adhesives and their application for lifetime improvement of organic light emitting diodes
Chen-Ming Chen; Ming-Hua Chung; Tsung-Eong Hsieh; Bohr-Ran Huang; Huai-En Hsieh; Fuh-Shyang Juang; Yu-Sheng Tsai; Mark O. Liu; Jen-Lien Lin
The lifetimes of organic light emitting diodes (OLEDs) have been successfully enhanced with the modulation of LiF thickness and the utilization of encapsulating adhesives, which have been successfully and quickly synthesized with UV irradiation. Experimental results demonstrate that LiF and lab-made encapsulating adhesives can block the invasion of moisture as well as oxygen in the atmosphere into the OLEDs so
Light-emitting diode arrays and photodynamic therapy: a progress report
NASA Astrophysics Data System (ADS)
Schlager, Kenneth J.; Straight, Richard C.
A laboratory version of an LED-array light source centered at 664 nm was reviewed last year in Biomedical Optics '93. Since that time, primary development efforts have been directed toward the development of two LED-array light sources for preclinical trials, one centered at 630 nm and the other at 800 nm. The first array is targeted as an alternative to the argon- pumped dye laser for photodynamic therapy (PDT) procedures based on the Photofrin II photosensitizer. The second array at 800 nm is directed at deep tissue penetration with a new photosensitizer recently developed at the University of Utah, bacteriochlorin derivative (bcd). While the first array is viewed as a lower-cost, more reliable, user-friendly replacement for traditional PDT dye lasers, the second is being developed in unison with bcd to significantly expand the range of applications of PDT to previously undeveloped cancer treatment modalities such as breast cancer. The 800 nm array has demonstrated an optical output of 5.13 watts while the 630 nm source radiates with a maximum optical power output of 1.63 watts.
Ultra high brightness laser diode arrays for pumping of compact solid state lasers and direct applications
NASA Astrophysics Data System (ADS)
Kohl, Andreas; Fillardet, Thierry; Laugustin, Arnaud; Rabot, Olivier
High Power Laser Diodes (HPLD) are increasingly used in different fields of applications such as Industry, Medicine and Defense. Our significant improvements of performances (especially in power and efficiency) and a reproducible manufacturing process have led to reliable, highly robust components. For defense and security applications these devices are used predominantly for pumping of solid state lasers (ranging, designation, countermeasures, and sensors). Due to the drastically falling price per watt they are more and more replacing flash lamps as pump sources. By collimating the laser beam even with a bar to bar pitch of only 400?m. cutting edge brightness of our stacks.is achieved Due the extremely high brightness and high power density these stacks are an enabling technology for the development of compact highly efficient portable solid state lasers for applications as telemeters and designators on small platforms such as small UAVs and handheld devices. In combination with beam homogenizing optics their compact size and high efficiency makes these devices perfectly suited as illuminators for portable active imaging systems. For gated active imaging systems a very short pulse at high PRF operation is required. For this application we have developed a diode driver board with an efficiency several times higher than that of a standard driver. As a consequence this laser source has very low power consumption and low waste heat dissipation. In combination with its compact size and the integrated beam homogenizing optics it is therefore ideally suited for use in portable gated active imaging systems. The kWatt peak power enables a range of several hundred meters. The devices described in this paper mostly operate at wavelength between 800 nm and 980nm. Results from diodes operating between 1300 nm and 1550 nm are presented as well.
Discrimination of the Hoechst side population in mouse bone marrow with violet and near-ultraviolet laser diodes
William G. Telford; Ella G. Frolova
Background: Discrimination of stem cells with flow cy- tometric analysis of Hoechst 33342 efflux by the ABCG2 transporter (termed the Hoechst side population ,o rSP technique) is a valuable methodology for identifying bone marrow progenitors enriched with stem cells. Unfortu- nately, it requires a ultraviolet (UV) laser source, usually necessitating an expensive and maintenance-intensive ar- gon- or krypton-ion gas laser
Quantum efficiency of opaque CsI photocathodes with channel electron multiplier arrays in the extreme and far ultraviolet
NASA Technical Reports Server (NTRS)
Martin, C.; Bowyer, S.
The arrays are overcoated with a CsI photocathode in the VUV. The measurements are part of the development program for the Extreme Ultraviolet Explorer. Monochromatic light from a hollow cathode discharge source passing through a McPherson grazing incidence monochromator is used to illuminate the CsI photocathode. The beam diameter is kept small (approximately 2 mm) to confine it within the individual thickness strips. A bias grid is used to produce a 50-V/mm electric field to guarantee collection of all photoelectrons emitted by the CEMA (channel electron multiplier array) webbing. The CEMAs are operated with a gain of 2-3 x 10 to the 6th and are moderately saturated. A channeltron secondary transfer standard is used to determine the absolute QE in the EUV, whereas an NBS calibrated windowed photodiode is used to measure the FUV absolute QE. It is noted that the CsI gives a factor of 3 increase in the QE in the EUV and a factor of 50-5000 in the FUV.
Quasi-isotropic VHF antenna array design study for the International Ultraviolet Explorer satellite
NASA Technical Reports Server (NTRS)
Raines, J. K.
Results of a study to design a quasi-isotropic VHF antenna array for the IUE satellite are presented. A free space configuration was obtained that has no nulls deeper than -6.4 dbi in each of two orthogonal polarizations. A computer program named SOAP that analyzes the electromagnetic interaction between antennas and complicated conducting bodies, such as satellites was developed.
Feasibility of High-Power Diode Laser Array Surrogate to Support Development of Predictive Laser Lethality Model
Lowdermilk, W H; Rubenchik, A M; Springer, H K
Predictive modeling and simulation of high power laser-target interactions is sufficiently undeveloped that full-scale, field testing is required to assess lethality of military directed-energy (DE) systems. The cost and complexity of such testing programs severely limit the ability to vary and optimize parameters of the interaction. Thus development of advanced simulation tools, validated by experiments under well-controlled and diagnosed laboratory conditions that are able to provide detailed physics insight into the laser-target interaction and reduce requirements for full-scale testing will accelerate development of DE weapon systems. The ultimate goal is a comprehensive end-to-end simulation capability, from targeting and firing the laser system through laser-target interaction and dispersal of target debris; a 'Stockpile Science' - like capability for DE weapon systems. To support development of advanced modeling and simulation tools requires laboratory experiments to generate laser-target interaction data. Until now, to make relevant measurements required construction and operation of very high power and complex lasers, which are themselves costly and often unique devices, operating in dedicated facilities that don't permit experiments on targets containing energetic materials. High power diode laser arrays, pioneered by LLNL, provide a way to circumvent this limitation, as such arrays capable of delivering irradiances characteristic of De weapon requires are self-contained, compact, light weight and thus easily transportable to facilities, such as the High Explosives Applications Facility (HEAF) at Lawrence Livermore National Laboratory (LLNL) where testing with energetic materials can be performed. The purpose of this study was to establish the feasibility of using such arrays to support future development of advanced laser lethality and vulnerability simulation codes through providing data for materials characterization and laser-material interaction models and to validate the accuracy of code predictions. This project was a Feasibility Study under the LLNL Laboratory Directed Research and Development (LDRD) Program.
P-type Cu--Ti--O nanotube arrays and their use in self-biased heterojunction photoelectrochemical diodes for hydrogen generation.
Mor, Gopal K; Varghese, Oomman K; Wilke, Rudeger H T; Sharma, Sanjeev; Shankar, Karthik; Latempa, Thomas J; Choi, Kyoung-Shin; Grimes, Craig A
Copper and titanium remain relatively plentiful in the earth's crust; hence, their use for large-scale solar energy conversion technologies is of significant interest. We describe fabrication of vertically oriented p-type Cu-Ti-O nanotube array films by anodization of copper rich (60% to 74%) Ti metal films cosputtered onto fluorine doped tin oxide (FTO) coated glass. Cu-Ti-O nanotube array films 1 mum thick exhibit external quantum efficiencies up to 11%, with a spectral photoresponse indicating that the complete visible spectrum, 380 to 885 nm, contributes significantly to the photocurrent generation. Water-splitting photoelectrochemical pn-junction diodes are fabricated using p-type Cu-Ti-O nanotube array films in combination with n-type TiO 2 nanotube array films. With the glass substrates oriented back-to-back, light is incident upon the UV absorbing n-TiO 2 side, with the visible light passing to the p-Cu-Ti-O side. In a manner analogous to photosynthesis, photocatalytic reactions are powered only by the incident light to generate fuel with oxygen evolved from the n-TiO 2 side of the diode and hydrogen from the p-Cu-Ti-O side. To date, we find under global AM 1.5 illumination that such photocorrosion-stable diodes generate a photocurrent of approximately 0.25 mA/cm (2), at a photoconversion efficiency of 0.30%. PMID:18540655
Photoelectric characteristics of diodes in prototype photosensitive pixels for a monolithic array infrared photodetector
Sorochkin, A. V., E-mail: email@example.com; Varavin, V. S.; Predein, A. V.; Sabinina, I. V.; Yakushev, M. V. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)
Test photodiodes in the form of mesa structures with different areas from 30 Multiplication-Sign 30 to 100 Multiplication-Sign 100 {mu}m in size are fabricated based on a Cd{sub x}Hg{sub 1-x}Te/Si structure at x = 0.235, grown by molecular-beam epitaxy (MBE). The current-voltage characteristics of the diodes are measured in the dark and under background light conditions. The experimental results are compared with theoretical calculations. It is found that the dependence of the photodiode photocurrent and dark current on the mesa structure size appears in the mesa size ranges from 30 Multiplication-Sign 30 to 80 Multiplication-Sign 80 {mu}m. The dark current decreases and the photocurrent increases with decreasing mesa size. The mechanisms affecting the behavior of current-voltage characteristics are discussed.
Characterization of narrow-band near-IR diodes arranged in array patterns
Antonio Ortega; Gonzalo Paez; Marija Strojnik
We examined old, not-well documented paintings before the process of restoration was started, to look for the presence of any invisible signatures and dates, as well as original line drawings and possible painted-over or hidden images. We connected IR LEDs in two-dimensional arrays to allow us to sample the surface of the artwork with approximately uniform illumination, but at different
Integrated electronics for time-resolved array of single-photon avalanche diodes
NASA Astrophysics Data System (ADS)
Acconcia, G.; Crotti, M.; Rech, I.; Ghioni, M.
The Time Correlated Single Photon Counting (TCSPC) technique has reached a prominent position among analytical methods employed in a great variety of fields, from medicine and biology (fluorescence spectroscopy) to telemetry (laser ranging) and communication (quantum cryptography). Nevertheless the development of TCSPC acquisition systems featuring both a high number of parallel channels and very high performance is still an open challenge: to satisfy the tight requirements set by the applications, a fully parallel acquisition system requires not only high efficiency single photon detectors but also a read-out electronics specifically designed to obtain the highest performance in conjunction with these sensors. To this aim three main blocks have been designed: a gigahertz bandwidth front-end stage to directly read the custom technology SPAD array avalanche current, a reconfigurable logic to route the detectors output signals to the acquisition chain and an array of time measurement circuits capable of recording the photon arrival times with picoseconds time resolution and a very high linearity. An innovative architecture based on these three circuits will feature a very high number of detectors to perform a truly parallel spatial or spectral analysis and a smaller number of high performance time-to-amplitude converter offering very high performance and a very high conversion frequency while limiting the area occupation and power dissipation. The routing logic will make the dynamic connection between the two arrays possible in order to guarantee that no information gets lost.
Characterization and calibration of compact array spectrometers in the ultraviolet spectral region
Shindo, Francois [Measurement Standards Laboratory of New Zealand, Industrial Research, Lower Hutt (New Zealand); Woolliams, Emma; Scott, Barry; Harris, Subrena [National Physical Laboratory, Teddington (United Kingdom)
Array-based spectrometers, with their compact size, low weight, low cost, and fast measurement time, are now frequently used in place of both conventional single-channel scanning monochromators, and broadband meters. Their rapid measurement capability makes them an attractive option for routine solar UV spectral measurements, where shortterm variability in signal is a challenge. However, compactness, portability, low cost and high speed are achieved at the expense of the spectrometer's optical and electronic performance. Thus such spectrometers are more prone to measurement error from environmental changes, and more prone to other intrinsic sources of error such as stray light and detector non-linearity, which significantly affect solar UV measurements, than a scanning monochromator. The effects of stray light and non-linearity can be reduced either by improved optical and detector design or by a detailed spectrometer characterization. We present in this paper our investigation of the performance of three different commercial array spectrometers: two mini-spectrometers, and a more elaborate array spectrometer with an on-board image amplifier device. These were tested for a subset of performance parameters: their wavelength accuracy and stability, electronic linearity, responsivity linearity, stray light sensitivity, and mechanical stability and repeatability. With all three spectrometers we found that these parameters, particularly but not limited to stray light, had a significant impact on the measurement of the incoming optical radiation. This meant that, without characterization, the instruments would be unable to accurately measure the UV component of any source with significant visible radiation. We discuss various simple and low-cost solutions for improving the performance of these instruments, and providing a rigorous calibration using a straightforward set-up including optical filters and the quasi-monochromatic light from a double monochromator.
Determination of analytes in medical herbs extracts by SPE coupled with two-dimensional planar chromatography in combination with diode array scanning densitometry and HPLC-diode array detector.
Tuzimski, Tomasz
The purpose of this study is to demonstrate an application of 2-D high-performance planar chromatography-diode array detector (DAD) and HPLC-DAD after solid-phase extraction (SPE) for identification and quantitative analysis of pesticides (isoproturon, aziprotryne, hexazinone, flufenoxuron, methabenzthiazuron, procymidone, and ?-cypermethrin) in Melissa officinalis L. (Labiatae) samples. The procedure described for the determination of compounds is inexpensive and can be applied to routine analysis of analytes in medical herbs' samples after preliminary cleanup and concentration by SPE. Average recoveries on C18 SPE cartridges of pesticides eluted with 5 mL tetrahydrofuran by the proposed HPLC-DAD method, before and after 2-D-high-performance planar chromatography separation of analytes from M. officinalis L. samples spiked with pesticide at a concentration level of 10 ?g/g in plant material are presented. Method validation parameters for the quantification of pesticides by the proposed HPLC-DAD after SPE method are also presented. PMID:21171173
Thermally stable white-emitting single composition Na(Sr,Ba)PO4:Eu2+, Mn2+ phosphor for near-ultraviolet-pumped light-emitting diodes.
Choi, Sungho; Yun, Young Jun; Kim, Sue Jin; Jung, Ha-Kyun
Eu(2+) and Mn(2+) codoped, white-emitting Na(Sr,Ba)PO(4) phosphors are prepared, and their emission properties, especially for thermal stability, are thoroughly investigated. The thermal quenching and Eu(2+)/Mn(2+) energy transfer efficiency are totally different in the ratio of alkaline earth metals in host composition, NaBaPO(4), Na(Sr(0.5)Ba(0.5))PO(4), and NaSrPO(4), respectively. Furthermore, by using near-ultraviolet light-emitting diodes (LEDs) and the corresponding Na(Sr(0.5)Ba(0.5))PO(4):Eu(2+), Mn(2+) phosphor as light converters, we demonstrate a bright and thermally stable white-emitting LED. The resultant LED exhibits a warm white light [~4900 K, CIE coordinates of (0.33, 0.31)] with excellent thermal and hydrolytic stabilities comparable to those of commercially available ones, Y(3)Al(5)O(12):Ce(3+) and BaMg(2)Al(16)O(27):Eu(2+). The proposed composition, with its efficient energy transfer, could enable Eu(2+) and Mn(2+) codoped Na(Sr,Ba)PO(4) to be a promising single component phosphor for cost-effective white-emitting LEDs. PMID:23595480
Luminescent properties of Eu2+-doped BaGdF5 glass ceramics a potential blue phosphor for ultra-violet light-emitting diode
NASA Astrophysics Data System (ADS)
Zhang, Weihuan; Zhang, Yuepin; Ouyang, Shaoye; Zhang, Zhixiong; Wang, Qian; Xia, Haiping
Eu2+ doped transparent oxyfluoride glass ceramics containing BaGdF5 nanocrystals were successfully fabricated by melt-quenching technique under a reductive atmosphere. The structure of the glass and glass ceramics were investigated by differential scanning calorimetry, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The luminescent properties were investigated by transmission, excitation, and emission spectra. The decay time of the Gd3+ ions at 312 nm excited with 275 nm were also investigated. The results of XRD and TEM indicated the existence of BaGdF5 nanocrystals in the transparent glass ceramics. The excitation spectra of Eu2+ doped glass ceramics showed an excellent overlap with the main emission region of an ultraviolet light-emitting diode (UV-LED). Compared with the as-made glass, the emission of glass ceramics is much stronger by a factor of increasing energy transfer efficiency from Gd3+ to Eu2+ ions, the energy transfer efficiency from Gd3+ to Eu2+ ions was discussed. In addition, the chromaticity coordinates of glass and glass ceramics specimens were also discussed, which indicated that the Eu2+ doped BaGdF5 glass ceramics may be used as a potential blue-emitting phosphor for UV-LED.
Efficiency improvement of GaN-based ultraviolet light-emitting diodes with reactive plasma deposited AlN nucleation layer on patterned sapphire substrate
NASA Astrophysics Data System (ADS)
Lee, Chia-Yu; Tzou, An-Jye; Lin, Bing-Cheng; Lan, Yu-Pin; Chiu, Ching-Hsueh; Chi, Gou-Chung; Chen, Chi-Hsiang; Kuo, Hao-Chung; Lin, Ray-Ming; Chang, Chun-Yen
The flip chip ultraviolet light-emitting diodes (FC UV-LEDs) with a wavelength of 365 nm are developed with the ex situ reactive plasma deposited (RPD) AlN nucleation layer on patterned sapphire substrate (PSS) by an atmospheric pressure metal-organic chemical vapor deposition (AP MOCVD). The ex situ RPD AlN nucleation layer can significantly reduce dislocation density and thus improve the crystal quality of the GaN epitaxial layers. Utilizing high-resolution X-ray diffraction, the full width at half maximum of the rocking curve shows that the crystalline quality of the epitaxial layer with the (RPD) AlN nucleation layer is better than that with the low-temperature GaN (LT-GaN) nucleation layer. The threading dislocation density (TDD) is estimated by transmission electron microscopy (TEM), which shows the reduction from 6.8 ū 107 cm-2 to 2.6 ū 107 cm-2. Furthermore, the light output power (LOP) of the LEDs with the RPD AlN nucleation layer has been improved up to 30 % at a forward current of 350 mA compared to that of the LEDs grown on PSS with conventional LT-GaN nucleation layer.
Disinfection of B. SUBTILIS Cells in Suspension Using Ultraviolet Light Emitting Diodes (leds) in the Presence of TiO2
NASA Astrophysics Data System (ADS)
Province, Dennis W.; O'Neil, Shannon; Higgins, Keri; Smith, Paul J.; Dooley, Kristin; Curtis, Joey; Grippo, Adam M.; Rino, John W.; Allen, Susan D.
The concentration of vegetative Bacillus subtilis (B. subtilis) in phosphate buffered saline decreased when subjected to ultraviolet (UV) light from light emitting diodes (LEDs) in the presence of 0.01% Degussa P25 titanium dioxide (TiO2) as compared to a sample that contained bacteria only, a sample of bacteria that contained 0.01% TiO2, and bacteria that was subjected to the same UV light but no TiO2. The starting concentration of each sample was on the order of 104 colony forming units per milliliter (CFU/mL) and the time required for complete kill was less than 100min when the peak wavelength was 370 nm for the four LED light source at a total LED power of 0.8 milliWatts (mW), decreasing to less than 75 min for a total LED power of 3 mW. Changing the peak wavelength by 7 nm to 377 nm decreased the kill of vegetative B. subtilis to less than 1 log at 100 min for 5 mW total LED power. This work was performed under Federal Contract W9113M-09-C-0136 in support of the Radiance Technologies, Inc., prime contract from US Army SMDC, Huntsville, AL.
Near milliwatt power AlGaN-based ultraviolet light emitting diodes based on lateral epitaxial overgrowth of AlN on Si(111)
NASA Astrophysics Data System (ADS)
Zhang, Yinjun; Gautier, Simon; Cho, Chu-Young; Cicek, Erdem; Vashaei, Zahra; McClintock, Ryan; Bayram, Can; Bai, Yanbo; Razeghi, M.
We report on the growth, fabrication, and device characterization of AlGaN-based thin-film ultraviolet (UV) (? ś 359 nm) light emitting diodes (LEDs). First, AlN/Si(111) template is patterned. Then, a fully coalesced 7-?m-thick lateral epitaxial overgrowth (LEO) of AlN layer is realized on patterned AlN/Si(111) template followed by UV LED epi-regrowth. Metalorganic chemical vapor deposition is employed to optimize LEO AlN and UV LED epitaxy. Back-emission UV LEDs are fabricated and flip-chip bonded to AlN heat sinks followed by Si(111) substrate removal. A peak pulsed power and slope efficiency of ś0.6 mW and ś1.3 ?W/mA are demonstrated from these thin-film UV LEDs, respectively. For comparison, top-emission UV LEDs are fabricated and back-emission LEDs are shown to extract 50% more light than top-emission ones.
Detection, characterization and identification of crucifer phytoalexins using high-performance liquid chromatography with diode array detection and electrospray ionization mass spectrometry
M. Soledade C. Pedras; Adewale M. Adio; Mojmir Suchy; Denis P. O. Okinyo; Qing-An Zheng; Mukund Jha; Mohammed G. Sarwar
We have analyzed 23 crucifer phytoalexins (e.g. brassinin, dioxibrassinin, cyclobrassinin, brassicanals A and C) by HPLC with diode array detection and electrospray ionization mass spectrometry (HPLC-DAD¢ESI-MS) using both negative and positive ion modes. Positive ion mode ESI-MS appeared more sensitive than negative ion mode ESI-MS in detecting this group of compounds. A new HPLC separation method, new LC¢MS and LC¢MS2
Three-dimensional mapping of quantum wells in a GaN/InGaN core-shell nanowire light-emitting diode array.
Riley, James R; Padalkar, Sonal; Li, Qiming; Lu, Ping; Koleske, Daniel D; Wierer, Jonathan J; Wang, George T; Lauhon, Lincoln J
Correlated atom probe tomography, cross-sectional scanning transmission electron microscopy, and cathodoluminescence spectroscopy are used to analyze InGaN/GaN multiquantum wells (QWs) in nanowire array light-emitting diodes (LEDs). Tomographic analysis of the In distribution, interface morphology, and dopant clustering reveals material quality comparable to that of planar LED QWs. The position-dependent CL emission wavelength of the nonpolar side-facet QWs and semipolar top QWs is correlated with In composition. PMID:23919559
Analysis of xanthohumol and isoxanthohumol in different hop products by liquid chromatography-diode array detection-electrospray ionization tandem mass spectrometry
Paulo J. MagalhŃes; LuĒs F. Guido; Josķ M. Cruz; Aquiles A. Barros
An analytical methodology based on the sample extraction with methanol\\/formic acid by ultra-sonication and subsequent analysis by high-performance liquid chromatography with diode array detection is proposed for the determination of xanthohumol (XN) and isoxanthohumol (IXN) in different hop products. The identity of the compounds was confirmed by high-performance liquid chromatography\\/electrospray ionization tandem mass spectrometry in positive ion mode. The performance
Determination of propoxur residues in eggs by liquid chromatography¢diode array detection after treatment of stocked housing facilities for the poultry red mite ( Dermanyssus gallinae)
Gerd Hamscher; Beate Prie▀; J÷rg Hartung; Monika I. Nogossek; Gerhard Gl³nder; Heinz Nau
A sensitive and selective liquid chromatography¢diode array detection method for the determination of propoxur in eggs is described. Eggs were homogenized, extracted with acetonitrile and partitioned with n-hexane. Further clean-up of the acetonitrile extract was undertaken using silica gel column chromatography. Quantitative detection was performed by liquid chromatography with UV detection at 220nm and confirmation of the residue was achieved
Determination of Melamine and Derivatives in Foods by Liquid Chromatography Coupled to Atmospheric Pressure Chemical Ionization Mass Spectrometry and Diode Array Detection
Pilar Vi±as; Natalia Campillo; Gema Fķrez-Melgarejo; Manuel Hernßndez-C¾rdoba
Two liquid chromatographic methods based on atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS) and diode array detection (DAD) are evaluated for the rapid determination of melamine (MEL) and structurally related compounds, including ammeline (AMN), ammelide (AMD) and cyanuric acid (CA) in foods. Both procedures used ion-exchange LC and isocratic elution. Samples were extracted by homogenization with acetonitrile\\/water\\/diethylamine. Specificity was demonstrated
Characterization of aquatic dissolved organic matter by asymmetrical flow field-flow fractionation coupled to UV¢Visible diode array and excitation emission matrix fluorescence
Cķline Guķguen; Chad W. Cuss
Flow field-flow fractionation (FlFFF) with on-line UV\\/Visible diode array detector (DAD) and excitation emission matrix (EEM) fluorescence detector has been developed for the characterization of optical properties of aquatic dissolved organic matter (DOM) collected in the Otonabee River (Ontario, Canada) and Athabasca River (Alberta, Canada). The molecular weight (MW) distribution of DOM was estimated using a series of organic macromolecules
Dispersive liquid¢liquid microextraction followed by high-performance liquid chromatography-diode array detection as an efficient and sensitive technique for determination of antioxidants
Mir Ali Farajzadeh; Morteza Bahram; Jan ┼ke J÷nsson
Dispersive liquid¢liquid microextraction (DLLME) and high performance liquid chromatography-diode array detection (HPLC-DAD) was presented for extraction and determination of Irganox 1010, Irganox 1076 and Irgafos 168 (antioxidants) in aqueous samples. Carbon tetrachloride at microliter volume level and acetonitrile were used as extraction and dispersive solvents, respectively. The main advantages of method are high speed, high enrichment factor, high recovery, good
Quasi-CW 110 kW AlGaAs Laser Diode Array Module for Inertial Fusion Energy Laser Driver
NASA Astrophysics Data System (ADS)
Kawashima, Toshiyuki; Kanzaki, Takeshi; Matsui, Ken; Kato, Yoshinori; Matsui, Hiroki; Kanabe, Tadashi; Yamanaka, Masanobu; Nakatsuka, Masahiro; Izawa, Yasukazu; Nakai, Sadao; Miyamoto, Masahiro; Kan, Hirofumi; Hiruma, Teruo
We have successfully demonstrated a large aperture 803 nm AlGaAs diode laser module as a pump source for a 1053 nm, 10 J output Nd:glass slab laser amplifier for diode-pumped solid-state laser (DPSSL) fusion driver. Detailed performance results of the laser diode module are presented, including bar package and stack configuration, and their thermal design and analysis. A sufficiently low thermal impedance of the stack was realized by combining backplane liquid cooling configuration with modular bar package architecture. Total peak power of 110 kW and electrical to optical conversion efficiency of 46% were obtained from the module consisting of a total of 1000 laser diode bars. A peak intensity of 2.6 kW/cm2 was accomplished across an emitting area of 418 mmū 10 mm. Currently, this laser diode array module with a large two-dimensional aperture is, to our knowledge, the only operational pump source for the high output energy DPSSL.
Low-noise low-jitter 32-pixels CMOS single-photon avalanche diodes array for single-photon counting from 300 nm to 900 nm
Scarcella, Carmelo; Tosi, Alberto, E-mail: firstname.lastname@example.com; Villa, Federica; Tisa, Simone; Zappa, Franco [Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy)] [Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy)
We developed a single-photon counting multichannel detection system, based on a monolithic linear array of 32 CMOS SPADs (Complementary Metal-Oxide-Semiconductor Single-Photon Avalanche Diodes). All channels achieve a timing resolution of 100 ps (full-width at half maximum) and a photon detection efficiency of 50% at 400 nm. Dark count rate is very low even at room temperature, being about 125 counts/s for 50 ?m active area diameter SPADs. Detection performance and microelectronic compactness of this CMOS SPAD array make it the best candidate for ultra-compact time-resolved spectrometers with single-photon sensitivity from 300 nm to 900 nm.
Out-of-plane high-density piezoresistive silicon microwire/p-n diode array for force- and temperature-sensitive artificial whisker sensors
NASA Astrophysics Data System (ADS)
Ikedo, Akihito; Ishida, Makoto; Kawano, Takeshi
We propose an out-of-plane high-aspect-ratio 'whisker-like' microwire array sensor for use in multisite contact force and temperature detection with high spatial resolution. Although the wire element has two terminal electrodes, the device consists of force-sensitive wire arrays where one end of the wire is attached to the substrate and the other end is free to be touched. We fabricated a force-sensitive wire array based on p-type (p-) silicon with 3 Ąm diameter and 30 Ąm length (1 ? cm) assembled over an n-type (n-) silicon substrate (3-6 ? cm), which resulted in a p-silicon wire/p-n diode system array. Due to the piezoresistance effect of the p-silicon wire, the electrical conductance changes upon contact of an individual wire with an object. The shift in the rectifying current-voltage (I-V) curves of the embedded p-n diode depends on the temperature through the silicon wire. Thus, the same alignment can be used as a force sensor and a temperature sensor. Both force- and temperature-sensitive microwire sensor arrays with a small detection area (~20 Ąm2) and high spatial resolution (~100 Ąm in pitch) have potential in numerous applications, including artificial electronic fingertips in a robot hand/prosthetics, multisite sensing of contact force, shear force, surface roughness and slip, and local temperature sensing capabilities.
Characterization of narrow-band near-IR diodes arranged in array patterns
NASA Astrophysics Data System (ADS)
Ortega, Antonio; Paez, Gonzalo; Strojnik, Marija
We examined old, not-well documented paintings before the process of restoration was started, to look for the presence of any invisible signatures and dates, as well as original line drawings and possible painted-over or hidden images. We connected IR LEDs in two-dimensional arrays to allow us to sample the surface of the artwork with approximately uniform illumination, but at different peak wavelengths. We describe the extended area infrared LED illumination sources as to their geometrical arrangement, and their resulting spectral, spatial, and power output characteristics. With these light sources, we were able to make invisible information available for review and critical assessment by the art historians.
Vacuum ultraviolet radiation and thermal cycling effects on atomic oxygen protective photovoltaic array blanket materials
NASA Technical Reports Server (NTRS)
Brady, J.; Banks, B.
The importance of synergistic environmental exposure is demonstrated through the evaluation of DuPont 93-1 in simulated LEO environment. Changes in optical properties, surface condition, and mass loss data are described. The qualitative results indicate the necessity for exposure of materials to a series of simulated LEO environments in order to properly determine synergistic effects and demonstrate the overall LEO durability of candidate materials. It is shown that synergistic effects may occur with vacuum thermal cycling combined with VUV radiation followed by atomic oxygen exposure. Testing the durability of candidate solar array blanket materials in a test sequence with necessary synergistic effects makes it possible to determine the appropriate material for providing structural support and maintaining the proper operating temperature for solar cells in the SSF Photovaltaic Power System.
Liquid chromatographic-diode-array detection multiresidue determination of rice herbicides in drinking and paddy-field water.
Roehrs, Rafael; Zanella, Renato; Pizzuti, Ionara; Adaime, Martha B; Pareja, LucĒa; Niell, Silvina; Cesio, MarĒa V; Heinzen, Horacio
A sensitive, rapid, and simple multiresidue method for the simultaneous determination of six postemergence herbicides currently used in rice cultivation--metsulfuron methyl, bensulfuron methyl, pyrazosulfuron ethyl, bentazone, bispyribac sodium, and cyhalofop butyl--in drinking and paddy-field water is presented. Water samples were extracted with solid-phase extraction cartridges. Final determination was made by LC with diode-array detection. The extraction efficiencies of C18 and HLB cartridges were compared. The average recovery obtained for these compounds for the lowest spiked level (0.1 microg/L) varied from 70 to 122% for C18 and 75-119% for HLB, with RSDs of 11 and 8.3%, respectively. The method had good linearity, and the lower detection limit for the pesticides studied varied from 0.03 to 0.04 microg/L. The proposed method was also tested in paddy-field water, with recovery studies giving good results with low RSDs at 1.0 microg/L. PMID:19714989
Application of RP-HPLC-diode array detector after SPE to the determination of pesticides in pepper samples.
Tuzimski, Tomasz
The application of HPLC-diode array detector (DAD) after SPE for identification and quantitative analysis of pesticides in red and green pepper samples is demonstrated. An HPLC procedure on an RP column (C18) was developed for analysis of selected pesticides from different chemical groups: metamitron, metalaxyl, linuron, and prometryn. Average recoveries for C18 Polar Plus cartridges and solvents by the proposed RP-HPLC-DAD method after SPE are presented. Average recoveries from the spiked samples and the SDs were 22.5 +/- 2.2, 138.0 +/- 4.1, 78.6 +/- 2.8, and 109.2 +/- 2.3% for metamitron, metalaxyl, linuron, and prometryn, respectively, at concentrations of 7 microg/g in the plant material. The efficiency of the SPE procedure was evaluated using real food samples. The quantities of prometryn, linuron, metalaxyl, and metamitron determined were in the ranges of 0.02-2.24 microg/g (n = 24), 0.08-1.01 microg/g (n = 9), 1.61-2.28 microg/g (n=4), and 0.05-1.07 microg/g (n = 3), respectively, in plant material sampled in 2011. The method was validated for precision, repeatability, and accuracy. PMID:23175966
A simultaneous determination of principal compounds in tokishakuyakusan by high-performance liquid chromatography with diode array detector.
Sumino, Megumi; Saito, Yuko; Ikegami, Fumio; Namiki, Takao
We developed a simultaneous analysis method using high-performance liquid chromatography coupled with diode-array detector (HPLC-DAD) for six principal compounds (atractylenolide III, alisol A, alisol B, paeoniflorin, ferulic acid and (Z)-ligustilide) in a traditional Japanese (Kampo) medicine, tokishakuyakusan (TSS). The HPLC separation was conducted on a reversed-phase TSK-gel ODS-80TS column (4.6 i.d. ū 250 mm, 5 Ąm) at 40░C with a 0.1% phosphoric acid-acetonitrile gradient system. The DAD detection wavelength was set at 205, 232 and 330 nm. Calibration curves for the compounds showed linear regressions with correlation coefficients of >0.999. The intra- and inter-day precision (i.e., the relative standard deviation) were in the range of 0.50-1.55 and 0.70-1.80%, respectively. The average recovery yields of the compounds ranged from 98.3 to 103%. The present results will contribute to shorter analysis times with less organic solvent compared with the individual analysis of each compound for the evaluation of TSS. The application of the established method to TSS will also provide helpful information for the further pharmacological and clinical studies. PMID:24981981
Light extraction enhancement of GaN based light emitting diodes by ZnO nanorod arrays.
Choi, Pan-Ju; Kim, Ja-Yeon; Kang, Young-Jin; Kwon, Min-Ki
This study examined the effects of the alignment of ZnO nanorod arrays (NRAs) on the light extraction enhancement of GaN-based light emitting diodes (LEDs), where ZnO NRAs were synthesized hydrothermally. The shape of the ZnO NRAs was controlled using seed layers for flower and vertical structures. Numerical analysis based on the two-dimensional (2D) finite difference of time domain (FDTD) method showed that the extraction efficiency of LED with bare (without ZnO NRA), vertical ZnO NRA and flower shaped ZnO NRA was 37%, 60% and 49%, respectively. The optical output power of the LEDs with vertical ZnO NRA and flower ZnO NRA was improved by 50% and 30% compared to that of the LED without ZnO NRA at an input current of 100 mA. These results suggest that the vertical alignment of ZnO NRA is important for enhancing the light extraction of GaN based LEDs. PMID:25936037
Simultaneous determination of 11 bioactive compounds in Jaeumganghwa-tang by high performance liquid chromatography-diode array detection
Yun, Bo-Ra; Weon, Jin Bae; Lee, Jiwoo; Eom, Min Rye; Ma, Choong Je
Background: Jaeumganghwa-tang (JEGH) is a traditional Korean herbal medicine for the treatment of chronic bronchitis, nephritis and diabetes mellitus. Objective: A high performance liquid chromatography-diode array detector (HPLC-DAD) method was developed for simultaneous determination of 11 major compounds such as 5- hydroxymethylfurfural, mangiferin, paeoniflorin, nodakenin, naringin, hesperidin, decursinol, berberine, glycyrrhizin, atractylenolide III and decursin, in JEGH. Materials and Methods: The separation was conducted on Shishedo C18 column with gradient elution of 0.1% trifluoroacetic acid¢acetonitrile. Detection of wavelength was set at 205, 250, 280 and 330 nm. Results: The developed analysis showed a good linearity (R2 >0.9997). The range of limit of detection and limit of quantification were observed from 0.04 to 0.43 and from 0.11 to 1.30, respectively. The intra- and inter-day test relative standard deviations (RSD) were less than 3% and the accuracy was 95.98-108.44%. The recoveries were between 92.75% and 109.19% and RSD range of recoveries was measured from 0.52% to 2.78%. Conclusion: This HPLC-DAD method can be successfully applied for simultaneous determination of 11 major compounds in JEGH samples. PMID:24991100
Simultaneous determination of four neuroprotective compounds of Tilia amurensis by high performance liquid chromatography coupled with diode array detector
Lee, Bohyung; Weon, Jin Bae; Yun, Bo-Ra; Lee, Jiwoo; Eom, Min Rye; Ma, Choong Je
Background: Tilia amurensis consists of various compounds, such as flavonoids and terpenoids. Objective: A simple and reliable high performance liquid chromatography (HPLC) coupled with the diode array detector (DAD) method has been established for simultaneous determination of epicatechin, nudiposide, lyoniside, and scopoletin isolated from Tilia amurensis. Materials and Methods: Optimum separations were obtained with a SHISEIDO C18 column by gradient eluton, with 0.1% Trifluoroacetic acid (TFA) water-methanol as the mobile phase. The gradient elution system was completed within 40 minutes. The flow rate and detection wavelength were 1 mL/minute, 205 nm, 250 nm, and 280 nm, respectively. Results: Validation of the analytical method was evaluated by linearity, precision, and the accuracy test. The calibration curve was linear over the established range with R2 > 0.997. The limit of detection (LOD) and limit of quantification (LOQ) ranged from 0.01-15.20 ?g/mL and 0.03-46.06 ?g/mL. The method exhibited an intraday and interday precision range of 96.25-105.66% and 93.52-109.92%, respectively (RSD <2.80%). The recoveries and relative standard deviation (RSD) of the four compounds in Tilia amurensis were in the range of 90.42-104.84% and 0.2-2.58%. Conclusion: This developed method was accurate and reliable for the quality evaluation of the four compounds isolated from Tilia amurensis. PMID:25210303
Epitaxial growth of InGaN nanowire arrays for light emitting diodes.
Hahn, Christopher; Zhang, Zhaoyu; Fu, Anthony; Wu, Cheng Hao; Hwang, Yun Jeong; Gargas, Daniel J; Yang, Peidong
Significant synthetic challenges remain for the epitaxial growth of high-quality InGaN across the entire compositional range. One strategy to address these challenges has been to use the nanowire geometry because of its strain relieving properties. Here, we demonstrate the heteroepitaxial growth of In(x)Ga(1-x)N nanowire arrays (0.06 ? x ? 0.43) on c-plane sapphire (Al(2)O(3)(001)) using a halide chemical vapor deposition (HCVD) technique. Scanning electron microscopy and X-ray diffraction characterization confirmed the long-range order and epitaxy of vertically oriented nanowires. Structural characterization by transmission electron microscopy showed that single crystalline nanowires were grown in the ?002? direction. Optical properties of InGaN nanowire arrays were investigated by absorption and photoluminescence measurements. These measurements show the tunable direct band gap properties of InGaN nanowires into the yellow-orange region of the visible spectrum. To demonstrate the utility of our HCVD method for implementation into devices, LEDs were fabricated from In(x)Ga(1-x)N nanowires epitaxially grown on p-GaN(001). Devices showed blue (x = 0.06), green (x = 0.28), and orange (x = 0.43) electroluminescence, demonstrating electrically driven color tunable emission from this p-n junction. PMID:21495684
High-performance liquid chromatography-diode array and electrospray-mass spectrometry analysis of non-allowed substances in cosmetic products for preventing hair loss and other hormone-dependent skin diseases.
De Orsi, Daniela; Pellegrini, Manuela; Pichini, Simona; Mattioli, Donatella; Marchei, Emilia; Gagliardi, Luigi
A simple high-performance liquid chromatography (HPLC) method with ultraviolet diode array (UV-DAD) and electrospray ionisation mass spectrometry (ESI-MS) detection has been developed for the determination of minoxidil, progesterone, estrone, spironolactone, canrenone, hydrocortisone and triamcinolone acetonide in cosmetic products. The presence of these substances in commercial cosmetic samples is prohibited. The compounds were separated by reversed phase chromatography with water (0.1% trifluoroacetic acid) and acetonitrile gradient elution and detected by UV-DAD at 230, 254 and 280 nm and by ESI-MS positive ionisation mode. Benzoic acid was used as internal standard. Linearity was studied with UV-DAD detection from 1.50 to 1,000 microg/ml or mug/g range, depending on the different compounds and type of cosmetic preparation and with ESI-MS in the 50-1,000 ng/ml or ng/g range. Good determination coefficients (r(2)>or=0.99) were found in both UV and ESI-MS. At three concentrations spanning the linear dynamic ranges of both UV-DAD and ESI-MS assay, mean recoveries were always higher than 90% for the different analytes. This method was successfully applied to the analysis of substances under investigations illegally added in cosmetic cream and lotions, sold on internet web sites to prevent hair loss and other hormone-dependent skin diseases, like acne and hirsutism. PMID:18656319
Enhanced light emission in vertical-structured GaN-based light-emitting diodes with trench etching and arrayed p-electrodes
NASA Astrophysics Data System (ADS)
Lin, Tseng-Hsing; Wang, Shui-Jinn; Tu, Yung-Chun; Hung, Chien-Hsiung; Lin, Che-An; Lin, Yung-Cheng; You, Zong-Sian
We investigate the effect of trench etching and arrayed p-electrodes in improving current spreading and the efficiency of light extraction of GaN-based vertical-structured light-emitting diodes (VLEDs). Both simulated and experimental results on the uniformities of current distribution and light emission are presented and discussed. For a 2 ū 2 array VLED with a die size of 1020 ū 1020 ?m2, enhancements in light output power by 0.38% (6.03%) and wall-plug efficiency by 2.79% (2.32%) at 364.4 mA/mm2 (728.9 mA/mm2) as compared with that of regular VLED are achieved experimentally, which are attributed to improved current spreading from the arrayed p-electrode and trench designs as well as enhanced light emission from the trench region.
Electroluminescence of ordered ZnO nanorod array/p-GaN light-emitting diodes with graphene current spreading layer
Ordered ZnO nanorod array/p-GaN heterojunction light-emitting diodes (LEDs) have been fabricated by introducing graphene as the current spreading layer, which exhibit improved electroluminescence performance by comparison to the LED using a conventional structure (indium-tin-oxide as the current spreading layer). In addition, by adjusting the diameter of ZnO nanorod array in use, the light emission of the ZnO nanorod array/p-GaN heterojunction LEDs was enhanced further. This work has great potential applications in solid-state lighting, high performance optoelectronic devices, and so on. PACS 78.60.Fi; 85.60.Jb; 78.67.Lt; 81.10.Dn PMID:25489284
The effect of free-standing GaN substrate on carrier localization in ultraviolet InGaN light-emitting diodes.
Tsai, Ming-Ta; Chu, Chung-Ming; Huang, Che-Hsuan; Wu, Yin-Hao; Chiu, Ching-Hsueh; Li, Zhen-Yu; Tu, Po-Min; Lee, Wei-I; Kuo, Hao-Chung
In this study, we have grown 380-nm ultraviolet light-emitting diodes (UV-LEDs) based on InGaN/AlInGaN multiple quantum well (MQW) structures on free-standing GaN (FS-GaN) substrate by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD), and investigated the relationship between carrier localization degree and FS-GaN. The micro-Raman shift peak mapping image shows low standard deviation (STD), indicating that the UV-LED epi-wafer of low curvature and MQWs of weak quantum-confined Stark effect (QCSE) were grown. High-resolution X-ray diffraction (HRXRD) analyses demonstrated high-order satellite peaks and clear fringes between them for the UV-LEDs grown on the FS-GaN substrate, from which the interface roughness (IRN) was estimated. The temperature-dependent photoluminescence (PL) measurement confirmed that the UV-LEDs grown on the FS-GaN substrate exhibited better carrier confinement. Besides, the high-resolution transmission electron microscopy (HRTEM) and energy-dispersive spectrometer (EDS) mapping images verified that the UV-LEDs on FS-GaN have fairly uniform distribution of indium and more ordered InGaN/AlInGaN MQW structure. Clearly, the FS-GaN can not only improve the light output power but also reduce the efficiency droop phenomenon at high injection current. Based on the results mentioned above, the FS-GaN can offer UV-LEDs based on InGaN/AlInGaN MQW structures with benefits, such as high crystal quality and small carrier localization degree, compared with the UV-LEDs on sapphire. PMID:26088993
High performance 380-nm ultraviolet light-emitting-diodes with 3% efficiency droop by using free-standing GaN substrate manufacturing from GaAs substrate
NASA Astrophysics Data System (ADS)
Shieh, Chen-Yu; Tsai, Ming-Ta; Li, Zhen-Yu; Kuo, Hao-Chung; Chang, Jenq-Yang; Chi, Gou-Chung; Lee, Wei-I.
We investigated the influence of free-standing GaN (FS-GaN) substrates on the performance of ultraviolet light-emitting-diodes (UV-LEDs) grown on top by atmospheric pressure metal-organic chemical vapor deposition. High-resolution double-crystal x-ray diffraction (HRDCXD) analysis demonstrated high-order satellite peaks and clear fringes between them for UV-LEDs grown on the FS-GaN substrate, from which the interface roughness was estimated. In addition, the full width at half maximum of the HRDCXD rocking curve in the (0002) and the (10 1» 2) reflections were reduced to below 90 arc sec. The Raman results indicated that the GaN-based epilayer of strain free was grown. Additionally, the effect of the FS-GaN substrate on the crystal quality of the UV-LEDs was examined in detail by transmission electron microscopy (TEM). The TEM characterizations revealed no defects and V-pits were found in the scanned area. Based on the results mentioned above, the light output power of UV-LEDs on the FS-GaN substrate can be enhanced drastically by 80% and 90% at 20 and 100 mA, respectively. Furthermore, an ultralow efficiency degradation of about 3% can be obtained for the UV-LEDs on the FS-GaN substrate at a high injection current. The use of an FS-GaN substrate is suggested to be effective for improving the emission efficiency and droop of UV-LEDs grown thereon.
High power and high efficiency kW 88x-nm multi-junction pulsed diode laser bars and arrays
NASA Astrophysics Data System (ADS)
Chen, Zhigang; Bai, John; Dong, Weimin; Guan, Xingguo; Zhang, Shiguo; Elim, Sandrio; Bao, Ling; Grimshaw, Mike; Devito, Mark; Kanskar, Manoj
There is great interest in the development of high-power, high-efficiency and low cost QCW 88x-nm diode laser bars and arrays for pumping solid state lasers. We report on the development of kW 88x-nm diode laser bars that are based on a bipolar cascade design, in which multiple lasers are epitaxially grown in electrical series on a single substrate. Multiple laser junctions, each of which is based on nLight's high performance 88x-nm epitaxial design, are separated by low resistance tunnel junctions with resistance as low as 8.0x10-6 ?-cm2. Optimization of bar geometry and wafer fabrication processes was explored for electrical and optical performance improvement in double-junction diode lasers. A QCW power of 630 W was demonstrated in a 3-mm wide mini-bar with 3-mm cavity length. Peak efficiency of 61% was measured with 200 ?s and 14 Hz pulses, at a heatsink temperature of 10 ░C. Further power scaling was demonstrated in a 1-cm wide bar with 3-mm cavity length, where a record high peak power of 1.77 kW was measured at 1 kA drive current. Ongoing work for further power scaling includes development of triple-junction diode laser bars and double-junction bar-stack that emits < 10kW optical power.
Quantification of alpha-amanitin in biological samples by HPLC using simultaneous UV- diode array and electrochemical detection.
Garcia, Juliana; Costa, Vera M; Baptista, Paula; Bastos, Maria de Lourdes; Carvalho, Fķlix
?-Amanitin is a natural bicyclic octapeptide, from the family of amatoxins, present in the deadly mushroom species Amanita phalloides. The toxicological and clinical interests raised by this toxin, require highly sensitive, accurate and reproducible quantification methods for pharmacokinetic studies. In the present work, a high-performance liquid chromatographic (HPLC) method with in-line connected diode-array (DAD) and electrochemical (EC) detection was developed and validated to quantify ?-amanitin in biological samples (namely liver and kidney). Sample pre-treatment consisted of a simple and unique deproteinization step with 5% perchloric acid followed by centrifugation at 16,000ūg, 4░C, for 20min. The high recovery found for ?-amanitin (?96.8%) makes this procedure suitable for extracting ?-amanitin from liver and kidney homogenates. The resulting supernatant was collected and injected into the HPLC. Mobile phase was composed by 20% methanol in 50mM citric acid, and 0.46mM octanessulfonic acid, adjusted to pH 5.5. The chromatographic runs took less than 22min and no significant endogenous interferences were observed at the ?-amanitin retention time. Calibration curves were linear with regression coefficients higher than 0.994. The overall inter- and intra-assay precision did not exceed 15.3%. The present method has low interferences with simple and fast processing steps, being a suitable procedure to support in vivo toxicokinetic studies involving ?-amanitin. In fact, the validated method was successfully applied to quantify ?-amanitin in biological samples following intraperitoneal ?-amanitin administration to rats. Moreover, human plasma was also used as matrix and the purposed method was adequate for detection of ?-amanitin in that matrix. The results clearly indicate that the proposed method is suitable to investigate the pharmacokinetic and tissue distribution of ?-amanitin. Additionally, the method will be very useful in the development of novel and potent antidotes against amatoxins poisoning and to improve the knowledge of ?-amanitin toxicity. PMID:26100080
Determination of alkenes in cracking products by normal-phase high-performance liquid chromatography-diode array detection.
Tomi?, Tatjana; Babi?, Sandra; Nasipak, Nada Uzorinac; Ruszkowski, Maja Fabuli?; Skrobonja, Livijana; Kastelan-Macan, Marija
Alkene content determinations in fluid catalytic cracking (FCC) liquid products were performed by means of normal-phase high-performance liquid chromatography (NP-HPLC) with diode array detection (UV/DAD). Separation of alkenes from aromatic hydrocarbons was performed on amino-modified silica gel column with n-heptane as mobile phase. The column has a little affinity to alkenes and saturated hydrocarbons and a pronounced affinity to aromatic compounds. The problem of alkenes and saturates co-elution on this column type was overcome with the detection system, UV/DAD, sensitive and selective to alkenes, while saturates are inactive in UV field. Total alkene content was determined as a sum of mono- and dialkene groups quantified by external standard method. Validation and verification of the developed method proved their applicability. The following criteria were used to validate the HPLC-DAD method: selectivity, linearity, precision, limits of detection and quantification. Alkene contents were quantified with the external standard method of wide calibration range, so both low and high alkene contents can be determined by the single calibration. Correlation coefficients were higher than 0.99. Precision was evaluated as repeatability and intermediary precision with relative standard deviations less than 5%. Some structural investigation of alkene groups was performed to confirm the assumption. Proposed method was compared with certified NMR method. Six commercial motor gasoline samples were analyzed by these two methods. Obtained results indicate good agreement between alkene content determined by both methods. The developed method was applied to the determination of alkene content in liquid FCC products in the boiling range from 70 degrees C to 190 degrees C. PMID:19296961
Luminescent properties of Li 2 (Ca 0.99 , Eu 0.01 ) SiO 4 : B 3+ particles as a potential bluish green phosphor for ultraviolet light-emitting diodes
Shanshan Yao; Donghua Chen
In our study, the 1% mol Eu2+ doped Li2CaSiO4: B3+ phosphors were prepared by the combustion method as fluorescent material for ultraviolet, light-emitting diodes (UV-LEDs)\\u000a used as a light source. The properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ phosphors with urea concentration, doping boric acid and a series of initiating combustion temperature were investigated.\\u000a The crystallization and particle sizes of
Optical properties of a nanoporous array in silicon L. Tian, K. Bhargava Ram, I. Ahmad, L. Menon, and M. Holtza)
Holtz, Mark
efficiency of organic6 and ultraviolet (UV)7 light emitting diodes and reflectance properties.8 In Ref. 8 for controlling the path of light as it travels inside waveguides are of current interest.2 Lithography has been array of nanopores through an aluminum template under anodization. An aluminum oxide membrane is pro
NASA Technical Reports Server (NTRS)
2008-01-01[figure removed for brevity, see original site] Side-by-Side Comparison Click on image for larger view This ultraviolet image from NASA's Galaxy Evolution Explorer shows the Southern Pinwheel galaxy, also know as Messier 83 or M83. It is located 15 million light-years away in the southern constellation Hydra. Ultraviolet light traces young populations of stars; in this image, young stars can be seen way beyond the main spiral disk of M83 up to 140,000 light-years from its center. Could life exist around one of these far-flung stars? Scientists say it's unlikely because the outlying regions of a galaxy are lacking in the metals required for planets to form. The image was taken at scheduled intervals between March 15 and May 20, 2007. It is one of the longest-exposure, or deepest, images ever taken of a nearby galaxy in ultraviolet light. Near-ultraviolet light (or longer-wavelength ultraviolet light) is colored yellow, and far-ultraviolet light is blue. What Lies Beyond the Edge of a Galaxy The side-by-side comparison shows the Southern Pinwheel galaxy, or M83, as seen in ultraviolet light (right) and at both ultraviolet and radio wavelengths (left). While the radio data highlight the galaxy's long, octopus-like arms stretching far beyond its main spiral disk (red), the ultraviolet data reveal clusters of baby stars (blue) within the extended arms. The ultraviolet image was taken by NASA's Galaxy Evolution Explorer between March 15 and May 20, 2007, at scheduled intervals. Back in 2005, the telescope first photographed M83 over a shorter period of time. That picture was the first to reveal far-flung baby stars forming up to 63,000 light-years from the edge of the main spiral disk. This came as a surprise to astronomers because a galaxy's outer territory typically lacks high densities of star-forming materials. The newest picture of M83 from the Galaxy Evolution Explorer is shown at the right, and was taken over a longer period of time. In fact, it is one of the 'deepest,' or longest-exposure, images of a nearby galaxy in ultraviolet light. This deeper view shows more clusters of stars, as well as stars in the very remote reaches of the galaxy, up to 140,000 light-years away from its core. The view at the left is a combination of the ultraviolet picture at the right and data taken by the telescopes of the National Science Foundation's Very Large Array in New Mexico. The radio data, colored here in red, reveal extended galactic arms of gaseous hydrogen atoms, which are raw ingredients for stars. Astronomers are excited that the remote clusters of baby stars match up with the extended arms, because this helps them better understand how stars can be created out in the boondocks of a galaxy. M83 is located 15 million light-years away in the southern constellation Hydra. In the Galaxy Evolution Explorer image on the right, near-ultraviolet light (or longer-wavelength ultraviolet light) is colored yellow and far-ultraviolet light is blue. In the combined image at the left, far-ultraviolet light is blue, near-ultraviolet light is green, and the radio emission at a wavelength of 21 centimeters is red.
Rapid analysis of benzoylecgonine, cocaine, and cocaethylene in urine, serum, and saliva by isocratic high-performance liquid chromatography with diode-array detection
C. Foulon; M.-C. Menet; N. Manuel; C. Pham-Huy; H. Galons; J.-R. Claude; F. Guyon
SummaryĀĀAn isocratic high-performance liquid-chromatographic (HPLC) procedure with diode-array detection has been developed for the\\u000a determination of benzoylecgonine, cocaine, and cocaethylene in urine, serum, and saliva. After solid-phase extraction with\\u000a mixed-mode extraction cartridges the three solutes are separated, in less than 20 min, by HPLC on a Supelcosil ABZ+column\\u000a with 17?83 (v\\/v) acetonitrile-0.04 M phosphate buffer, pH 2.3, as mobile phase.
Optimizing the accuracy of a helical diode array dosimeter: A comprehensive calibration methodology coupled with a novel virtual inclinometer
Kozelka, Jakub; Robinson, Joshua; Nelms, Benjamin; Zhang, Geoffrey; Savitskij, Dennis; Feygelman, Vladimir [Sun Nuclear Corp., Melbourne, Florida 32940 (United States); Department of Physics, University of South Florida, Tampa, Florida 33612 (United States); Canis Lupus LLC, Sauk County, Wisconsin 53561 (United States); Division of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States); Sun Nuclear Corp., Melbourne, Florida 32940 (United States); Division of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States)
Purpose: The goal of any dosimeter is to be as accurate as possible when measuring absolute dose to compare with calculated dose. This limits the uncertainties associated with the dosimeter itself and allows the task of dose QA to focus on detecting errors in the treatment planning (TPS) and/or delivery systems. This work introduces enhancements to the measurement accuracy of a 3D dosimeter comprised of a helical plane of diodes in a volumetric phantom. Methods: We describe the methods and derivations of new corrections that account for repetition rate dependence, intrinsic relative sensitivity per diode, field size dependence based on the dynamic field size determination, and positional correction. Required and described is an accurate ''virtual inclinometer'' algorithm. The system allows for calibrating the array directly against an ion chamber signal collected with high angular resolution. These enhancements are quantitatively validated using several strategies including ion chamber measurements taken using a ''blank'' plastic shell mimicking the actual phantom, and comparison to high resolution dose calculations for a variety of fields: static, simple arcs, and VMAT. A number of sophisticated treatment planning algorithms were benchmarked against ion chamber measurements for their ability to handle a large air cavity in the phantom. Results: Each calibration correction is quantified and presented vs its independent variable(s). The virtual inclinometer is validated by direct comparison to the gantry angle vs time data from machine log files. The effects of the calibration are quantified and improvements are seen in the dose agreement with the ion chamber reference measurements and with the TPS calculations. These improved agreements are a result of removing prior limitations and assumptions in the calibration methodology. Average gamma analysis passing rates for VMAT plans based on the AAPM TG-119 report are 98.4 and 93.3% for the 3%/3 mm and 2%/2 mm dose-error/distance to agreement threshold criteria, respectively, with the global dose-error normalization. With the local dose-error normalization, the average passing rates are reduced to 94.6 and 85.7% for the 3%/3 mm and 2%/2 mm criteria, respectively. Some algorithms in the convolution/superposition family are not sufficiently accurate in predicting the exit dose in the presence of a 15 cm diameter air cavity. Conclusions: Introduction of the improved calibration methodology, enabled by a robust virtual inclinometer algorithm, improves the accuracy of the dosimeter's absolute dose measurements. With our treatment planning and delivery chain, gamma analysis passing rates for the VMAT plans based on the AAPM TG-119 report are expected to be above 91% and average at about 95% level for {gamma}(3%/3 mm) with the local dose-error normalization. This stringent comparison methodology is more indicative of the true VMAT system commissioning accuracy compared to the often quoted dose-error normalization to a single high value.
Precision Materials Processing Using Diode-Pumped Solid-
Van Stryland, Eric
Precision Materials Processing Using Diode-Pumped Solid- State (DPSS) Lasers Bruce B. Craig CREOL of Diode-Pumped Solid State Laser Technology Ę Review of Market for Diode-Pumped Solid State Lasers Ę Applications overview Ę Ultrafast materials processing #12;4 Diode Receptacle Diode Pump Pump Diode Array
Enhancement of light extraction in GaN-based light-emitting diodes using rough beveled ZnO nanocone arrays.
Yin, Zhengmao; Liu, Xiaoyan; Wu, Yongzhong; Hao, Xiaopeng; Xu, Xiangang
A remarkable enhancement of light extraction efficiency in GaN-based blue light-emitting diodes (LEDs) with rough beveled ZnO nanocone arrays grown on the planar indium tin oxide (ITO) layer is reported. The light output power of LEDs with rough beveled ZnO nanocone arrays was increased by about 110% at 20 mA compared with conventional LEDs with planar ITO. The light extraction efficiency of GaN-based LEDs with rough-beveled ZnO nanocones is measured much greater than with smooth-surface hexagonal ZnO nanorods. The light-ray tracing analysis showed that ZnO nanocones with rough surfaces enlarge the light escape cone of GaN-based LEDs and have a greater advantage for extracting light compared with ZnO nanorods. PMID:22274448
High-performance GaSb laser diodes and diode arrays in the 2.1-3.3 micron wavelength range for sensing and defense applications
NASA Astrophysics Data System (ADS)
Dvinelis, Edgaras; Trink┼½nas, Augustinas; Greibus, Mindaugas; KauÜylas, Mindaugas; Äukauskas, Tomas; ┼ imonyt─--, Ieva; Songaila, Ram┼½nas; Vizbaras, Augustinas; Vizbaras, Kristijonas
Mid-infrared spectral region (2-4 ?m) is gaining significant attention recently due to the presence of numerous enabling applications in the field of gas sensing, medical, and defense applications. Gas sensing in this spectral region is attractive due to the presence of numerous absorption lines for such gases as methane, ethane, ozone, carbon dioxide, carbon monoxide, etc. Sensing of the mentioned gas species is of particular importance for applications such as atmospheric LIDAR, petrochemical industry, greenhouse gas monitoring, etc. Defense applications benefit from the presence of covert atmospheric transmission window in the 2.1-2.3 micron band which is more eye-safe and offers less Rayleigh scattering than the conventional atmospheric windows in the near-infrared. Major requirement to enable these application is the availability of high-performance, continuous-wave laser sources in this window. Type-I GaSb-based laser diodes are ideal candidates for these applications as they offer direct emission possibility, high-gain and continuous wave operation. Moreover, due to the nature of type-I transition, these devices have a characteristic low operation voltage, which results in very low input powers and high wall-plug efficiency. In this work, we present recent results of 2 ?m - 3.0 ?m wavelength room-temperature CW light sources based on type-I GaSb developed at Brolis Semiconductors. We discuss performance of defense oriented high-power multimode laser diodes with < 1 W CW power output with over 30 % WPE as well as ~ 100 mW single TE00 Fabry-Perot chips. In addition, recent development efforts on sensing oriented broad gain superluminescent gain chips will be presented.
Far ultraviolet sensitivity of silicon CMOS sensors
NASA Astrophysics Data System (ADS)
Davis, Michael W.; Greathouse, Thomas K.; Retherford, Kurt D.; Winters, Gregory S.; Bai, Yibin; Beletic, James W.
We describe vacuum ultraviolet sensitivity measurements of a new high performance silicon-based CMOS sensor from Teledyne Imaging Sensors. These sensors do not require the high voltages of MCP detectors, making them a lower mass and power alternative to the more mature MCP technology. These devices demonstrate up to 40 percent quantum efficiency at vacuum ultraviolet wavelengths, either meeting or greatly exceeding 10 percent quantum efficiency across the entire 100-200 nm wavelength region. As with similar visible sensitive devices, backside illumination results in a higher quantum efficiency than frontside illumination. Measurements of the vacuum ultraviolet sensitivity of the Teledyne silicon PIN detectors were made by directing a known intensity of ultraviolet light at discrete wavelengths onto the test detectors and reading out the resulting photocurrent. The sensitivity of the detector at a given wavelength was then calculated from the intensity and wavelength of the incoming light and the relative photodiode to NIST-traceable calibration diode active areas. A custom electromechanical interface was developed to make these measurements within the SwRI Vacuum Radiometric Calibration Chamber. While still in the single pixel stage, full 1K ū 1K focal plane arrays are possible using existing CMOS readout electronics and hold great promise for inclusion in future spaceflight instrument concepts.
Monitoring of environmental arsenic by cultures of the photosynthetic bacterial sensor illuminated with a near-infrared light emitting diode array.
Maeda, Isamu; Sakurai, Hirokazu; Yoshida, Kazuyuki; Siddiki, Mohammad; Shimizu, Tokuo; Fukami, Motohiro; Ueda, Shunsaku
Recombinant Rhodopseudomonas palustris, harboring the carotenoid-metabolizing gene crtI (CrtIBS), and whose color changes from greenish yellow to red in response to inorganic As(III), was cultured in transparent microplate wells illuminated with a light emitting diode (LED) array. The cells were seen to grow better under near-infrared light, when compared with cells illuminated with blue or green LEDs. The absorbance ratio of 525 to 425 nm after cultivation for 24 h, which reflects red carotenoid accumulation, increased with an increase in As(III) concentrations. The detection limit of cultures illuminated with near-infrared LED was 5 microgram/l, which was equivalent to that of cultures in test tubes illuminated with an incandescent lamp. A near-infrared LED array, in combination with a microplate, enabled the simultaneous handling of multiple cultures, including CrtIBS and a control strain, for normalization by the illumination of those with equal photon flux densities. Thus, the introduction of a near-infrared LED array to the assay is advantageous for the monitoring of arsenic in natural water samples that may contain a number of unknown factors and, therefore, need normalization of the reporter event. PMID:22210618
GaSb quantum-well-based ``buffer-free'' vertical light emitting diode monolithically embedded within a GaAs cavity incorporating interfacial misfit arrays
NASA Astrophysics Data System (ADS)
Mehta, M.; Balakrishnan, G.; Huang, S.; Khoshakhlagh, A.; Jallipalli, A.; Patel, P.; Kutty, M. N.; Dawson, L. R.; Huffaker, D. L.
The authors demonstrate a monolithic, electrically injected, vertically emitting GaSb /AlGaSb light emitting diode (LED) emitting at 1.6?m comprised of a hybrid GaAs /GaSb-based structure. The LED is comprised of a GaSb /AlGaSb quantum well/barrier active region embedded within high index contrast GaAs /AlGaAs distributed Bragg reflectors (DBRs) using two interfacial misfit (IMF) arrays to relieve the strain induced from the high 8% lattice mismatch between the material systems. The first IMF is formed under compressive strain conditions to enable strain-free, defect-free deposition of GaSb active region directly on the lower GaAs /AlAs DBRs without need for thick buffer. The second IMF is formed under tensile conditions to enable the upper GaAs /AlAs DBRs on the GaSb active region. The device demonstrates a maximum output power of 3.5?W. Initial diode optical and electrical characteristics along with IMF band structure are discussed.
High efficiency 2 micrometer laser utilizing wing-pumped Tm{sup 3+} and a laser diode array end-pumping architecture
Beach, R.J.
Wing pumping a Tm{sup 3+} doped, end pumped solid state laser generates 2 {micro}m laser radiation at high average powers with high efficiency. Using laser diode arrays to end-pump the laser rod or slab in the wing of the Tm{sup 3+} absorption band near 785 nm results in 2-for-1 quantum efficiency in Tm{sup 3+} because high Tm{sup 3+} concentrations can be used. Wing pumping allows the thermal power generated in the rod or slab to be distributed over a large enough volume to make thermal management practical in the laser gain medium even at high average power operation. The approach is applicable to CW, Q-switched, and rep-pulsed free-laser operation. 7 figs.
High efficiency 2 micrometer laser utilizing wing-pumped Tm.sup.3+ and a laser diode array end-pumping architecture
Beach, Raymond J. (Livermore, CA)
Wing pumping a Tm.sup.3+ doped, end pumped solid state laser generates 2 .mu.m laser radiation at high average powers with high efficiency. Using laser diode arrays to end-pump the laser rod or slab in the wing of the Tm.sup.3+ absorption band near 785 nm results in 2-for-1 quantum efficiency in Tm.sup.3+ because high Tm.sup.3+ concentrations can be used. Wing pumping allows the thermal power generated in the rod or slab to be distributed over a large enough volume to make thermal management practical in the laser gain medium even at high average power operation. The approach is applicable to CW, Q-switched, and rep-pulsed free-laser operation.
Direct characterization of aqueous extract of Hibiscus sabdariffa using HPLC with diode array detection coupled to ESI and ion trap MS.
RodrĒguez-Medina, Inmaculada C; Beltrßn-Deb¾n, Ra·l; Molina, Vicente Micol; Alonso-Villaverde, Carlos; Joven, Jorge; Menķndez, Javier A; Segura-Carretero, Antonio; Fernßndez-Gutiķrrez, Alberto
The phenolic fraction and other polar compounds of the Hibiscus sabdariffa were separated and identified by HPLC with diode array detection coupled to electrospray TOF and IT tandem MS (DAD-HPLC-ESI-TOF-MS and IT-MS). The H. sabdariffa aqueous extract was filtered and directly injected into the LC system. The analysis of the compounds was carried out by RP HPLC coupled to DAD and TOF-MS in order to obtain molecular formula and exact mass. Posterior analyses with IT-MS were performed and the fragmentation pattern and confirmation of the structures were achieved. The H. sabdariffa samples were successfully analyzed in positive and negative ionization modes with two optimized linear gradients. In positive mode, the two most representative anthocyanins and other compounds were identified whereas the phenolic fraction, hydroxycitric acid and its lactone were identified using the negative ionization mode. PMID:19750503
Simultaneous Detection of Sulfamethoxazole, Diclofenac, Carbamazepine, and Bezafibrate by Solid Phase Extraction and High Performance Liquid Chromatography with Diode Array Detection
NASA Astrophysics Data System (ADS)
Zhou, Z.; Jiang, J.-Q.
A method of solid phase extraction (SPE) coupled with high performance liquid chromatography and diode array detection (HPLC-DAD) was studied for the simultaneous determination of sulfamethoxazole (SMX), diclofenac (DCF), carbamazepine (CBZ), and bezafi brate (BZF) in test solutions. The target compounds were extracted by SPE from samples, and the resulting elutes were analyzed using a HPLC-DAD system at wavelengths of 270, 280, 290, and 230 nm for SMX, DCF, CBZ, and BZF, respectively. This method shows good recoveries for SMX, DCF, CBZ, and BZF with mean recoveries of 89.7 ▒ 9.3%, 86.1 ▒ 7.6%, 95.0 ▒ 6.5%, and 94.0 ▒ 5.4%, respectively.
Analysis by high-performance liquid chromatography diode array detection mass spectrometry of phenolic compounds in fruit of Eucalyptus globulus cultivated in Algeria.
Boulekbache-Makhlouf, Lila; Meudec, Emmanuelle; Chibane, Mohamed; Mazauric, Jean-Paul; Slimani, Sakina; Henry, Max; Cheynier, Veronique; Madani, Khodir
A method based on high-performance liquid chromatography coupled with diode array detection and electrospray ionization mass spectrometry (HPLC-DAD-ESI-MS) following fractionation by chromatography on a Sephadex LH-20 column has been developed to determine the phenolic composition of fruit of Eucalyptus globulus growing in Algeria. The presence of 18 gallotannins, 26 ellagitannins, and 2 flavonols was established. Tentative identification is provided for these compounds on the basis of UV-visible spectra and mass spectrometry data. Most compounds described in this study have not previously detected in fruit of E. globulus. Moreover, this is the first report of methyl digalloyl diglucose, 3,3'-O-dimethylellagic acid 4-O-?-glucopyranoside, ellagic acid hexose, methyl ellagic acid pentose, methyltetragalloylglucose, and valoneic acid isomers (sanguisorbic, flavogallic acid dilactone) in the genus Eucalyptus. Quantitatively, ellagic acid and its derivatives, including ellagitannins, are largely predominant. PMID:21121679
Hard modeling methods for the curve resolution of data from liquid chromatography with a diode array detector and on-flow liquid chromatography with nuclear magnetic resonance spectroscopy.
Wasim, Mohammad; Brereton, Richard G
Hard modeling methods have been performed on data from high-performance liquid chromatography with a diode array detector (LC-DAD) and on-flow liquid chromatography with 1H nuclear magnetic spectroscopy (LC-NMR). Four methods have been used to optimize parameters to model concentration profiles, three of which belong to classical optimization methods (the simplex method of Nelder-Mead, sequential quadratic programming approach, and Levenberg-Marquardt method), and the fourth is the application of genetic algorithms using real-value encoding. Only classical methods worked well for LC-DAD data, while all of the methods produced good results when LC-NMR data were divided into small spectral windows of peak clusters and parameters were optimized over each window. PMID:16711734
Room-temperature violet luminescence and ultraviolet photodetection of Sb-doped ZnO/Al-doped ZnO homojunction array
A Sb-doped ZnO microrod array was fabricated on an Al-doped ZnO thin film by electrodeposition. Strong violet luminescence, originated from free electron-to-acceptor level transitions, was identified by temperature-dependent photoluminescence measurements. This acceptor-related transition was attributed to substitution of Sb dopants for Zn sites, instead of O sites, to form a complex with two Zn vacancies (VZn), the SbZn-2VZn complex. This SbZn-2VZn complex has a lower formation energy and acts as a shallow acceptor which can induce the observed strong violet luminescence. The photoresponsivity of our ZnO p-n homojunction device under a negative bias demonstrated a nearly 40-fold current gain, illustrating that our device is potentially an excellent candidate for photodetector applications in the ultraviolet wavelength region. PMID:23826909
Effects of Mg-doped AlN/AlGaN superlattices on properties of p-GaN contact layer and performance of deep ultraviolet light emitting diodes
Al tahtamouni, T. M., E-mail: email@example.com [Department of Physics, Yarmouk University, Irbid 21163 (Jordan); Lin, J. Y.; Jiang, H. X. [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)] [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)
Mg-doped AlN/AlGaN superlattice (Mg-SL) and Mg-doped AlGaN epilayers have been investigated in the 284 nm deep ultraviolet (DUV) light emitting diodes (LEDs) as electron blocking layers. It was found that the use of Mg-SL improved the material quality of the p-GaN contact layer, as evidenced in the decreased density of surface pits and improved surface morphology and crystalline quality. The performance of the DUV LEDs fabricated using Mg-SL was significantly improved, as manifested by enhanced light intensity and output power, and reduced turn-on voltage. The improved performance is attributed to the enhanced blocking of electron overflow, and enhanced hole injection.
The enhancement of light-emitting efficiency using GaN-based multiple quantum well light-emitting diodes with nanopillar arrays
NASA Astrophysics Data System (ADS)
Wan, Tu-Tu; Ye, Zhan-Qi; Tao, Tao; Xie, Zi-Li; Zhang, Rong; Liu, Bin; Xiu, Xiang-Qian; Li, Yi; Han, Ping; Shi, Yi; Zheng, You-Dou
The quest for higher modulation speed and lower energy consumption has inevitably promoted the rapid development of semiconductor-based solid lighting devices in recent years. GaN-based light-emitting diodes (LEDs) have emerged as promising candidates for achieving high efficiency and high intensity, and have received increasing attention among many researchers in this field. In this paper, we use a self-assembled array-patterned mask to fabricate InGaN/GaN multi-quantum well (MQW) LEDs with the intention of enhancing the light-emitting efficiency. By utilizing inductively coupled plasma etching with a self-assembled Ni cluster as the mask, nanopillar arrays are formed on the surface of the InGaN/GaN MQWs. We then observe the structure of the nanopillars and find that the V-defects on the surface of the conventional structure and the negative effects of threading dislocation are effectively reduced. Simultaneously, we make a comparison of the photoluminescence (PL) spectrum between the conventional structure and the nanopillar arrays, achieved under an experimental set-up with an excitation wavelength of 325 mm. The analysis demonstrates that MQW-LEDs with nanopillar arrays achieve a PL intensity 2.7 times that of conventional LEDs. In response to the PL spectrum, some reasons are proposed for the enhancement in the light-emitting efficiency as follows: 1) the improvement in crystal quality, namely the reduction in V-defects; 2) the roughened surface effect on the expansion of the critical angle and the attenuated total reflection; and 3) the enhancement of the light-extraction efficiency due to forward scattering by surface plasmon polariton modes in Ni particles deposited above the p-type GaN layer at the top of the nanopillars.
Luminescent properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ particles as a potential bluish green phosphor for ultraviolet light-emitting diodes
NASA Astrophysics Data System (ADS)
Yao, Shanshan; Chen, Donghua
In our study, the 1% mol Eu2+ doped Li2CaSiO4: B3+ phosphors were prepared by the combustion method as fluorescent material for ultraviolet, light-emitting diodes (UV-LEDs) used as a light source. The properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ phosphors with urea concentration, doping boric acid and a series of initiating combustion temperature were investigated. The crystallization and particle sizes of Li2 (Ca0.99, Eu0.01) SiO4: B3+ has been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by UV to the visible region, and exhibited bluish green light with a peak of 480 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li2 (Ca0.99, Eu0.01) SiO4: B3+ and the optimum molar ratio of boric acid to calcium nitrate was about 0.06. The optimized phosphors Li2 (Ca0.99, Eu0.01) SiO4: B{0.06/3+} showed 180% improved emission intensity compared with that of the Li2 (Ca0.99, Eu0.01) SiO4 phosphors under ultraviolet (?ex =287 nm) excitation.
Combustion synthesis and luminescent properties of a new material Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ for ultraviolet light emitting diodes
NASA Astrophysics Data System (ADS)
Yao, Shanshan; Chen, Donghua
Using urea as fuel and boric as flux, a novel bluish green emitting phosphor Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ has been successfully synthesized using a combustion method. The material has potential application as the fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). The dependence of the properties of Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ phosphors upon urea concentration, boric acid doping and initiating combustion temperature were investigated. The crystallization and particle sizes of Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ have been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by ultraviolet (UV) to visible region, emitting a bluish green light with peak wavelength of 490 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li 2(Ba 0.99,Eu 0.01)SiO 4 and the optimum molar ratio of boric acid to barium nitrate was about 0.06. The optimized phosphors Li 2(Ba 0.99,Eu 0.01)SiO 4:B 0.063+ showed 160% improved emission intensity compared with that of the Li 2(Ba 0.99,Eu 0.01)SiO 4 phosphors under UV ( ?ex=350 nm) excitation.
Luminescent properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ particles as a potential bluish green phosphor for ultraviolet light-emitting diodes
NASA Astrophysics Data System (ADS)
Yao, Shanshan; Chen, Donghua
In our study, the 1% mol Eu2+ doped Li2CaSiO4: B3+ phosphors were prepared by the combustion method as fluorescent material for ultraviolet, light-emitting diodes (UV-LEDs) used as a light source. The properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ phosphors with urea concentration, doping boric acid and a series of initiating combustion temperature were investigated. The crystallization and particle sizes of Li2 (Ca0.99, Eu0.01) SiO4: B3+ has been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by UV to the visible region, and exhibited bluish green light with a peak of 480 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li2 (Ca0.99, Eu0.01) SiO4: B3+ and the optimum molar ratio of boric acid to calcium nitrate was about 0.06. The optimized phosphors Li2 (Ca0.99, Eu0.01) SiO4: B0.063+ showed 180% improved emission intensity compared with that of the Li2 (Ca0.99, Eu0.01) SiO4 phosphors under ultraviolet (?ex =287 nm) excitation.
Nanospherical-lens lithographical Ag nanodisk arrays embedded in p-GaN for localized surface plasmon-enhanced blue light emitting diodes
NASA Astrophysics Data System (ADS)
Wei, Tongbo; Wu, Kui; Lan, Ding; Sun, Bo; Zhang, Yonghui; Chen, Yu; Huo, Ziqiang; Hu, Qiang; Wang, Junxi; Zeng, Yiping; Li, Jinmin
Large-scale Ag nanodisks (NDs) arrays fabricated using nanospherical-lens lithography (NLL) are embedded in p-GaN layer of an InGaN/GaN light-emitting diode (LED) for generating localized surface plasmon (LSP) coupling with the radiating dipoles in the quantum-well (QWs). Based on the Ag NDs with the controlled surface coverage, LSP leads to the improved crystalline quality of regrowth p-GaN, increased photoluminescence (PL) intensity, reduced PL decay time, and enhanced output power of LED. Compared with the LED without Ag NDs, the optical output power at a current of 350 mA of the LSP-enhanced LEDs with Ag NDs having a distance of 20 and 35 nm to QWs is increased by 26.7% and 31.1%, respectively. The electrical characteristics and optical properties of LEDs with embedded Ag NPs are dependent on the distance of between Ag NPs and QWs region. The LED with Ag NDs array structure is also found to exhibit reduced emission divergence, compared to that without Ag NDs.
Nanospherical-lens lithographical Ag nanodisk arrays embedded in p-GaN for localized surface plasmon-enhanced blue light emitting diodes
Wei, Tongbo, E-mail: firstname.lastname@example.com; Wu, Kui; Sun, Bo; Zhang, Yonghui; Chen, Yu; Huo, Ziqiang; Hu, Qiang; Wang, Junxi; Zeng, Yiping; Li, Jinmin [State Key Laboratory of Solid-State Lighting, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083 (China); Lan, Ding [National Microgravity Laboratory, Institute of Mechanics, Chinese Academy of Sciences, Beijing, 100080 (China)
Large-scale Ag nanodisks (NDs) arrays fabricated using nanospherical-lens lithography (NLL) are embedded in p-GaN layer of an InGaN/GaN light-emitting diode (LED) for generating localized surface plasmon (LSP) coupling with the radiating dipoles in the quantum-well (QWs). Based on the Ag NDs with the controlled surface coverage, LSP leads to the improved crystalline quality of regrowth p-GaN, increased photoluminescence (PL) intensity, reduced PL decay time, and enhanced output power of LED. Compared with the LED without Ag NDs, the optical output power at a current of 350 mA of the LSP-enhanced LEDs with Ag NDs having a distance of 20 and 35 nm to QWs is increased by 26.7% and 31.1%, respectively. The electrical characteristics and optical properties of LEDs with embedded Ag NPs are dependent on the distance of between Ag NPs and QWs region. The LED with Ag NDs array structure is also found to exhibit reduced emission divergence, compared to that without Ag NDs.
INVITED PAPER: III-nitride micro-emitter arrays: development and applications
NASA Astrophysics Data System (ADS)
Fan, Z. Y.; Lin, J. Y.; Jiang, H. X.
III-nitride micro-emitter array technology was developed in the authors' laboratory around 1999. Since its inception, much progress has been made by several groups and the technology has led to the invention of several novel devices. This paper provides an overview on recent progress in single-chip ac-micro-size light emitting diodes (?LEDs) that can be plugged directly into standard high ac voltage power outlets, self-emissive microdisplays and interconnected ?LEDs for boosting light emitting diodes's wall-plug efficiency, all of which were evolved from III-nitride micro-emitter array technology. Finally, potential applications of III-nitride visible micro-emitter arrays as a light source for DNA microarrays and future prospects of III-nitride deep ultraviolet micro-emitter arrays for label-free protein analysis in microarray format by taking advantage of the direct excitation of intrinsic protein fluorescence are discussed.
Internal quantum efficiency of highly-efficient InxGa1-xN-based near-ultraviolet light-emitting diodes
Satoshi Watanabe; Norihide Yamada; Masakazu Nagashima; Yusuke Ueki; Chiharu Sasaki; Yoichi Yamada; Tsunemasa Taguchi; Kazuyuki Tadatomo; Hiroaki Okagawa; Hiromitsu Kudo
The internal quantum efficiency (IQE) of highly-efficient near-UV light-emitting diodes, which shows an external quantum efficiency of 43% at 406 nm, has been measured by excitation power and temperature-dependent photoluminescence (PL). Assuming peak PL quantum efficiency at 8 K is 100%, peak IQE at 300 K was measured to be as high as 63%. At the injected carrier density, which
The wavelength beam-combining fiber-coupled diode laser is the first
The wavelength beam-combining fiber-coupled diode laser is the first direct-diode laser that is bright enough to cut and weld metal. Although diode lasers are the highest efficiency lasers, until of fiber-coupled diode lasers is the diode-laser bar. A diode- laser bar typically consists of an array (e
A novel automated hydrophilic interaction liquid chromatography method using diode-array detector/electrospray ionization tandem mass spectrometry for analysis of sodium risedronate and related degradation products in pharmaceuticals.
Bertolini, Tiziana; Vicentini, Lorenza; Boschetti, Silvia; Andreatta, Paolo; Gatti, Rita
A simple, sensitive and fast hydrophilic interaction liquid chromatography (HILIC) method using ultraviolet diode-array detector (UV-DAD)/electrospray ionization tandem mass spectrometry was developed for the automated high performance liquid chromatography (HPLC) determination of sodium risedronate (SR) and its degradation products in new pharmaceuticals. The chromatographic separations were performed on Ascentis Express HILIC 2.7?m (150mmū2.1mm, i.d.) stainless steel column (fused core). The mobile phase consisted of formate buffer solution (pH 3.4; 0.03M)/acetonitrile 42:58 and 45:55 (v/v) for granules for oral solution and effervescent tablet analysis, respectively, at a flow-rate of 0.2mL/min, setting the wavelength at 262nm. Stability characteristics of SR were evaluated by performing stress test studies. The main degradation product formed under oxidation conditions corresponding to sodium hydrogen (1-hydroxy-2-(1-oxidopyridin-3-yl)-1-phosphonoethyl)phosphonate was characterized by high performance liquid chromatography-electrospray ionization-mass tandem mass spectrometry (HPLC-ESI-MS/MS). The validation parameters such as linearity, sensitivity, accuracy, precision and selectivity were found to be highly satisfactory. Linear responses were observed in standard and in fortified placebo solutions. Intra-day precision (relative standard deviation, RSD) was ?1.1% for peak area and ?0.2% for retention times (tR) without significant differences between intra- and inter-day data. Recovery studies showed good results for all the examined compounds (from 98.7 to 101.0%) with RSD ranging from 0.6 to 0.7%. The limits of detection (LOD) and quantitation (LOQ) were 1 and 3ng/mL, respectively. The high stability of standard and sample solutions at room temperature means an undoubted advantage of the method allowing the simultaneous preparation of many samples and consecutive chromatographic analyses by using an autosampler. The developed stability indicating method is suitable for the quality control of SR in new and commercial pharmaceutical formulations. PMID:25242223
Determination of organophosphorus pesticides in bovine tissue by an on-line coupled matrix solid-phase dispersion¢solid phase extraction¢high performance liquid chromatography with diode array detection method
Tania M. Gutiķrrez Valencia; Martha P. GarcĒa de Llasera
A miniaturized method based on matrix solid-phase dispersion coupled to solid phase extraction and high performance liquid chromatography with diode array detection (MSPD¢SPE¢HPLC\\/DAD) was developed for the trace simultaneous determination of the following organophosphorus pesticides (OPPs) in bovine tissue: parathion-methyl, fenitrothion, parathion, chlorfenvinphos, diazinon, ethion, fenchlorphos, chlorpyrifos and carbophenothion. To perform the coupling between MSPD and SPE, 0.05g of sample
Simultaneous determination of in total 17 opium alkaloids and opioids in blood and urine by fast liquid chromatography¢diode-array detection¢fluorescence detection, after solid-phase extraction
R Dams; T Benijts; W. E Lambert; A. P De Leenheer
A fast liquid chromatographic method with tandem diode array¢fluorescence detection for the simultaneous determination of in total 17 opium alkaloids and opioids is presented. Blank blood and urine samples (1 ml) were spiked with different concentrations of a standard mixture, as well as with the internal standard, butorphanol (2000 ng\\/ml). After solid-phase extraction, based on weak cation exchange (Bond Elut«
Structural elucidation of catechin and epicatechin in sorrel leaf extracts using liquid-chromatography coupled to diode array-, fluorescence-, and mass spectrometric detection.
St÷ggl, W M; Huck, C W; Bonn, G³nther K
Flavonoids are natural compounds in medicinal herbs and posses several biological activities important in plant drug design. Especially strong antioxidant effects play an important role against radical oxidative stress causing pathological processes, such as arteriosclerosis or cancer. The aim of this work was to investigate unknown analytes found in sorrel leaf (Rumex acetosa) extracts in order to discover new leading compounds to enable quality control in phytopharmaceuticals made thereof. Therefore compounds of interest were separated after methanolic extraction by reversed-phase liquid chromatography (RP-LC) employing silica-C18 as stationary phase using gradient elution with water (10 mM H3PO4) and acetonitrile as mobile phase. Structural elucidation was carried out by diode array, fluorescence, and mass spectroscopic detection. Photodiode-array detection allowed the extraction of UV-absorbance spectra from the peaks of interest. Absorbance maxima were found at 203 and 279 nm with a shoulder at 230 nm. Additionally fluorescence emission and excitation spectra were recorded from the analytes using a fluorescence detector (FLD) after stop flow (lambdaex = 279 nm, lambdaem = 307 nm). The chromatographic reversed-phase system was coupled to an ion-trap mass spectrometer (LC-MS) by using an electrospray ionization interface (ESI). After optimization processes the separation was carried out using an ammonium acetate buffer at pH 5.5. Mass spectrometric detection turned out to be more sensitive in negative mode. Collisionally induced dissociation (CID) was used to obtain fragment ions of structural relevance (LC-MS/MS). Finally, compounds of interest coming from sorrel leaf (Rumex acetosa) eluting at low acetonitrile concentrations were confirmed to be catechin and epicatechin. PMID:15335034
Wavelength error analysis in a multiple-beam Fizeau laser wavemeter having a linear diode array readout
NASA Technical Reports Server (NTRS)
Robinson, D. M.; Fales, C. L., Jr.; Skolaut, M. W., Jr.
An estimate of the wavelength accuracy of a laser wavemeter is performed for a system consisting of a multiple-beam Fizeau interferometer and a linear photosensor array readout. The analysis consists of determining the fringe position errors which result when various noise sources are included in the fringe forming and detection process. Two methods of estimating the fringe centers are considered: (1) maximum pixel current location, and (2) average pixel location for two detectors with nearly equal output currents. Wavelength error results for these two methods are compared for some typical wavemeter parameters.
Ionic liquids for improving the extraction of NSAIDs in water samples using dispersive liquid-liquid microextraction by high performance liquid chromatography-diode array-fluorescence detection.
Toledo-Neira, Carla; ┴lvarez-Lueje, Alejandro
A rapid, sensitive and efficient analytical method based on the use of ionic liquids for determination of non-steroidal anti-inflammatory drugs (NSAIDs) in water samples was developed. High-performance liquid chromatography equipped with a diode array and fluorescence detector was used for quantification of ketoprofen, ibuprofen and diclofenac in tap and river water samples. This new method relies on the use of two ionic liquids with multiple functionalities: one functions as an extraction solvent (1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and the other changes the polarity in the aqueous medium (1-butyl-3-methylimidazolium tetrafluoroborate, ([BMIM][BF4]). Factors such as the type and volume of the ILs and dispersive solvent, sample volume, and centrifugation time were investigated and optimized. The optimized method exhibited good precision, with relative standard deviation values between 2% and 3%, for the three NSAIDs. Limits of detection achieved for all of the analytes were between 17 and 95 ng mL(-1), and the recoveries ranged from 89% to 103%. Furthermore, the enrichment factors ranged from 49 to 57. The proposed method was successfully applied to the analysis of NSAIDs in tap and river water samples. PMID:25618715
Comparative study of Puerariae lobatae and Puerariae thomsonii by HPLC-diode array detection-flow injection-chemiluminescence coupled with HPLC-electrospray ionization-MS.
Zhang, Cui-Ling; Ding, Xiao-Ping; Hu, Zheng-Fang; Wang, Xin-Tang; Chen, Lin-Lin; Qi, Jin; Yu, Bo-Yang
An on-line HPLC-diode array detection-flow injection chemiluminescence (HPLC-DAD-FICL) method was applied to estimate the difference of Puerariae lobatae and Puerariae thomsonii. Their chemical and active profiles could be obtained by HPLC-DAD-FICL in one run. Seventeen compounds in two species were tentatively identified by HPLC-electrospray ionization-MS (HPLC-ESI-MS) method. The main antioxidants were rapidly screened by active fingerprints coupled with MS data. Similarity and Hierarchical clustering analysis (HCA) were used to distinguish different samples. The results suggested that the chemical fingerprints of 16 batches of samples were similar by similarity evaluation, while HCA could discriminate the two species. The active fingerprints of Puerariae lobatae and Puerariae thomsonii were significantly different. More antioxidants were found in Puerariae lobatae than in Puerariae thomsonii. Main antioxidants, including 3'-hydroxypuerarin, genistein 8-C-glycoside-xyloside, puerarin, 6?-O-xylosylpuerarin, mirificin and daidzein in two species, may be reasonable markers for the discrimination of the two species. The integrated fingerprint based on the chemical and active characteristics may provide an objective quality evaluation for Puerariae lobatae and Puerariae thomsonii. PMID:21532189
Direct identification of phenolic constituents in Boldo Folium (Peumus boldus Mol.) infusions by high-performance liquid chromatography with diode array detection and electrospray ionization tandem mass spectrometry.
Simirgiotis, M J; Schmeda-Hirschmann, G
A very simple and direct method was developed for the qualitative analysis of polyphenols in boldo (Peumus boldus Mol., Monimiaceae) leaves infusions by high-performance liquid chromatography with diode array detection (HPLC-DAD) and electrospray ionization tandem mass spectrometry (HPLC-MS(n)). The phenolic constituents identified in infusions of the crude drug Boldo Folium were mainly proanthocyanidins and flavonol glycosides. In the infusions, 41 compounds were detected in male and 43 compounds in female leaf samples, respectively. Nine quercetin glycosides, eight kaempferol derivatives, nine isorhamnetin glycosides, three phenolic acids, one caffeoylquinic acid glycoside and twenty one proanthocyanidins were identified by HPLC-DAD and ESI-MS for the first time in the crude drug. Isorhamnetin glucosyl-di-rhamnoside was the most abundant flavonol glycoside in the male boldo sample, whereas isorhamnetin di-glucosyl-di-rhamnoside was the main phenolic compound in female boldo leaves infusion. The results suggest that the medicinal properties reported for this popular infusion should be attributed not only to the presence of catechin and boldine but also to several phenolic compounds with known antioxidant activity. The HPLC fingerprint obtained can be useful in the authentication of the crude drug Boldo Folium as well as for qualitative analysis and differentiation of plant populations in the tree distribution range. PMID:20022332
Three-dimensional mesoscale heterostructures of ZnO nanowire arrays epitaxially grown on CuGaO2 nanoplates as individual diodes.
Forticaux, Audrey; Hacialioglu, Salih; DeGrave, John P; Dziedzic, Rafal; Jin, Song
We report a three-dimensional (3D) mesoscale heterostructure composed of one-dimensional (1D) nanowire (NW) arrays epitaxially grown on two-dimensional (2D) nanoplates. Specifically, three facile syntheses are developed to assemble vertical ZnO NWs on CuGaO2 (CGO) nanoplates in mild aqueous solution conditions. The key to the successful 3D mesoscale integration is the preferential nucleation and heteroepitaxial growth of ZnO NWs on the CGO nanoplates. Using transmission electron microscopy, heteroepitaxy was found between the basal planes of CGO nanoplates and ZnO NWs, which are their respective (001) crystallographic planes, by the observation of a hexagonal Moirķ fringes pattern resulting from the slight mismatch between the c planes of ZnO and CGO. Careful analysis shows that this pattern can be described by a hexagonal supercell with a lattice parameter of almost exactly 11 and 12 times the a lattice constants for ZnO and CGO, respectively. The electrical properties of the individual CGO-ZnO mesoscale heterostructures were measured using a current-sensing atomic force microscopy setup to confirm the rectifying p-n diode behavior expected from the band alignment of p-type CGO and n-type ZnO wide band gap semiconductors. These 3D mesoscale heterostructures represent a new motif in nanoassembly for the integration of nanomaterials into functional devices with potential applications in electronics, photonics, and energy. PMID:23952783
New method for the quantification of dequalinium cations in pharmaceutical samples by absorption and fluorescence diode array thin-layer chromatography.
Hiegel, Katharina; Spangenberg, Bernd
A diode array HPTLC method for dequalinium chloride in pharmaceutical preparations is presented. For separation a Nano TLC silica gel plate (Merck) is used with the mobile phase methanol-7.8% aqueous NH(4)(+)CH(3)COO(-) (17:3, v/v) over a distance of 6 cm. Dequalinium chloride shows an R(F) value of 0.58. Pure dequalinium chloride is measured in the wavelength range from 200 to 500 nm and shows several by-products, contour plot visualized in absorption, fluorescence and using the Kubelka-Munk transformation. Scanning of a single track in absorption and fluorescence measuring 600 spectra in the range from 200 to 1100 nm takes 30s. As a sample pre-treatment of an ointment it is simply dissolved in methanol and can be quantified in absorption from 315 to 340 nm. The same separation can also be quantified using fluorescence spectrometry in the range from 355 to 370 nm. A new staining method for dequalinium chloride, using sodium tetraphenyl borate/HCl in water allows a fluorescence quantification in the range from 445 to 485 nm. The linearity range of absorption and fluorescence measurements is from 10 to 2000 ng. Sugar-containing preparations like liquids or lozenges with a reduced sample pre-treatment can be reliably quantified only in fluorescence. The total for the quantification of an ointment sample (measuring four standards and five samples), including all sample pre-treatment steps takes less than 45 min! PMID:19446824
Analysis of alkylamides in Echinacea plant materials and dietary supplements by ultrafast liquid chromatography with diode array and mass spectrometric detection.
Mudge, Elizabeth; Lopes-Lutz, Daise; Brown, Paula; Schieber, Andreas
Alkylamides are a class of compounds present in plants of the genus Echinacea (Asteraceae), which have been shown to have high bioavailability and immunomodulatory effects. Fast analysis to identify these components in a variety of products is essential to profile products used in clinical trials and for quality control of these products. A method based on ultrafast liquid chromatography (UFLC) coupled with diode array detection and electrospray ionization mass spectrometry was developed for the analysis of alkylamides from the roots of Echinacea angustifolia (DC.) Hell., Echinacea purpurea (L.) Moench, and commercial dietary supplements. A total of 24 alkylamides were identified by LC-MS. The analysis time for these components is 15 min. Compared to the alkylamide profiles determined in the Echinacea root materials, the commercial products showed a more complex profile due to the blending of root and aerial parts of E. purpurea. This versatile method allows for the identification of alkylamides in a variety of Echinacea products and presents the most extensive characterization of alkylamides in E. angustifolia roots so far. PMID:21702479
Analytical method development for the determination of emerging contaminants in water using supercritical-fluid chromatography coupled with diode-array detection.
Del Carmen Salvatierra-Stamp, Vilma; Ceballos-Maga±a, Silvia G; Gonzalez, Jorge; Ibarra-Galvßn, Valentin; Mu±iz-Valencia, Roberto
An analytical method using supercritical-fluid chromatography coupled with diode-array detection for the determination of seven emerging contaminants-two pharmaceuticals (carbamazepine and glyburide), three endocrine disruptors (17?-ethinyl estradiol, bisphenol A, and 17?-estradiol), one bactericide (triclosan), and one pesticide (diuron)-was developed and validated. These contaminants were chosen because of their frequency of use and their toxic effects on both humans and the environment. The optimized chromatographic separation on a Viridis BEH 2-EP column achieved baseline resolution for all compounds in less than 10 min. This separation was applied to environmental water samples after sample preparation. The optimized sample treatment involved a preconcentration step by means of solid-phase extraction using C18-OH cartridges. The proposed method was validated, finding recoveries higher than 94 % and limits of detection and limits of quantification in the range of 0.10-1.59 ?g L(-1) and 0.31-4.83 ?g L(-1), respectively. Method validation established the proposed method to be selective, linear, accurate, and precise. Finally, the method was successfully applied to environmental water samples. PMID:25801381
Chemical analysis of raw and processed Fructus arctii by high-performance liquid chromatography/diode array detection-electrospray ionization-mass spectrometry
Qin, Kunming; Liu, Qidi; Cai, Hao; Cao, Gang; Lu, Tulin; Shen, Baojia; Shu, Yachun; Cai, Baochang
Background: In traditional Chinese medicine (TCM), raw and processed herbs are used to treat the different diseases. Fructus Arctii, the dried fruits of Arctium lappa l. (Compositae), is widely used in the TCM. Stir-frying is the most common processing method, which might modify the chemical compositions in Fructus Arctii. Materials and Methods: To test this hypothesis, we focused on analysis and identification of the main chemical constituents in raw and processed Fructus Arctii (PFA) by high-performance liquid chromatography/diode array detection-electrospray ionization-mass spectrometry. Results: The results indicated that there was less arctiin in stir-fried materials than in raw materials. however, there were higher levels of arctigenin in stir-fried materials than in raw materials. Conclusion: We suggest that arctiin reduced significantly following the thermal conversion of arctiin to arctigenin. In conclusion, this finding may shed some light on understanding the differences in the therapeutic values of raw versus PFA in TCM. PMID:25422559
The identification of related substances in triamcinolone acetonide by means of high-performance liquid chromatography with diode array detector and mass spectrometry.
Cavina, G; Alimenti, R; Gallinella, B; Valvo, L
A study of an HPLC method for the analysis of related substances in triamcinolone acetonide is described. Several systems of solvents and samples of different lots and preparative origins were examined and a rapid-scanning diode array UV detector (DAD) was particularly useful. With the proposed technique it was possible to identify 9 alpha-bromo desonide as a principal impurity, which was present in all examined samples of triamcinolone acetonide. This identification was rendered possible by the investigation of the second derivative of the UV spectra and by means of study of the mass spectrum. Furthermore, it was possible, primarily on the basis of the spectrophotometric data, to formulate reliable hypotheses on the possible identification of 9 beta, 11 beta-epoxide of the desonide which was present at very low levels and to exclude the presence of 11-deoxy-9(11)-unsaturated desonide. The presence of the above-mentioned related substances was explained considering the scheme of synthesis described in the literature. The spectrophotometric characteristics of the studied compounds and the limits of applicability of the present procedure are discussed. PMID:1286133
Quantitative analysis of the eight major compounds in the Samsoeum using a high-performance liquid chromatography coupled with diode array detection and electrospray ionization mass spectrometer
Weon, Jin Bae; Yang, Hye Jin; Lee, Bohyoung; Ma, Jin Yeul; Ma, Choong Je
Background: Samsoeum was traditionally used for treatment of a respiratory disease. Objective: The simultaneous determination of eight major compounds, ginsenoside Rg3, caffeic acid, puerarin, costunolide, hesperidin, naringin, glycyrrhizin, and 6-gingerol in the Samsoeum using a high-performance liquid chromatography (HPLC) coupled with diode array detection (DAD) and an electrospray ionization mass spectrometer was developed for an accurate and reliable quality assessment. Materials and Methods: Eight compounds were qualitative identified based on their mass spectra and by comparing with standard compounds and quantitative analyzed by HPLC-DAD. Separation of eight compounds was carried out on a LUNA C18 column (S-5 ?m, 4.6 mm i.d. ū250 mm) with gradient elution composed of acetonitrile and 0.1% trifluoroacetic acid. Results: The data showed good linearity (R2 > 0.9996). The limits of detection and the limits of quantification were <0.53 ?g and 1.62 ?g, respectively. Inter- and Intra-day precisions (expressed as relative standard deviation values) were within 1.94% and 1.91%, respectively. The recovery of the method was in the range of 94.24¢107.90%. Conclusion: The established method is effective and could be applied to quality control of Samsoeum. PMID:25829771
Headspace in-drop derivatization of carbonyl compounds for their analysis by high-performance liquid chromatography-diode array detection.
Pillai, Aradhana K K V; Gautam, Khileshwari; Jain, Archana; Verma, Krishna K
A simple and rapid method has been reported for the determination of carbonyl compounds involving sample preparation by headspace single drop microextraction using 1-butanol as extraction solvent containing 2,4-dinitrophenylhydrazine for hydrazone formation, and direct transfer of the drop into the injector for high-performance liquid chromatography with diode array detection. An angle-cut polytetrafluoroethylene sleeve, 3mm x 0.5mm, was fixed at the tip of the syringe needle and this allowed the use of 7 microL drop of solvent drop for extraction and derivatization. The procedure has been optimized with respect to suitable solvent for headspace drop formation, drop volume, concentration of reagent, sample temperature, reaction time, and headspace-to-sample volume ratio. The method has been validated when rectilinear relationship was obtained between the amount of analyte and peak area ratio of hydrazones in the range 0.01-15 mg L(-1), the correlation coefficient over 0.996-0.999, and the limit of detection in the range 1.7-24.1 microg L(-1). Spiked real samples have been analyzed with adequate accuracy, and application has been demonstrated of the method for analysis of carbonyl compounds formed as oxidation products. PMID:19110095
Dispersive liquid-liquid microextraction followed by high-performance liquid chromatography-diode array detection as an efficient and sensitive technique for determination of antioxidants.
Farajzadeh, Mir Ali; Bahram, Morteza; J÷nsson, Jan Ake
Dispersive liquid-liquid microextraction (DLLME) and high performance liquid chromatography-diode array detection (HPLC-DAD) was presented for extraction and determination of Irganox 1010, Irganox 1076 and Irgafos 168 (antioxidants) in aqueous samples. Carbon tetrachloride at microliter volume level and acetonitrile were used as extraction and dispersive solvents, respectively. The main advantages of method are high speed, high enrichment factor, high recovery, good repeatability and extraction solvent volume at microL level. Limit of detection for analytes is between 3 and 7 ng mL(-1). One variable at a time optimization and response surface modeling were used to obtain optimum conditions for microextraction procedure and nearly same experimental conditions were obtained using both optimization methods. Recoveries in the ranges 78-86% and 84-110% were obtained by one variable at a time and response surface modeling, respectively. Using tap water and packed water as matrices do not show any detrimental effect on the extraction recoveries and enrichment factors of analytes. PMID:17456426
Screening of seized emerging drugs by ultra-high performance liquid chromatography with photodiode array ultraviolet and mass spectrometric detection.
Li, Li; Lurie, Ira S
The use of psychoactive "designer drugs" has increased rapidly due to their varying and sometimes ambiguous legal status and their ready access via the Internet and at local "headshops." A quick screening method for samples containing these substances, using ultra-high performance liquid chromatography with photodiode array UV and mass spectrometric detection (UHPLC-PDA/UV-MS), is presented. The method enables the screening of a variety of samples containing emerging/reemerging drugs, including ?-keto phenethylamines (cathinone derivatives), synthetic cannabinoids/cannabimimetics, and phenethylamine derivatives. The use of dual detectors not only provides molecular weight information but also differentiates the drugs by their categories and in some cases even their sub-categories. Moreover, ring positional isomers of cathinone and phenethylamine derivatives can be easily differentiated by their retention times and UV spectra. PMID:24607709
Intense violet-blue-emitting Ba(2)AlB(4)O(9)Cl:Eu(2+) phosphors for applications in fluorescent lamps and ultraviolet-light-emitting diodes.
Kuo, Te-Wen; Huang, Chien-Hao; Chen, Teng-Ming
We synthesized a violet-blue phosphor Ba(2)AlB(4)O(9)Cl:Eu(2+) with a solid-state reaction. The excitation and emission spectra of this phosphor showed that all were broadband due to 4f(7)-4f(6)d(1) transitions of Eu(2+). The phosphors with different Eu(2+) concentrations presented violet-blue luminescence for ultraviolet [(UV) 250-390nm] excitation. The optimum concentration of Eu(2+) in Ba(2)AlB(4)O(9)Cl:Eu(2+) is determined to be 6mol.%. The luminous efficiency was found to be 8.1lm/W for the violet-blue fluorescent lamp and 3.2lm/W for the violet-blue phosphor-converted light-emitting diode, respectively. Ba(2)AlB(4)O(9)Cl:Eu(2+) would be a promising phosphor for converting the UV radiation to violet-blue emission for a novel high light-conversion efficiency phototherapy illuminator. PMID:20676174
An enhanced multiwavelength ultraviolet biological trigger lidar
NASA Astrophysics Data System (ADS)
Achey, Alexander; Bufton, Jack; Dawson, Jeffrey; Huang, Wen; Lee, Sangmin; Mehta, Nikhil; Prasad, Coorg R.
A compact Ultraviolet Biological Trigger Lidar (UBTL) instrument for detection and discrimination of bio-warfare-agent (BWA) simulant aerosol clouds was developed by us [Prasad, et al, 2004] using a 5mW, 375nm semiconductor UV optical source (SUVOS) laser diode. It underwent successful field tests at Dugway Proving Ground and demonstrated measurement ranges of over 300m for elastic scattering and >100m for fluorescence. The UBTL was modified during mid-2004 to enhance its detection and discrimination performance with increased range of operation and sensitivity. The major optical modifications were: 1. increase in telescope collection aperture to 200 mm diameter: 2. addition of 266nm and 977nm laser transmitters: 3. addition of three detection channels for 266nm and 977nm elastic backscatter and fluorescence centered at 330nm. Also the commercial electronics of the original UBTL were replaced with a multi-channel field programmable gate array (FPGA) chip for laser diode modulation and data acquisition that allowed simultaneous and continuous operation of the UBTL sensor on all of its transmitter and receiver wavelengths. A notebook computer was added for data display and storage. Field tests were performed during July 2004 at the Edgewood Chemical and Biological Center in Maryland to establish the enhanced performance of UBTL subsystems. Results of these tests are presented and discussed.
Quantitative Analysis of the Head Scatter and Jaw Transmission Correction Factor for Commissioning of Enhanced Dynamic Wedge Fields Using a MapCHECK 2 Diode Array
NASA Astrophysics Data System (ADS)
Dickerson, Edward C.
Quality assurance in radiation oncology treatment planning requires independent verification of dose to be delivered to a patient through "second check" calculations for simple plans as well as planar dose fluence measurements for more complex treatments, such as intensity modulated radiation treatments (IMRT). Discrepancies between treatment planning system (TPS) and second check calculations created a need for treatment plan verification using a two dimensional diode array for Enhanced Dynamic Wedge (EDW) fields. While these measurements met clinical standards for treatment, they revealed room for improvement in the EDW model. The purpose of this study is to analyze the head scatter and jaw transmission effects of the moving jaw in EDW fields by measuring dose profiles with a two dimensional diode array in order to minimize differences between the manufacturer provided fluence table (Golden Segmented Treatment Table) and actual machine output. The jaw transmission effect reduces the dose gradient in the wedge direction due to transmission photons adding dose to the heel region of the field. The head scatter effect also reduces the gradient in the dose profile due to decreased accelerator output at increasingly smaller field sizes caused by the moving jaw. The field size continuously decreases with jaw motion, and thus the toe region of the wedge receives less dose than anticipated due to less head scatter contribution for small field sizes. The Golden Segmented Treatment Table (GSTT) does not take these factors into account since they are specific to each individual machine. Thus, these factors need to be accounted for in the TPS to accurately model the gradient of the wedge. The TPS used in this clinic uses one correction factor (transmission factor) to account for both effects since both factors reduce the dose gradient of the wedge. Dose profile measurements were made for 5x5 cm2, 10x10 cm2, and 20x20 cm2 field sizes with open fields and 10░, 15░, 20░, 25░, 30░, 45░, and 60░ wedges for 6 MV and 18 MV beams and compared with TPS generated profiles. The transmission factor was adjusted for the 18 MV beam to obtain a better correlation between planned and measured dose gradient by reducing the gradient of the wedge in the TPS. This correction resulted in an average and maximum pass rate improvement for patient plans at a distance to agreement of 3% 3mm of 1.07% and 3.9% respectively. The off axis ratio data in the second check calculation software was also adjusted to bring the dose agreement between the initial TPS calculation and second check calculation within clinical standards. This study demonstrated the ability to adjust the EDW gradient in a treatment planning system to improve the differences in machine output specific to each machine and the manufacturer provided GSTT.
Diode-pumped continuous-wave and femtosecond Cr:LiCAF lasers with high average power in the near infrared, visible and near ultraviolet.
Demirbas, Umit; Baali, Ilyes; Acar, Durmus Alp Emre; Leitenstorfer, Alfred
We demonstrate continuous-wave (cw), cw frequency-doubled, cw mode-locked and Q-switched mode-locked operation of multimode diode-pumped Cr:LiCAF lasers with record average powers. Up to 2.54 W of cw output is obtained around 805 nm at an absorbed pump power of 5.5 W. Using intracavity frequency doubling with a BBO crystal, 0.9 W are generated around 402 nm, corresponding to an optical-to-optical conversion efficiency of 12%. With an intracavity birefringent tuning plate, the fundamental and frequency-doubled laser output is tuned continuously in a broad wavelength range from 745 nm to 885 nm and from 375 to 440 nm, respectively. A saturable Bragg reflector is used to initiate and sustain mode locking. In the cw mode-locked regime, the Cr:LiCAF laser produces 105-fs long pulses near 810 nm with an average power of 0.75 W. The repetition rate is 96.4 MHz, resulting in pulse energies of 7.7 nJ and peak powers of 65 kW. In Q-switched mode-locked operation, pulses with energies above 150 nJ are generated. PMID:25968727
Emissive Liquid-Crystal Display Panels Consisting of Red-Green-Blue Patterned Phosphor Layers and Near-Ultraviolet Light-Emitting-Diode Backlight
NASA Astrophysics Data System (ADS)
Yata, Tatsuya; Miyamoto, Yoshinobu; Ohmi, Koutoku
Emissive liquid crystal display (e-LCD) panels consisting of 405 nm near-UV light-emitting-diode (LED) backlight and patterned red-green-blue phosphor layers have been proposed. Improvements in luminous efficiency and lifetime have been systematically attempted. From the results of the accelerated aging test under near-UV irradiation under high temperature and humidity conditions, it has been confirmed that the e-LCD panel has a sufficiently long lifetime for practical use. The light conversion efficiency of the phosphor layer has been significantly improved by using optical filters. Commission Internationale de l'Eclairage (CIE) color coordinates are (0.69, 0.31) for red, (0.27, 0.68) for green and (0.15, 0.04) for blue sub-pixels. The corresponding color gamut is over 100% compared with that of the National Television System Committee. The e-LCD panel also has a considerable wide-viewing-angle property, and its overall luminous efficiency is more than twice higher than those of conventional LCD panels consisting of white-LED and color filters.
Optimization of a liquid chromatography method based on simultaneous electrospray ionization mass spectrometric and ultraviolet photodiode array detection for analysis of flavonoid glycosides.
Cuyckens, Filip; Claeys, Magda
Different reversed-phase liquid chromatography (LC) columns of conventional dimensions were coupled to an ultraviolet photodiode array detector (UV-DAD) and a magnetic sector-type spectrometer, equipped with an electrospray ionization (ESI) source, by a laboratory-made flow splitter. A mixture of three flavonoid-O-glycosides was employed to examine the effects of the solvent composition, the flow rate, the stationary phase, the pH and the organic acid added, on the chromatographic separation, the UV-DAD detection, the ESI process and the entire LC system with ESI-MS and UV-DAD detection. In the positive ion mode, methanol containing 1% acetic acid was by far the most sensitive in ESI-MS analysis, whereas an acetonitrile/water mobile phase containing 0.5% formic acid was proved to give the best sensitivity in LC/ESI-MS/UV-DAD analysis. In the negative ion mode, the highest sensitivity was obtained with a mobile phase containing 0.1% formic acid, while addition of bases decreased the sensititvity. The optimal flow rate was higher in negative ESI (20-50 micro L/min) than in positive ESI (5 micro L/min), and the percentage of organic phase had an influence on the sensitivity of ESI-MS detection. With regard to the selection of a suitable C(18) reversed-phase LC column, a column which is well end-capped is to be preferred, because residual silanol groups appear to impair the separation of flavonoid glycosides. The optimized LC/ESI-MS/UV-DAD method was applied to a commercial Crataegus extract, which is used in phytomedicine to treat cardiovascular problems and is known to be rich in flavonoids. It is demonstrated how UV spectra and first-order ESI mass spectra allow a fast characterization of flavonoids, even if reference compounds are not available or at hand. PMID:12478580
The simultaneous determination of coumarins in Angelica gigas root by high performance liquid chromatography-diode array detector coupled with electrospray ionization/mass spectrometry.
Ahn, Mi-Jeong; Lee, Mi Kyeong; Kim, Young Choong; Sung, Sang Hyun
An high performance liquid chromatography-diode array detector coupled with electrospray ionization/mass spectrometry (HPLC-DAD/MS) based method has been developed for the simultaneous determination of nine coumarin compounds, nodakenin (1), peucedanone (2), marmesin (3), decursinol (4), 7-hydroxy-6-(2R-hydroxy-3-methylbut-3-enyl)coumarin (5), demethylsuberosin (6), decursin (7), decursinol angelate (8) and isoimperatorin (9) in the Korean medicinal herb, Cham-Dang-Gui, the dried root of Angelica gigas (Umbelliferae). The methanol extracts were analyzed by HPLC using a reversed-phase C18 column (5 microm, 4.5 mm x 250 mm) using a gradient acetonitrile-water solvent system at a flow rate of 1.0 ml/min. The analysis of six coumarins (1, 3, 4 and 6-8) with DAD was done at 330 nm and showed excellent linearity (r(2)=0.998-0.999) in a range of 0.2-250 microg/ml for all the compounds. The average recoveries (n=3) were between 96.5% and 110.8%. Identification of each peak was also discussed with the electrospray ionization multi-stage tandem mass spectroscopy (ESI-MS(n)). The amount of these coumarin compounds was evaluated in A. gigas samples. Meanwhile, three coumarins (2, 5 and 9) could not been quantified by DAD because these peaks were overlapped with others. Determination of these compounds could be successfully accomplished with the HPLC-ESI/MS in selected ion monitoring/selected reaction monitoring mode. PMID:17997069
Determination of chlorophylls in Taraxacum formosanum by high-performance liquid chromatography-diode array detection-mass spectrometry and preparation by column chromatography.
Loh, Chin Hoe; Inbaraj, Baskaran Stephen; Liu, Man Hai; Chen, Bing Huei
Taraxacum formosanum, a well-known Chinese herb shown to be protective against hepatic cancer as well as liver and lung damage, may be attributed to the presence of abundant carotenoids and chlorophylls. However, the variety and content of chlorophylls remain uncertain. The objectives of this study were to develop an high-performance liquid chromatography-diode array detection-mass spectrometry method for determination of chlorophylls in T. formosanum and preparation by column chromatography. An HyPURITY C18 column and a gradient mobile phase of water (A), methanol (B), acetonitrile (C), and acetone (D) could resolve 10 chlorophylls and an internal standard Fast Green FCF within 30 min with a flow rate at 1 mL/min and detection at 660 nm. Both chlorophylls a and a' were present in the largest amount (1389.6 ?g/g), followed by chlorophylls b and b' (561.2 ?g/g), pheophytins a and a' (31.7 ?g/g), hydroxychlorophyll b (26.5 ?g/g), hydroxychlorophylls a and a' (9.8 ?g/g), and chlorophyllides a and a' (0.35 ?g/g). A glass column containing 52 g of magnesium oxide-diatomaceous earth (1:3, w/w) could elute chlorophylls with 800 mL of acetone containing 50% ethanol at a flow rate of 10 mL/min. Some new chlorophyll derivatives including chlorophyllide b, pyropheophorbide b, hydroxypheophytin a, and hydroxypheophytin a' were generated during column chromatography but accompanied by a 63% loss in total chlorophylls. Thus, the possibility of chlorophyll fraction prepared from T. formosanum as a raw material for future production of functional food needs further investigation. PMID:22656126
Separation and quantification of 15 carotenoids by reversed phase high performance liquid chromatography coupled to diode array detection with isosbestic wavelength approach.
Mitrowska, Kamila; Vincent, Ursula; von Holst, Christoph
The manuscript presents the development of a new reverse phase high performance liquid chromatography (RP-HPLC) photo diode array detection method allowing the separation and quantification of 15 carotenoids (adonirubin, adonixanthin, astaxanthin, astaxanthin dimethyl disuccinate, asteroidenone, beta-apo-8'-carotenal, beta-apo-8'-carotenoic acid ethyl ester, beta-carotene, canthaxanthin, capsanthin, citranaxanthin, echinenone, lutein, lycopene, and zeaxanthin), 10 of which are feed additives authorised within the European Union. The developed method allows for the reliable determination of the total carotenoid content in one run using the corresponding E-isomer as calibration standard while taking into account the E/Z-isomers composition. This is a key criterion for the application of the method, since for most of the analytes included in this study analytical standards are only available for the E-isomers. This goal was achieved by applying the isosbestic concept, in order to identify specific wavelengths, at which the absorption coefficients are identical for all stereoisomers concerned. The second target referred to the optimisation of the LC conditions. By means of an experimental design, an optimised RP-HPLC method was developed allowing for a sufficient chromatographic separation of all carotenoids. The selected method uses a Suplex pKb-100 HPLC column and applying a gradient with a mixture of acetonitrile, tert-butyl-methyl ether and water as mobile phases. The limits of detection and limits of quantification ranged from 0.06 mg L(-1) to 0.14 mg L(-1) and from 0.20 mg L(-1) to 0.48 mg L(-1), respectively. PMID:22377469
Development and validation of an high-performance liquid chromatography-diode array detector method for the simultaneous determination of six phenolic compounds in abnormal savda munziq decoction
Tian, Shuge; Liu, Wenxian; Liu, Feng; Zhang, Xuejia; Upur, Halmuart
Aims: Given the high-effectiveness and low-toxicity of abnormal savda munziq (ASMQ), its herbal formulation has long been used in traditional Uyghur medicine to treat complex diseases, such as cancer, diabetes, and cardiovascular diseases. Settings and Design: ASMQ decoction by reversed-phase high-performance liquid chromatography coupled with a diode array detector was successfully developed for the simultaneous quality assessment of gallic acid, protocatechuic acid, caffeic acid, rutin, rosmarinic acid, and luteolin. The six phenolic compounds were separated on an Agilent TC-C18 reversed-phase analytical column (4.6 ū 250 mm, 5 ?m) by gradient elution using 0.3% aqueous formic acid (v/v) and 0.3% methanol formic acid (v/v) at 1.0 mL/min. Materials and Methods: The plant material was separately ground and mixed at the following ratios (10): Cordia dichotoma (10.6), Anchusa italic (10.6), Euphorbia humifusa (4.9), Adiantum capillus-veneris (4.9), Ziziphus jujube (4.9), Glycyrrhiza uralensis (7.1), Foeniculum vulgare (4.9), Lavandula angustifolia (4.9), Dracocephalum moldavica L. (4.9), and Alhagi pseudoalhagi (42.3). Statistical Analysis Used: The precisions of all six compounds were <0.60%, and the average recoveries ranged from 99.39% to 104.85%. Highly significant linear correlations were found between component concentrations and specific chromatographic peak areas (R2 > 0.999). Results: The proposed method was successfully applied to determine the levels of six active components in ASMQ. Conclusions: Given the simplicity, precision, specificity, and sensitivity of the method, it can be utilized as a quality control approach to simultaneously determining the six phenolic compounds in AMSQ. PMID:25709227
ERIC Educational Resources Information Center
Molde, Trevor
Outlines the discovery and nature of ultraviolet light, discusses some applications for these wavelengths, and describes a number of experiments with ultraviolet radiation suitable for secondary school science classes. (JR)
Nitride deep-ultraviolet light-emitting diodes with microlens array M. Khizar, Z. Y. Fan, K. H. Kim, J. Y. Lin, and H. X. Jianga
Jiang, Hongxing
biological and chemical agent detec- tion, high-density data storage, and air-water purification and medical of the material quality and device structure is critical for the device perfor- mance. On the other hand by resist thermal reflow and plasma dry etching. LED devices were flip-chip bonded on high thermal
Fast separation and determination of tyrosol, hydroxytyrosol and other phenolic compounds in extra-virgin olive oil by capillary zone electrophoresis with ultraviolet-diode array detection
Matteo Bonoli; Marina Montanucci; Tullia Gallina Toschi; Giovanni Lercker
Olive oil is the main source of fat in the Mediterranean diet, and its consumption has been related to a low incidence of coronary heart disease and certain cancers. Recent findings demonstrate that olive oil phenolics are powerful in vitro and in vivo antioxidants and display other biological activities that could partially account for the observed healthful effects of the
Development and validation of a rapid ultra-high performance liquid chromatography diode array detector method for Vitex agnus-castus.
H÷gner, C; Sturm, S; Seger, C; Stuppner, H
A rapid ultra-high performance liquid chromatography diode array detector (UHPLC-DAD) method was developed and validated for the simultaneous determination of all classes of non-volatile phytochemicals (iridoids, flavonoids and diterpenes) in Vitex agnus-castus (Lamiaceae) fruits, a traditional medicinal plant used against premenstrual symptoms (PMS) and other disorders. Seven marker compounds, 3,4-dihydroxybenzoic acid, p-hydroxybenzoic acid, agnuside, 5-hydroxykaempferol-3,6,7,4'-tetramethylether, 1,2-dibenzoic acid glucose, methoxy-vitexilactone, and vitetrifolin D were isolated from the methanol extract of V. agnus-castus to be used as reference substances. Chromatographic separation was performed on a Zorbax Eclipse XDB-C18 (50mmū2.1mm) UHPLC column with 1.8?m particle size, within 20min. A solvent gradient from 0.5% acetic acid to acetonitrile at a flow rate of 0.6mL/min was used as mobile phase. Analyte detection and quantification was realized at 210nm and 260nm. The UHPLC-DAD assay was validated for the quantitative analysis of agnuside, isovitexin, casticin, 5-hydroxykaempferol-3,6,7,4'-tetramethylether and vitetrifolin D. It was found to be specific, accurate, precise, and reproducible for the quantification of these compound within a concentration range of 0.7-500.0?g/mL for casticin and 5-hydroxykaempferol-3,6,7,4'-tetramethylether, 1.4-1000.0?g/mL for isovitexin and agnuside, and 12.4-1000.0?g/mL for vitetrifolin D. Intra- and inter-day variations showed relative standard deviations (RSD) of less than 3.9% and 6.4%, respectively. Tentatively assignment of 62 chromatographic features found in the UHPLC-DAD assay was carried out by coupling the UHPLC instrument to a quadrupole time-of-flight mass spectrometer via an electrospray ionization interface (ESI-QTOF-MS) operated in positive and negative ion mode. By using the established quantitative UHPLC-DAD assay to asses agnuside, isovitexin, casticin, 5-hydroxykaempferol-3,6,7,4'-tetramethylether and vitetrifolin D in V. agnus-castus derived preparations as extracts, tinctures and tablets, the applicability of the developed assay to phytopharmaceuticals was successfully proven. PMID:23522912
Extending the Astronomical Application of Photon Counting HgCdTe Linear Avalanche Photo-Diode Arrays to Low Background Space Observations.
NASA Astrophysics Data System (ADS)
Hall, Donald
The high quantum efficiency and very low dark current, together with the ability to set the wavelength cutoff from one to far beyond 5.5 microns, of large format HAWAII HgCdTe arrays have already made them the workhorse for NASA space astronomy (and related) observations in the 1 to 5.5 micron infrared. They have performed outstandingly on Hubble Wide Field Camera 3 and WISE (and also Deep Impact/EPOXI and OCO-2) and are crucial to the two major NASA Astrophysics missions, JWST and WFIRST, and to Euclid. The proposed investigation seeks to extend these benefits to the most demanding observations those that seek to wring information from only a few photons (starved due to either the intrinsic faintness of the source or the need for high spectral or time resolution) or to discriminate a weak signature against a bright source. We will characterize, and optimize for space astronomy observations, the unique linear avalanche properties of HgCdTe photo-diodes (HgCdTe L-APDs) that allow noiseless (i.e. faithfully preserves the Poisson statistics of the incoming photons) avalanche multiplication of individual photo-electrons. 2.5 micron HgCdTe L-APD technology, developed for infrared eye-safe LIDAR and range gated imaging, is already benefiting infrared wavefront sensing for ground based adaptive optics. In HgCdTe the L-APD gain and the onset voltage for tunneling current are exponential functions of bandgap while also varying with cryogenic operating temperature. The unique HgCdTe bandgap engineering that allows tuning of the cutoff wavelength can be used to critically improve avalanche performance for specific applications. We will thoroughly evaluate avalanche performance at several representative bandgaps so as to allow model prediction of performance over the critical 1 to 5 micron spectral interval. The proposed investigation will hybridize modest 32x32 arrays of HgCdTe L-APDs to photon counting readouts already developed under another award and characterize their infrared photon counting performance at the low and ultra-low backgrounds required for NASA space astronomy missions. Specifically this will involve 1) Measuring the gain normalized dark count rate and avalanche gain of 2.5, 3.3 and 4 micron cutoff HgCdTe at cryogenic temperatures from 30 to 80 K and bias voltages up to 20 V, 2) Using these results to validate and refine models of avalanche gain along with generation- recombination and surface trap induced tunneling current in L-APD HgCdTe and, 3) Modeling the gain normalized dark count rate, surface tunneling current and avalanche gain of 2 to 5 micron cutoff HgCdTe L-APD arrays for astrophysics and other NASA missions. The overall objective of the investigation is to develop the tools to identify the sweet spot in bandgap and cryogenic operating temperature for each specific NASA astrophysics mission and to accurately predict ultimate performance. HgCdTe L-APD technology offers to NASA the ultimate performance for space astronomy in photon starved applications such as: 1) ultra-low background, extra- Zodiacal imaging and faint object spectroscopy from elliptical orbits beyond the asteroid belt with missions such as Extra-Zodiacal Explorer, 2) spectroscopy of the faintest O/IR sources from near earth and L-2 orbit at moderate to high resolution and, 3) time domain astronomy observations (photometric or spectral variations at frequencies above 1 Hz) of sources as diverse as close binaries, accretion disks, compact objects etc. HgCdTe L- APD arrays have the potential to enable new classes of missions and to bring critical observations within reach of the capabilities of the NASA SMD Astrophysics Explorer program. As they utilize the same mature TRL base as the large format JWST HgCdTe arrays, requiring only qualification of n-on-p material operated at higher bias voltages, the path to flight qualification is unusually direct.
Ultraviolet Communication Network Modeling and Analysis
Wang, Leijie
and Optics - Free Space Laser Communications IX, San Diego,in free-space optical communication using laser diode [12].laser or a LED array could be employed for long distance free-space UV communication,
Integrated injection-locked semiconductor diode laser
Hadley, G. Ronald (Albuquerque, NM); Hohimer, John P. (Albuquerque, NM); Owyoung, Adelbert (Albuquerque, NM)
A continuous wave integrated injection-locked high-power diode laser array is provided with an on-chip independently-controlled master laser. The integrated injection locked high-power diode laser array is capable of continuous wave lasing in a single near-diffraction limited output beam at single-facet power levels up to 125 mW (250 mW total). Electronic steering of the array emission over an angle of 0.5 degrees is obtained by varying current to the master laser. The master laser injects a laser beam into the slave array by reflection of a rear facet.
Integrated injection-locked semiconductor diode laser
Hadley, G.R.; Hohimer, J.P.; Owyoung, A.
A continuous wave integrated injection-locked high-power diode laser array is provided with an on-chip independently-controlled master laser. The integrated injection locked high-power diode laser array is capable of continuous wave lasing in a single near-diffraction limited output beam at single-facet power levels up to 125 mW (250 mW total). Electronic steering of the array emission over an angle of 0.5 degrees is obtained by varying current to the master laser. The master laser injects a laser beam into the slave array by reflection of a rear facet. 18 figures.
SiC-Based Schottky Diode Gas Sensors
NASA Technical Reports Server (NTRS)
Hunter, Gary W.; Neudeck, Philip G.; Chen, Liang-Yu; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai
Silicon carbide based Schottky diode gas sensors are being developed for high temperature applications such as emission measurements. Two different types of gas sensitive diodes will be discussed in this paper. By varying the structure of the diode, one can affect the diode stability as well as the diode sensitivity to various gases. It is concluded that the ability of SiC to operate as a high temperature semiconductor significantly enhances the versatility of the Schottky diode gas sensing structure and will potentially allow the fabrication of a SiC-based gas sensor arrays for versatile high temperature gas sensing applications.
Characterization and quantitative analysis of phenylpropanoid amides in eggplant (Solanum melongena L.) by high performance liquid chromatography coupled with diode array detection and hybrid ion trap time-of-flight mass spectrometry.
Sun, Jing; Song, Yue-Lin; Zhang, Jing; Huang, Zheng; Huo, Hui-Xia; Zheng, Jiao; Zhang, Qian; Zhao, Yun-Fang; Li, Jun; Tu, Peng-Fei
Eggplant (Solanum melongena L.) is a famous edible and medicinal plant. Despite being widely cultivated and used, data on certain parts other than the fruit are limited. The present study focused on the qualitative and quantitative analysis of the chemical constituents, particularly phenylpropanoid amides (PAs), in eggplant. The mass fragmentation patterns of PAs were proposed using seven authentic compounds with the assistance of a hybrid ion trap time-of-flight mass spectrometer. Thirty-seven compounds (27 PAs and 10 others) were detected and plausibly assigned in the different parts of eggplant. Afterward, a reliable method based on liquid chromatography coupled with diode array detection was developed, validated, and applied for the simultaneous determination of seven PAs and three caffeoylquinic acids in 17 batches of eggplant roots with satisfactory accuracy, precision, and reproducibility, which could not only provide global chemical insight of eggplant but also offer a reliable tool for quality control. PMID:25796999
The offline combination of thin-layer chromatography and high-performance liquid chromatography with diode array detection and micrOTOF-Q mass spectrometry for the separation and identification of spinochromes from sea urchin (Strongylocentrotus droebachiensis) shells.
Shikov, Alexander N; Ossipov, Vladimir I; Martiskainen, Olli; Pozharitskaya, Olga N; Ivanova, Svetlana A; Makarov, Valery G
Thin-layer chromatography (TLC) with off-line high-performance liquid chromatography coupled to diode array detection and micrOTOF-Q mass spectrometry (HPLC-DAD-MS) resulted in the successful fractionation, separation and identification of spinochrome pigments from sea urchin (Strongylocentrotus droebachiensis) shells. Two fractions of pigments were separated by TLC and eluted with methanol using a TLC-MS interface. HPLC-DAD-MS analysis of the fractions indicated the presence of six sea urchin pigments: spinochrome monomers B and D, three spinochrome dimers (anhydroethylidene-6,6'-bis(2,3,7-trihydroxynaphthazarin) and its isomer and ethylidene-6,6'-bis(2,3,7-trihydroxynaphthazarin)), and one pigment that was preliminary identified as a spinochrome dimer with the structural formula C(22)H(16)O(16). PMID:22078305
Multimode-diode-pumped gas (alkali-vapor) laser
Ralph H. Page; Raymond J. Beach; V. Keith Kanz; William F. Krupke
We report what we believe to be the first demonstration of a multimode-diode-pumped gas laser: Rb vapor operating on the 795 nm D1 resonance transition. Peak output of ś1W was obtained using a volume-Bragg-grating stabilized pump diode array. The laser's output radiance exceeded the pump radiance by a factor greater than 2000. Power scaling (by pumping with larger diode arrays)
Multimode-diode-pumped gas (alkali-vapor) laser
R H Page; R J Beach; V K Kanz
We report the first demonstration of a multimode-diode-pumped gas laser--Rb vapor operating on the 795 nm resonance transition. Peak output of Ō1 Watt was obtained using a volume-Bragg-grating stabilized pump diode array. The laser's output radiance exceeded the pump radiance by a factor greater than 2000. Power scaling (by pumping with larger diode arrays) is therefore possible.
Robert J. Mailloux; Hanscom AFB
Throughout the years, electronic scanning of arrays has been accomplished using a variety of electromechanical and electronic components or frequency dependence to introduce phase shift or time delay at each of the antenna array radiators. Ferrite and diode phase shifters and MMIC modules are the technologies that have developed to address the control task. There is a continuing need to
Improved Waveguide Laser Array
NASA Technical Reports Server (NTRS)
Mukai, S.; Lindsey, C. P.; Katz, J.; Kapon, E.; Yariv, A.; Margalit, S.
Improved structure for integrated array of AlxGa1-xAs diode lasers causes array to oscillate predominantly in fundamental supermode (with all units at same phase), thereby producing intense, narrow light beam. New structure differs from older ones in that gain in spaces between laser channels is approximately equal to gain in channels.
The bypass diode assembly: solar cell protection for Space Station Freedom
T. W. Woike; S. C. Stotlar; L. Woods
When a shadow partially obscures a large solar array, the large power dissipated in the reverse direction can degrade the shadowed cell. A bypass diode, a diode connected in reverse polarity to the solar cell, can prevent damage to the solar cell and thus extend the operable life of the solar array. A single bypass diode for the Space Station
Diode-laser deceleration and collimation of a rubidium beam
B. Sheehy; Song-Quan Shang; R. N. Watts; S. Hatamian; Harold J. Metcalf
We report the use of frequency-chirped diode lasers to decelerate a thermal atomic beam of Rb and, in a separate experiment, the use of frequency-stabilized diode lasers to collimate the beam with optical molasses. For this we used a 100-mW cw laser-diode array injection locked to light from a low-power, frequency-narrowed, single-stripe diode laser. Also, a novel scheme for imaging
Qualitative and quantitative analysis of the major constituents in Chinese medicinal preparation Dan-Lou tablet by ultra high performance liquid chromatography/diode-array detector/quadrupole time-of-flight tandem mass spectrometry.
Dong, Juan; Zhu, Yan; Gao, Xiumei; Chang, Yanxu; Wang, Meng; Zhang, Peng
A rapid ultra high performance liquid chromatography/diode-array detector/quadrupole time-of-flight tandem mass spectrometry (UPLC-DAD-QTOF) method and a ultra high performance liquid chromatography coupled with diode-array detector (UPLC-DAD) method were developed for qualitative and quantitative analyses of the major chemical constituents in Dan-Lou tablet. Sixty-eight compounds including flavonoids, phenolic acids, tanshinones, protostane triterpenoids, lactones, and paeoniflorins were unambiguously or tentatively identified by comparing their retention times and accurate mass measurement in 40min with references or literature data. Among them, 19 compounds: gallic acid, danshensu, 5-hydroxymethyl-2-furaldehyde, 3'-hydroxy puerarin, puerarin, 3'-methoxy puerarin, mirificin, daidzin, paeoniflorin, calycosin-7-O-?-D-glucoside, naringin, genistin, rosmarinic acid, salvianolic acid B, salvianolic acid A, formononetin, calycosin, cryptotanshinone and tanshinone IIA were further quantified in 30min as marker substances. It was found that the calibration curves for all analytes showed good linearity (R(2)>0.9997) within the test ranges. The overall limits of detection (LODs) and limits of quantification (LOQs) were 0.0073-0.34?g/mL and 0.022-1.04?g/mL, respectively. The relative standard deviations (RSDs) for intra- and inter-day precisions were below 1.90% and 2.85%, respectively. The results of repeatability were less than 2.74%. The sample was stable for at least 48h. The mean recovery rates ranged from 95.5% to 105% with the relative standard deviations (RSDs) less than 2.96%. The results showed that the developed quantitative method was linear, sensitive, and precise for quality control of Dan-Lou tablet. PMID:23518306
Determination of organophosphorus pesticides in bovine tissue by an on-line coupled matrix solid-phase dispersion-solid phase extraction-high performance liquid chromatography with diode array detection method.
Gutiķrrez Valencia, Tania M; GarcĒa de Llasera, Martha P
A miniaturized method based on matrix solid-phase dispersion coupled to solid phase extraction and high performance liquid chromatography with diode array detection (MSPD-SPE-HPLC/DAD) was developed for the trace simultaneous determination of the following organophosphorus pesticides (OPPs) in bovine tissue: parathion-methyl, fenitrothion, parathion, chlorfenvinphos, diazinon, ethion, fenchlorphos, chlorpyrifos and carbophenothion. To perform the coupling between MSPD and SPE, 0.05 g of sample was dispersed with 0.2 g of C(18) silica sorbent and packed into a stainless steel cartridge containing 0.05 g of silica gel in the bottom. After a clean-up of high and medium polarity interferences with water and an acetonitrile:water mixture, the OPPs were desorbed from the MSPD cartridge with pure acetonitrile and directly transferred to a dynamic mixing chamber for dilution with water and preconcentration into an SPE 20 mm ū 2.0 mm I.D. C(18) silica column. Subsequently, the OPPs were eluted on-line with the chromatographic mobile phase to the analytical column and the diode array detector for their separation and detection, respectively. The method was validated and yielded recovery values between 91% and 101% and precision values, expressed as relative standard deviations (RSD), which were less than or equal to 12%. Linearity was good and ranged from 0.5 to 10 ?g g(-1), and the limits of detection of the OPPs were in the range of 0.04-0.25 ?g g(-1). The method was satisfactorily applied to the analysis of real samples and is recommended for food control, research efforts when sample amounts are limited, and laboratories that have ordinary chromatographic instrumentation. PMID:21872255
NSDL National Science Digital Library
Presented by the University of Cambridge's Engineering Department, this page contains an interactive semicondictor diode animation. Additionally, a quiz and short exam are attached to help users better understand the concept of this digital model.
Evaluation of column bleed by using an ultraviolet and a charged aerosol detector coupled to a high-temperature liquid chromatographic system.
Teutenberg, T; Tuerk, J; Holzhauser, M; Kiffmeyer, T K
In this study, five different HPLC columns were heated to 200 degrees C using a homemade heating system which can be operated in temperature programmed mode. The column bleed as an indicator of induced degradation of the stationary phase material was evaluated using a charged aerosol detector (CAD) and an ultraviolet diode array detector (UV-DAD) at different wavelengths. The silica based C-18 stationary phase gave the highest bleed, and the carbon clad titanium dioxide column the lowest bleed. This was independent of both the detection technique and the wavelength. PMID:16378619
Applications of Circular Array Sensors
Trawick, Charles D.
The application of the Reticon RO-64 annular photo-diode array to the task of optical tracking of special targets, direct optical focusing, and automatic printed circuit board inspection were studied. In order to facilitate ...
Schottky barrier diode and method thereof
NASA Technical Reports Server (NTRS)
Aslam, Shahid (Inventor); Franz, David (Inventor)
Pt/n.sup.-GaN Schottky barrier diodes are disclosed that are particularly suited to serve as ultra-violet sensors operating at wavelengths below 200 nm. The Pt/n.sup.-GaN Schottky barrier diodes have very large active areas, up to 1 cm.sup.2, which exhibit extremely low leakage current at low reverse biases. Very large area Pt/n.sup.-GaN Schottky diodes of sizes 0.25 cm.sup.2 and 1 cm.sup.2 have been fabricated from n.sup.-/n.sup.+ GaN epitaxial layers grown by vapor phase epitaxy on single crystal c-plane sapphire, which showed leakage currents of 14 pA and 2.7 nA, respectively for the 0.25 cm.sup.2 and 1 cm.sup.2 diodes both configured at a 0.5V reverse bias.
Dispersive liquid-liquid microextraction for the determination of vitamins D and K in foods by liquid chromatography with diode-array and atmospheric pressure chemical ionization-mass spectrometry detection.
Vi±as, Pilar; Bravo-Bravo, MarĒa; L¾pez-GarcĒa, Ignacio; Hernßndez-C¾rdoba, Manuel
A simple and rapid method was developed using reversed-phase liquid chromatography (LC) with both diode array (DAD) and atmospheric pressure chemical ionization mass spectrometric (APCI-MS) detection, for the simultaneous analysis of the vitamins ergocalciferol (D2), cholecalciferol (D3), phylloquinone (K1), menaquinone-4 (K2) and a synthetic form of vitamin K, menadione (K3). The Taguchi experimental method, an orthogonal array design (OAD), was used to optimize an efficient and clean preconcentration step based on dispersive liquid-liquid microextraction (DLLME). A factorial design was applied with six factors and three levels for each factor, namely, carbon tetrachloride volume, methanol volume, aqueous sample volume, pH of sample, sodium chloride concentration and time of the centrifugation step. The DLLME optimized procedure consisted of rapidly injecting 3 mL of acetonitrile (disperser solvent) containing 150 ĄL carbon tetrachloride (extraction solvent) into the aqueous sample, thereby forming a cloudy solution. Phase separation was performed by centrifugation, and the sedimented phase was evaporated with nitrogen, reconstituted with 50 ĄL of acetonitrile, and injected. The LC analyses were carried out using a mobile phase composed of acetonitrile, 2-propanol and water, under gradient elution. Quantification was carried out by the standard additions method. The APCI-MS spectra, in combination with UV spectra, permitted the correct identification of compounds in the food samples. The method was validated according to international guidelines and using a certified reference material. The validated method was applied for the analysis of vitamins D and K in infant foods and several green vegetables. There was little variability in the forms of vitamin K present in vegetables, with the most abundant vitamer in all the samples being phylloquinone, while menadione could not be detected. Conversely, cholecalciferol, which is present in food of animal origin, was the main form in infant foods, while ergocalciferol was not detected. PMID:24054666
Selective separation and determination of the synthetic colorants in beverages by magnetic solid-phase dispersion extraction based on a Fe3 O4 /reduced graphene oxide nanocomposite followed by high-performance liquid chromatography with diode array detection.
Wang, Xi; Chen, Ning; Han, Qing; Yang, Zaiyue; Wu, Jinhua; Xue, Cheng; Hong, Junli; Zhou, Xuemin; Jiang, Huijun
A facile adsorbent, a nanocomposite of Fe3 O4 and reduced graphene oxide, was fabricated for the selective separation and enrichment of synthetic aromatic azo colorants by magnetic solid-phase dispersion extraction. The nanocomposite was synthesized in a one-step reduction reaction and characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction and Brunauer-Emmett-Teller analysis. The colorants in beverages were quickly adsorbed onto the surface of the nanocomposite with strong ?-? interactions between colorants and reduced graphene oxide, and separated with the assistance of an external magnetic field. Moreover, the four colorants in beverages were detected at different wavelengths by high performance liquid chromatography with diode array detection. A linear dependence of peak area was obtained over 0.05-10 ?g/mL with the limits of detection of 10.02, 11.90, 10.41, 15.91 ng/mL for tartrazine, allure red, amaranth, and new coccine, respectively (signal to noise = 3). The recoveries for the spiked colorants were in the range of 88.95-95.89% with the relative standard deviation less than 2.66%. The results indicated that the nanocomposite of Fe3 O4 and reduced graphene oxide could be used as an excellent selective adsorbent for aromatic compounds and has potential applications in sample pretreatment. PMID:25864558
Identification and determination of 34 water-soluble synthetic dyes in foodstuff by high performance liquid chromatography-diode array detection-ion trap time-of-flight tandem mass spectrometry.
Li, Xiu Qin; Zhang, Qing He; Ma, Kang; Li, Hong Mei; Guo, Zhen
An accurate method combining high performance liquid chromatography (HPLC) with diode array detection (DAD) and ion-trap time-of-flight mass spectrometry (IT-TOF/MS) was developed for simultaneous identification and quantification of 34 water-soluble synthetic dyes in foodstuff. Fragmentation patterns of synthetic dyes were proposed based on IT-TOF/MS. The molecular ion [M+H](+) was not observed in the conventional single-stage mass spectra for most of synthetic dyes. The single-stage mass spectra of synthetic dyes all afforded the diagnostic ions [(M-nNa+nH)+H](+) or [(M-nNa+nH)-H](-) in the positive or negative mode. Doubly charged ions were the characteristic ions of azo dyes. An HPLC-DAD method was developed to analyze 34 synthetic dyes in foodstuffs. The limits of detection (LOD) for the dyes were 0.01-0.05 ?g/mL. The recoveries were between 76.1% and 105.0% with a RSD ranging from 1.4% to 6.4%. This method was successfully applied to analyzing the 34 water-soluble synthetic dyes in 21 commercial foods. PMID:25842343
Characterization of weld (Reseda luteola L.) and spurge flax (Daphne gnidium L.) by high-performance liquid chromatography-diode array detection-mass spectrometry in Arraiolos historical textiles.
Marques, Rita; Sousa, Micaela M; Oliveira, Maria C; Melo, Maria J
The natural dyes, and dye sources, in two seventeenth century Arraiolos carpets from the National Museum of Machado de Castro were analysed by high-performance liquid chromatography with UV-vis diode array detection (HPLC-DAD) and HPLC-mass spectrometry (LC-MS). Weld (Reseda luteola L.), indigo and spurge flax (Daphne gnidium L.) were found to be the dye sources, in agreement with original dyeing recipes collected during the nineteenth century. In order to fully characterize the plant sources, LC-MS conditions were optimized with plant extracts and the chromatographic separation and mass detection were enhanced. Extraction of the dyes, in the Arraiolos carpet samples, was performed using mild conditions that avoid glycoside decomposition. For the blues a dimethylformamide solution proved to be efficient for indigotin recovery. For all the other colours, an improved mild extraction method (with oxalic acid, methanol, acetone and water) was used, enabling to obtain the full dye source fingerprint, namely the flavonoid glycosides in the yellow dyes. PMID:19168183
Characterization of physalins and fingerprint analysis for the quality evaluation of Physalis alkekengi L. var. franchetii by ultra-performance liquid chromatography combined with diode array detection and electrospray ionization tandem mass spectrometry.
Zheng, Yunliang; Luan, Lianjun; Chen, Yong; Ren, Yiping; Wu, Yongjiang
Physalins are important bioactive compounds from genus Physalis. They often occur as isomers, which makes the structural elucidation difficult. In the present study, the fragmentation behavior and UV characteristics of seven physalins from genus Physalis were firstly investigated using electrospray ionization tandem mass spectrometry (ESI-MS/MS) and diode array detection (DAD). Combined with ultra-performance liquid chromatography (UPLC) and DAD, the established approach to the structural identification of physalins by ESI-MS/MS was then applied to the analysis of Physalis alkekengi L. According to the UPLC retention behavior, the diagnostic UV spectra and the molecular structural information provided by MS/MS spectra, about 19 fingerprint peaks were identified, including 14 physalins and 5 other compounds. Finally, the established fingerprint method was applied to the analysis of 31 P. alkekengi L. samples collected from different locations, which reflected their similar chemical constituent properties. The proposed method provides a scientific and technical platform to the herbal industry for quality control and safety assurance of herbal preparations that contain this class of physalins. PMID:22964457
Determination of flibanserin and tadalafil in supplements for women sexual desire enhancement using high-performance liquid chromatography with tandem mass spectrometer, diode array detector and charged aerosol detector.
Poplawska, Magdalena; Blazewicz, Agata; Zolek, Paulina; Fijalek, Zbigniew
The new compound - flibanserin - begun to appear as a synthetic adulterant in counterfeit herbal supplements used to stimulate women sexual drive. It was detected in two samples submitted to the Polish National Medicines Institute for analysis. The second sample contained also tadalafil. This study presents the LC method development which enables the determination of flibanserin and tadalafil. It employs three different detectors charged aerosol detector (CAD), diode array detector (DAD) and mass spectrometer (MS). The conditions of the elaborated method were optimized to obtain the highest sensitivity and the best resolution, especially the separation of icariin - the natural compound observed often in supplements for sexual disorders. The validation of the method proved good linearity, good accuracy and precision of the measurements recorded by all three detectors. Additionally, for CAD data, an alternative calculation method using a unified calibration function was presented and evaluated. It seems that this is the way to overcome the problem of non-availability of the reference standard of a target compound. Flibanserin content was quantified using the data of other reference standard (tadalafil). The inaccuracy of proposed indirect determination was found to be ▒3%. A statistical evaluation proved that the results obtained with all detection modes and the results calculated using a unified calibration were not significantly different (p>0.05). PMID:24531007
Simultaneous determination of carotenoids, tocopherols, and gamma-oryzanol in crude rice bran oil by liquid chromatography coupled to diode array and mass spectrometric detection employing silica C30 stationary phases.
St÷ggl, Wolfgang; Huck, Christain; Wongyai, Surapote; Scherz, Heimo; Bonn, G³nther
Crude rice bran oil contains tocopherols (vitamin E), carotenoids (vitamin A), and phytosterols, which possess antioxidant activities and show promising effects as preventive and therapeutic agents. The aim of this work was to establish methods and to compare C18 and C30 silica stationary phases in order to separate and detect tocopherols, carotenoids, and gamma-oryzanol in one single run. Comparing RP-LC on silica C18 and C30, higher resolution between all target compounds was obtained using the C30 stationary phase. Methanol was used as eluent and the elution strength was increased by the addition of tert-butyl methyl ether for highly hydrophobic analytes such as gamma-oryzanol. Detection was accomplished by diode array detection from 200 to 500 nm. Absorbance maxima were found at 295 nm for tocopherols, 324 nm for gammaoryzanol, and 450 nm for carotenoids. Furthermore, compounds were characterized and identified on the basis of their UV-spectra. Both RP systems were coupled to MS (LC-MS) by using an atmospheric pressure chemical ionization interface. PMID:16224965
Rapid and sensitive screening and characterization of phenolic acids, phthalides, saponins and isoflavonoids in Danggui Buxue Tang by rapid resolution liquid chromatography/diode-array detection coupled with time-of-flight mass spectrometry.
Qi, Lian-Wen; Wen, Xiao-Dong; Cao, Jun; Li, Chang-Yin; Li, Ping; Yi, Ling; Wang, Yu-Xia; Cheng, Xiao-Lan; Ge, Xiao-Xiao
A novel rapid resolution liquid chromatography (RRLC) method coupled with diode-array detection (DAD) and time-of-flight mass spectrometry (TOFMS) in both positive and negative modes has been developed for quick and sensitive identification of the major compounds in Danggui Buxue Tang (DBT) preparation. Significant advantages of the use of RRLC with 1.8-microm porous particles include the much higher speed of chromatographic separation and great enhancement in sensitivity, compared with the conventional high-performance liquid chromatography (HPLC). With dynamic adjustment of the key role as fragmentor voltage in TOFMS, an efficient transmission of the ions was achieved to obtain the best sensitivity for providing the molecular formula for each analyte, and abundant fragment ions for structural information. The structural characterization of the major compounds in DBT was elucidated with authentic standards by DAD-TOF/MS, including phenolic acids, phthalides, saponins and isoflavonoids. The targets were rapidly screened from the complicated DBT matrix using a narrow mass window of 0.01 Da to restructure extracted ion chromatograms. By accurate mass measurements within 3 ppm error for each molecular ion and subsequent fragment ions, ten phenolic acids and phthalides including three groups of isomers, thirteen major saponins with a 20,24-epoxy-9,19-cyclolanostane-3,6,16,25-tetrol skeleton, sixteen isoflavonoids, corresponding glycosides, malonylglycosides, and acetylglycosides were identified in DBT preparation. The appropriate fragmentation pathways for them were also proposed based on definite elemental composition of the fragment ions. PMID:18651584
Simultaneous Extraction Optimization and Analysis of Flavonoids from the Flowers of Tabernaemontana heyneana by High Performance Liquid Chromatography Coupled to Diode Array Detector and Electron Spray Ionization/Mass Spectrometry.
Sathishkumar, Thiyagarajan; Baskar, Ramakrishnan; Aravind, Mohan; Tilak, Suryanarayanan; Deepthi, Sri; Bharathikumar, Vellalore Maruthachalam
Flavonoids are exploited as antioxidants, antimicrobial, antithrombogenic, antiviral, and antihypercholesterolemic agents. Normally, conventional extraction techniques like soxhlet or shake flask methods provide low yield of flavonoids with structural loss, and thereby, these techniques may be considered as inefficient. In this regard, an attempt was made to optimize the flavonoid extraction using orthogonal design of experiment and subsequent structural elucidation by high-performance liquid chromatography-diode array detector-electron spray ionization/mass spectrometry (HPLC-DAD-ESI/MS) techniques. The shake flask method of flavonoid extraction was observed to provide a yield of 1.2 ▒ 0.13?(mg/g tissue). With the two different solvents, namely, ethanol and ethyl acetate, tried for the extraction optimization of flavonoid, ethanol (80.1?mg/g tissue) has been proved better than ethyl acetate (20.5?mg/g tissue). The optimal conditions of the extraction of flavonoid were found to be 85░C, 3 hours with a material ratio of 1?:?20, 75% ethanol, and 1 cycle of extraction. About seven different phenolics like robinin, quercetin, rutin, sinapoyl-hexoside, dicaffeic acid, and two unknown compounds were identified for the first time in the flowers of T. heyneana. The study has also concluded that L16 orthogonal design of experiment is an effective method for the extraction of flavonoid than the shake flask method. PMID:25969771
Quantitative analysis of triazine herbicides in environmental samples by using high performance liquid chromatography and diode array detection combined with second-order calibration based on an alternating penalty trilinear decomposition algorithm.
Li, Yuan-Na; Wu, Hai-Long; Qing, Xiang-Dong; Li, Quan; Li, Shu-Fang; Fu, Hai-Yan; Yu, Yong-Jie; Yu, Ru-Qin
A novel application of second-order calibration method based on an alternating penalty trilinear decomposition (APTLD) algorithm is presented to treat the data from high performance liquid chromatography-diode array detection (HPLC-DAD). The method makes it possible to accurately and reliably analyze atrazine (ATR), ametryn (AME) and prometryne (PRO) contents in soil, river sediment and wastewater samples. Satisfactory results are obtained although the elution and spectral profiles of the analytes are heavily overlapped with the background in environmental samples. The obtained average recoveries for ATR, AME and PRO are 99.7▒1.5, 98.4▒4.7 and 97.0▒4.4% in soil samples, 100.1▒3.2, 100.7▒3.4 and 96.4▒3.8% in river sediment samples, and 100.1▒3.5, 101.8▒4.2 and 101.4▒3.6% in wastewater samples, respectively. Furthermore, the accuracy and precision of the proposed method are evaluated with the elliptical joint confidence region (EJCR) test. It lights a new avenue to determine quantitatively herbicides in environmental samples with a simple pretreatment procedure and provides the scientific basis for an improved environment management through a better understanding of the wastewater-soil-river sediment system as a whole. PMID:20869500
High-performance liquid chromatography-diode array detection-electrospray ionization multi-stage mass spectrometric screening of an insect/plant system: the case of Spodoptera littoralis/Lycopersicon esculentum phenolics and alkaloids.
Ferreres, Federico; Taveira, Marcos; Gil-Izquierdo, Angel; Oliveira, LuĒsa; Teixeira, TŌnia; ValentŃo, PatrĒcia; Sim§es, Nelson; Andrade, Paula B
High-performance liquid chromatography-diode array detection-electrospray ionization multi-stage mass spectrometry (HPLC-DAD-ESI-MS(n)) is considered to be a very valuable tool for the characterization of compounds found in trace amounts in natural matrices, as their previous isolation and clean-up steps can be avoided. Micro-scale separation increases the potential of this analytical technique, allowing the determination of compounds in reduced samples. Spodoptera littoralis represents a major challenge to Solanaceae plants, as it is one of the most deleterious pests. The S. littoralis/Lycopersicon esculentum system was studied for the first time concerning glycoalkaloids and phenolics. Using HPLC-DAD-ESI-MS(n) we were able to characterize 15 phenolic compounds in L. esculentum leaves. Nine of them are reported for the first time. Some differences were found between leaves of cerasiforme and 'Bull's heart' varieties. However, in the materials of S. littoralis (larvae, adults, exuviae and excrements) reared in both L. esculentum leaves no phenolics were identified. ?-Tomatine was the main glycoalkaloid in the host plant. The glycoalkaloid composition of the different S. littoralis materials was distinct, with ?-tomatine and dehydrotomatine being the main detected compounds in larvae and excrements. These results add knowledge to the ecological interaction in this insect/plant duo, for which it is hard to obtain considerable sample amounts. PMID:21698680
Computer-aided method for identification of major flavone/flavonol glycosides by high-performance liquid chromatography-diode array detection-tandem mass spectrometry (HPLC-DAD-MS/MS).
Wang, Zhengfang; Lin, Longze; Harnly, James M; Harrington, Peter de B; Chen, Pei
A new computational tool is proposed here for tentatively identifying major (UV quantifiable) flavone/flavonol glycoside peaks of high performance liquid chromatogram (HPLC)-diode array detection (DAD)-tandem mass spectrometry (MS/MS) profiles based on a MATLAB-based script implementing an in-house algorithm. The HPLC-DAD-MS/MS profiles of red onion, Chinese lettuce, carrot leaf, and celery seed extracts were analyzed by the proposed computer-aided screening method for identifying possible flavone/flavonol glycoside peaks from the HPLC-UV and MS total ion current (TIC) chromatograms. The number of identified flavone/flavonol glycoside peaks of the HPLC-UV chromatograms is four, four, six, and nine for red onion, Chinese lettuce, carrot leaf, and celery seed, respectively. These results have been validated by human(s) experts. For the batch processing of nine HPLC-DAD-MS/MS profiles of celery seed extract, the entire script execution time was within 15 s while manual calculation of only one HPLC-DAD-MS/MS profile by a flavonoid expert could take hours. Therefore, this MATLAB-based screening method is able to facilitate the HPLC-DAD-MS/MS analysis of flavone/flavonol glycosides in plants to a large extent. PMID:25270867
Location of the hydroxyl functions in hydroxylated metabolites of nebivolol in different animal species and human subjects as determined by on-line high-performance liquid chromatography-diode-array detection.
Hendrickx, J; Bockx, M; Zwijsen, C; Borgmans, C; Mannens, G; Meuldermans, W; Heykants, J
Nebivolol hydrochloride (R067555), is a new antihypertensive drug. Aromatic and alicyclic hydroxylation at the benzopyran ring systems of nebivolol are important metabolic pathways. Generally, NMR is used to unambiguously assign the sites of hydroxylation. Because of the low dose rates and the extensive metabolism of nebivolol in the different species, NMR identification is not always possible, and therefore another spectroscopic technique was searched for to address this problem. UV-chromophore absorption is affected by the kind and arrangement of adjacent atoms and groups (auxochromes). The effect of these auxochromes (e.g. -NH2, -NR2, -SH, -OH, -OR and halogens) can be strongly influenced by the pH. This paper proves that HPLC at high pH combined with on-line diode-array detection is an excellent technique for the location of the hydroxyl functions in hydroxylated metabolites of nebivolol. With this technique it is possible to differentiate between glucuronidation at the automatic and aliphatic or alicyclic hydroxyl functions. PMID:9004959
Multi-responses extraction optimization combined with high-performance liquid chromatography-diode array detection-electrospray ionization-tandem mass spectrometry and chemometrics techniques for the fingerprint analysis of Aloe barbadensis Miller.
Zhong, Jia-Sheng; Wan, Jin-Zhi; Ding, Wen-Jing; Wu, Xiao-Fang; Xie, Zhi-Yong
A quality control strategy using high-performance liquid chromatography-diode array detector-electrospray ionization-tandem mass spectrometry (HPLC-DAD-ESI-MS/MS) coupled with chemometrics analysis was proposed for Aloe barbadensis Miller. Firstly, the extraction conditions including methanol concentration, extraction time and solvent-to-material ratio were optimized by multi-responses optimization based on response surface methodology (RSM). The optimum conditions were achieved by Derringer's desirability function and experimental validation implied that the established model exhibited favorable prediction ability. Then, HPLC fingerprint consisting of 27 common peaks was developed among 15 batches of A. barbadensis samples. 25 common peaks were identified using HPLC-DAD-ESI-MS/MS method by their spectral characteristics or comparison with the authentic standards. Chemometrics techniques including similarity analysis (SA), principal components analysis (PCA) and hierarchical clustering analysis (HCA) were implemented to classify A. barbadensis samples. The results demonstrated that all A. barbadensis samples shared similar chromatographic patterns as well as differences. These achievements provided an effective, reliable and comprehensive quality control method for A. barbadensis. PMID:25590942
Rapid Identification and Simultaneous Quantification of Multiple Constituents in Nao-Shuan-Tong Capsule by Ultra-Fast Liquid Chromatography/Diode-Array Detector/Quadrupole Time-of-Flight Tandem Mass Spectrometry.
Li, Panlin; Su, Weiwei; Xie, Chengshi; Zeng, Xuan; Peng, Wei; Liu, Menghua
A rapid and high-sensitive ultra-fast liquid chromatography coupled with a diode-array detector and a quadrupole/time-of-flight mass spectrometry (MS) method was established and validated for the chemical profiling of Nao-shuan-tong capsule (NSTC) and simultaneous quantification of five major constituents. A total of 59 components including monoterpene glycosides, flavonoids, sesquiterpenoids, ketosteroids, thiophenes, organic acids and alkaloids were identified or tentatively characterized in NSTC based on the accurate mass and tandem MS behavior. Five major bioactive constituents were chosen as the chemical indexes of holistic quality evaluation and quantified simultaneously. All calibration curves showed good linear regression (r(2) > 0.9991) in the range 25.2-510, 145-2,900, 1.84-36.8, 2.61-52.2 and 3.25-26.2 ?g/mL for gastrodin, paeoniflorin, typhaneoside, ?-ecdysterone and isorhamnetin-3-O-neohesperidoside, respectively. It also showed good precision, stability and accuracy for quantification of these five compounds. The limit of detections and limit of quantitations for the analytes ranged from 0.14 to 1.09 ?g/mL and from 0.47 to 3.63 ?g/mL, respectively. The validated quantification method was applied to analyze 10 batches of commercial NSTC. These results will provide a basis for quality control of the production process and the further pharmacological study in vivo of NSTC. PMID:25355899
Methods of analysis by the U.S. Geological Survey Organic Geochemistry Research Group; determination of chloroacetanilide herbicide metabolites in water using high-performance liquid chromatography-diode array detection and high-performance liquid chromatography/mass spectrometry
Zimmerman, L.R.; Hostetler, K.A.; Thurman, E.M.
Analytical methods using high-performance liquid chromatography-diode array detection (HPLC-DAD) and high-performance liquid chromatography/mass spectrometry (HPLC/MS) were developed for the analysis of the following chloroacetanilide herbicide metabolites in water: acetochlor ethanesulfonic acid (ESA), acetochlor oxanilic acid (OXA), alachlor ESA, alachlor OXA, metolachlor ESA, and metolachlor OXA. Good precision and accuracy were demonstrated for both the HPLC-DAD and HPLC/MS methods in reagent water, surface water, and ground water. The mean HPLC-DAD recoveries of the chloroacetanilide herbicide metabolites from water samples spiked at 0.25, 0.50, and 2.0 mg/L (micrograms per liter) ranged from 84 to 112 percent, with relative standard deviations of 18 percent or less. The mean HPLC/MS recoveries of the metabolites from water samples spiked at 0.05, 0.20, and 2.0 mg/L ranged from 81 to 125 percent, with relative standard deviations of 20 percent or less. The limit of quantitation (LOQ) for all metabolites using the HPLC-DAD method was 0.20 mg/L, whereas the LOQ using the HPLC/MS method was 0.05 mg/L. These metabolite-determination methods are valuable for acquiring information about water quality and the fate and transport of the parent chloroacetanilide herbicides in water.
Method validation and simultaneous determination of retinol, retinyl palmitate, ?-carotene, ?-tocopherol and vitamin C in rat serum treated with 7,12 dimethylbenz[a]anthracene and Plantago major L. by high- performance liquid chromatography using diode-array detection.
Levent, Abdulkadi; Oto, Gokhan; Ekin, Suat; Berber, Ismet
A new and simple high-performance liquid chromatography method was developed and validated for the simultaneous determination of retinol, retinyl palmitate, ?-carotene, ?-tocopherol and vitamin C in rat serum treated with Plantago Major L. and 7,12 dimethylbenz[a]anthracene. High-performance liquid chromatography analysis was performed utilizing an Inertsil ODS3 reversed phase column with methanol-tetrahydrofuran-water as mobile phase under gradient conditions, at 1.5 mL min(-1) flow rate and 25 ░C. Diode-array detection was at 325, 450, 290 and 270 nm (retinol and retinyl palmitate), ?-carotene, ?-tocopherol and vitamin C, respectively and runnig time 18 min. The high-performance liquid chromatography assay and extraction procedure proposed are simple, rapid, sensitive and accurate. The method was then applied for the determination of retinol, retinyl palmitate, ?-carotene, ?-tocopherol and vitamin C in rat serum. Results of this study demonstrated that; at 60th day DMBA-treated group, there was a significant decrease in vitamin levels compared to the levels of control group. A significant increase was observed in vitamin levels of 7,12 dimethylbenz[?]anthracene+Plantago Major L.-treated group compared to the DMBA-treated group. Additionally, the results obtained in the study are found to be in agreement with data reported in the literature. PMID:23176060
Solid-phase extraction combined with headspace single-drop microextraction of chlorophenols as their methyl ethers and analysis by high-performance liquid chromatography-diode array detection.
Sharma, Nisha; Jain, Archana; Singh, Vandana Kumari; Verma, Krishna K
Solid-phase extraction (SPE) of phenol and chlorophenols, their derivatization to methyl ethers, headspace single-drop microextraction (HS-SDME) of methyl ethers using 1-butanol as extraction solvent, and direct transfer of the drop into the injector for high performance liquid chromatography with diode array detection (HPLC-DAD) have been reported. A flanged-end polytetrafluoroethylene sleeve, 3 mm ū 0.5mm, placed at the tip of the syringe needle, allowed the use of 10 ?L solvent drop for extraction. The procedure has been optimized for variables involved in SPE and HS-SDME. A rectilinear relationship was obtained between the amount of chlorophenols and peak area ratio of their methyl ethers/internal standard (4-methoxyacetophenone) in the range 0.01-10 mg L(-1), correlation coefficient in the range 0.9956-0.9996, and limit of detection in the range 1.5-3.9 ?g L(-1) when HS-SDME alone was used for sample preparation. When using coupled SPE and HS-SDME, the linear range obtained was 0.1-500 ?g L(-1), correlation coefficient in the range 0.9974-0.9998, and the limit of detection in the range 0.04-0.08 ?g L(-1). Spiked real samples have been analyzed with adequate accuracy, and application of the method has been demonstrated for the analysis of chlorophenols formed upon bamboo pulp bleaching. PMID:21147349
Analysis and improved characterization of minor antioxidants from leaves of Malus doumeri using a combination of major constituents' knockout with high-performance liquid chromatography-diode array detector-quadrupole time-of-flight tandem mass spectrometry.
Zhao, Huading; Hu, Xin; Chen, Xiaoqin; Shi, Shuyun; Jiang, Xinyu; Liang, Xuejuan; Chen, Wei; Zhang, Shuihan
Due to the complexity of natural products, efficient identification of bioactive compounds, especially for minor compounds, would require a huge effort. Here, we developed an effective strategy based on combining major constituents' knockout with high-performance liquid chromatography-diode array detector-quadrupole time-of-flight tandem mass spectrometry (HPLC-DAD-QTOF-MS/MS) to comprehensively identify minor antioxidants in Malus doumeri, one of the longest known and most used tonic plant in Taiwan. First, five major compounds (I-V) in M. doumeri were knocked out by two-step stepwise high-speed countercurrent chromatography (HSCCC). Second, minor antioxidants were screened by 1,1-diphenyl-2-picrylhydrazyl radical-HPLC (DPPH-HPLC) assay. Third, structures of thirty minor antioxidants, including 11 dihydrochalcones, 4 flavanones, 3 flavonols, 2 flavones, 3 aurones and 7 phenolic acids, were unambiguously or tentatively identified by matching their characteristic UV spectra, accurate mass signals and key diagnostic fragment ions with standards or previously reported compounds. Twenty-six of them, as far as was known, were discovered from M. doumeri for the first time. The results indicated that the proposed method was a useful approach to explore minor bioactive compounds from complex natural products. PMID:25912788
Characterization of flavonoid metabolites in rat plasma, urine, and feces after oral administration of Semen Ziziphi Spinosae extract by HPLC-diode-array detection (DAD) and ion-trap mass spectrometry (MS(n)).
Bao, Kang-De; Li, Ping; Qi, Lian-Wen; Li, Hui-Jun; Yi, Ling; Wang, Wei; Wang, Ya-Qiong
A highly specific and sensitive method using high performance liquid chromatography coupled with diode-array detection and ion-trap mass spectrometry (HPLC-DAD-MS(n)) was developed for study of the constituents of flavonoid extract of jujube seeds and the metabolites in rat plasma, urine, and feces samples after oral administration of flavonoid extract of jujube seeds. Two major flavonoids (spinosin and 6'''-feruloylspinosin) with content >60% in the flavonoid extract of jujube seeds were detected and confirmed by comparison with the reference standards. Furthermore, five metabolic components in plasma, seven in urine, and four in feces were detected and elucidated. The scientific and plausible biotransformation pathways of the main components in flavonoid extract of jujube seeds were also proposed, together with presentation of clues for potential bioactive mechanisms. This convenient HPLC-DAD-MS(n) method could be used to identify the chemical components of flavonoid extract of jujube seeds as well as their metabolites, and to reveal their possible metabolic mechanism of action in vivo. PMID:19182403
Strong photonic crystal behavior in regular arrays of core-shell and quantum disc InGaN/GaN nanorod light-emitting diodes
Lewins, C. J., E-mail: firstname.lastname@example.com; Le Boulbar, E. D.; Lis, S. M.; Shields, P. A.; Allsopp, D. W. E., E-mail: firstname.lastname@example.com [Department of Electronic and Electrical Engineering, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Edwards, P. R.; Martin, R. W. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom)
We show that arrays of emissive nanorod structures can exhibit strong photonic crystal behavior, via observations of the far-field luminescence from core-shell and quantum disc InGaN/GaN nanorods. The conditions needed for the formation of directional Bloch modes characteristic of strong photonic behavior are found to depend critically upon the vertical shape of the nanorod sidewalls. Index guiding by a region of lower volume-averaged refractive index near the base of the nanorods creates a quasi-suspended photonic crystal slab at the top of the nanorods which supports Bloch modes. Only diffractive behavior could be observed without this region. Slab waveguide modelling of the vertical structure shows that the behavioral regime of the emissive nanorod arrays depends strongly upon the optical coupling between the nanorod region and the planar layers below. The controlled crossover between the two regimes of photonic crystal operation enables the design of photonic nanorod structures formed on planar substrates that exploit either behavior depending on device requirements.
High sensitivity and fast response and recovery times in a ZnO nanorod array/p-Si self-powered ultraviolet detector
NASA Astrophysics Data System (ADS)
Hassan, J. J.; Mahdi, M. A.; Kasim, S. J.; Ahmed, Naser M.; Abu Hassan, H.; Hassan, Z.
High quality, vertically aligned ZnO nanorods were grown on a silicon substrate, using microwave-assisted chemical bath deposition with poly (vinyl alcohol)-Zn(OH)2 nanocomposites as seed layer. The structure and surface morphology of the prepared ZnO nanorod arrays were characterized using X-ray diffraction and scanning electron microscopy. The optical properties were assessed using photoluminescence measurements; the results showed a high-intensity UV peak, and a lower intensity, broader visible peak. Upon exposure to 395 nm light at a zero-bias voltage, the UV detector showed a high sensitivity of 8000% and fast response and recovery times of 25 and 22 ms, respectively.
NSDL National Science Digital Library
Zollman, Dean
This resource, part of the Spectroscopy Lab Suite, illustrates the physics of a semiconductor Diode Laser. Students can create conduction and valence band energy levels and build in a bias due to impurity doping. The basic processes for light emission, including external voltage bias and level transitions are shown. The band energy levels and internal and external bias can all be adjusted to achieve an output spectrum similar to the measured physical spectrum.
Cylindrical microlenses for collimating high-power diode lasers
Volker Sturm; Hans-Georg Treusch; Peter Loosen
Monolithic linear arrays of diode lasers, also known as diode laser bars, are the basic elements for most high-power laser applications such as solid-state laser pumping or material processing. Cylindrical microlenses used as fast- axis collimators for 10-mm diode bars require very high angles of aperture (up to 100 degree FW1\\/e2, equivalent to a numerical aperture of approx. 0.8) to
[Studies on identification of drugs of abuse by diode array detection. I. Screening-test and identification of benzodiazepines by HPLC-DAD with ICOS software system].
Shimamine, M; Masunari, T; Nakahara, Y
For the establishment of screening-test and identification of 20 benzodiazepines (Alprazolam, Bromazepam, Chlordiazepoxide, Clonazepam, Clotiazepam, Cloxazolam, Diazepam, Estazolam, Fludiazepam, Flunitrazepam, Flurazepam, Lorazepam, Lormetazepam, Medazolam, Midazepam, Nimetazepam, Nitrazepam, Oxazepam, Prazepam, Triazolam), the optimum separation condition on HPLC was investigated by using Interactive Computer Optimization for HPLC Separation (ICOS) software. The two eluent systems of 0.02M KH2PO4 (pH 3.1)-methanol-acetonitrile (66.4:5.7:27.9) and 0.1% TFA-methanol-acetonitrile (61.6:16.1:22.3) were selected by HPLC analyses using ICOS. These optimum separation conditions enabled the screening test and identification of the 20 benzodiazepines on HPLC with photodiode array detection. PMID:7920567
EE 321 Diodes 3 Fall 2008 Diodes, Part 3 --Diode and Zener Diode Circuits
Wedeward, Kevin
EE 321 Diodes 3 Fall 2008 EE321 Lab Diodes, Part 3 -- Diode and Zener Diode Circuits The purpose of this lab is build and test some interesting non-linear circuits that utilize diodes. Most of them from turning the diode on in the forward direction.) 7 6 4 +15V vouA741 3 2 470 10K Pot R 1N5229 Figure
Determination of polymer additives-antioxidants and ultraviolet (UV) absorbers by high-performance liquid chromatography coupled with UV photodiode array detection in food simulants.
Gao, Yali; Gu, Yanxiang; Wei, Yun
An analytical method for the quantitative determination of migration levels of polymer additives such as antioxidants and UV absorbers in food packages by high-performance liquid chromatography coupled with UV-vis photodiode array detection has been developed. The pretreatment step involved solid-phase extraction with silica C18 cartridges. The analytical method showed good linearity, presenting regression coefficients (R(2)) ? 0.9990 for all compounds. This optimized method was also validated with respect to precision, reproducibility, stability, and accuracy. The limits of detection and quantification were between 0.09 and 1.72 ?g mL(-1) and between 0.20 and 5.64 ?g mL(-1) for 12 analytes, respectively. Recoveries were in the range of 67.48 and 108.55%, with relative standard deviations between 2.76 and 9.81%. Migration levels of antioxidants and UV absorbers were determined. Butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol (BHT), 2,4-di-tert-butylphenol, Cyanox 2246, Irganox 1035, Tinuvin 326, Tinuvin 328, Irganox 1010, and Irganox 1330 were detected; BHT and Cyanox 2246 were at higher levels than the specific migration levels in some food simulants. PMID:22141443
An enhanced multiwavelength ultraviolet biological trigger lidar
Alexander Achey; Jack Bufton; Jeffrey Dawson; Wen Huang; Sangmin Lee; Nikhil Mehta; Coorg R. Prasad
A compact Ultraviolet Biological Trigger Lidar (UBTL) instrument for detection and discrimination of bio-warfare-agent (BWA) simulant aerosol clouds was developed by us [Prasad, et al, 2004] using a 5mW, 375nm semiconductor UV optical source (SUVOS) laser diode. It underwent successful field tests at Dugway Proving Ground and demonstrated measurement ranges of over 300m for elastic scattering and >100m for fluorescence.
Large-Area Vacuum Ultraviolet Sensors
NASA Technical Reports Server (NTRS)
Aslam, Shahid; Franz, David
Pt/(n-doped GaN) Schottky-barrier diodes having active areas as large as 1 cm square have been designed and fabricated as prototypes of photodetectors for the vacuum ultraviolet portion (wavelengths approximately equal 200 nm) of the solar spectrum. In addition to having adequate sensitivity to photons in this wavelength range, these photodetectors are required to be insensitive to visible and infrared components of sunlight and to have relatively low levels of dark current.
September 15, 2003 / Vol. 28, No. 18 / OPTICS LETTERS 1707 Application of light-emitting diodes
Davitt, Kristina
September 15, 2003 / Vol. 28, No. 18 / OPTICS LETTERS 1707 Application of light-emitting diodes compact linear array of sequentially fired light from blue light-emitting diodes. The results suggest of efficient UV light-emitting diodes. ® 2003 Optical Society of America OCIS codes: 170.6280, 010.1100, 220
Spin-exchange optical pumping using a frequency-narrowed high power diode laser
Walker, Thad G.
Spin-exchange optical pumping using a frequency-narrowed high power diode laser I. A. Nelson, B for frequency narrowing commercial high power diode lasers from 2 to 0.1 nm bandwidth with modest loss of power diode arrays for the optical pumping. The poor match between the laser bandwidth 2Ł3 nm
Low-Temperature Preparation of Ag-Doped ZnO Nanowire Arrays, DFT Study, and Application to Light-Emitting Diode.
Pauportķ, Thierry; Lupan, Oleg; Zhang, Jie; Tugsuz, Tugba; Ciofini, Ilaria; Labat, Frķdķric; Viana, Bruno
Doping ZnO nanowires (NWs) by group IB elements is an important challenge for integrating nanostructures into functional devices with better and tuned performances. The growth of Ag-doped ZnO NWs by electrodeposition at 90 ░C using a chloride bath and molecular oxygen precursor is reported. Ag acts as an electrocatalyst for the deposition and influences the nucleation and growth of the structures. The silver atomic concentration in the wires is controlled by the additive concentration in the deposition bath and a content up to 3.7 atomic % is reported. XRD analysis shows that the integration of silver enlarges the lattice parameters of ZnO. The optical measurements also show that the direct optical bandgap of ZnO is reduced by silver doping. The bandgap shift and lattice expansion are explained by first principle calculations using the density functional theory (DFT) on the silver impurity integration as an interstitial (Agi) and as a substitute of zinc atom (AgZn) in the crystal lattice. They notably indicate that AgZn doping forms an impurity band because of Ag 4d and O 2p orbital interactions, shifting the Fermi level toward the valence band. At least, Ag-doped ZnO vertically aligned nanowire arrays have been epitaxially grown on GaN(001) substrate. The heterostructure has been inserted in a light emitting device. UV-blue light emission has been achieved with a low emission threshold of 5 V and a tunable red-shifted emission spectrum related to the bandgap reduction induced by silver doping of the ZnO emitter material. PMID:25990263
A Comparison of Optical Detectors for the Visible and Ultraviolet.
ERIC Educational Resources Information Center
Grossman, William E. L.
Presents data for instructors on the current state of ultraviolet-visible detector technology and gives sources of further information. Described are the mechanisms and characteristics of photomultiplier tubes and array detectors. Lists 15 references. (YP)
Sensitive characterization of polyphenolic antioxidants in Polygonatum odoratum by selective solid phase extraction and high performance liquid chromatography-diode array detector-quadrupole time-of-flight tandem mass spectrometry.
Hu, Xin; Zhao, Huading; Shi, Shuyun; Li, Hui; Zhou, Xiaoling; Jiao, Feipeng; Jiang, Xinyu; Peng, Dongming; Chen, Xiaoqin
The complexity of natural products always leads to the co-elution of interfering compounds with bioactive compounds, which then has a detrimental effect on structural elucidation. Here, a new method, based on selective solid phase extraction combined with 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) spiking and high performance liquid chromatography-diode array detector-quadrupole time-of-flight tandem mass spectrometry (HPLC-DAD-QTOF-MS/MS), is described for sensitive screening, selective extraction and identification of polyphenolic antioxidants in Polygonatum odoratum. First, 25 polyphenolic antioxidants (1-25) were screened by DPPH spiking with HPLC. Second, polydopamine coated Fe3O4 microspheres (Fe3O4@PDA) were prepared to selectively extract target antioxidants with extraction efficiency from 55% to 100% when the amount of Fe3O4@PDA, extraction time, desorption solvent and time were 10mg, 20min, acetonitrile, and 5min. Third, 25 antioxidants (10 cinnamides and 15 homoisoflavanones) were identified by HPLC-DAD-QTOF-MS/MS. Furthermore, the DPPH scavenging activities of purified compounds (IC50, 1.6-32.8?g/mL) validated the method. Among the identified antioxidants, four of them (12, 13, 18 and 19) were new compounds, four of them (2, 4, 8 and 14) were first obtained from family Liliaceae, five of them (1, 3, 5, 7 and 9) were first reported in genus Polygonatum, while one compound (24) was first identified in this species. The results indicated that the proposed method was an efficient and sensitive approach to explore polyphenolic antioxidants from complex natural products. PMID:25942343
Simultaneous qualitative and quantitative determination of phenolic compounds in Aloe barbadensis Mill by liquid chromatography-mass spectrometry-ion trap-time-of-flight and high performance liquid chromatography-diode array detector.
Wu, Xiaofang; Ding, Wenjing; Zhong, Jiasheng; Wan, Jinzhi; Xie, Zhiyong
An effective and comprehensive method was developed for the simultaneous analysis of phenolic compounds in the dried exudate of Aloe barbadensis Mill by liquid chromatography-mass spectrometry-ion trap-time-of-flight (LCMS-IT-TOF) and high performance liquid chromatography-diode array detector (HPLC-DAD). Qualitative analysis of all the compounds presented in A. barbadensis Mill was performed on LCMS-IT-TOF, and the diagnostic fragmentation patterns of different types of phenolic compounds (chromones, phenyl pyrones, naphthalene derivative, anthrones and anthraquinones) were discussed on the basis of ESI-IT-TOF MS of components in A. barbadensis Mill and eleven authentic standards. Under the optimal HPLC-DAD chromatographic conditions, quantification of 11 typical phenolic compounds in 15 batches of A. barbadensis Mill was achieved on an Agilent TC-C18 column using gradient elution with a solvent system of methanol and water at a flow rate of 1.0mLmin(-1) and detected at 230nm. All calibration curves exhibited good linear relationship (r(2)>0.9991). The relative standard deviation values for intraday precision were less than 2% with accuracies between 98.21% and 104.57%. The recoveries of the eleven analytes ranged from 97.53 to 105.00% with RSDs less than 2%. This is the first simultaneous characterization and quantitative determination of multiple phenolic compounds in A. barbadensis Mill from locally grown cultivars in China by LCMS-IT-TOF and HPLC-DAD, which can be applied to standardize the quality of A. barbadensis Mill and the future design of nutraceutical and cosmetic preparations. PMID:23542732
Qualitative and quantitative analysis of chemical constituents in traditional Chinese medicinal formula Tong-Xie-Yao-Fang by high-performance liquid chromatography/diode array detection/electrospray ionization tandem mass spectrometry.
Yan, Zhixiang; Yang, Xinghao; Wu, Jianbo; Su, Huai; Chen, Chen; Chen, Yin
Tong-Xie-Yao-Fang (TXYF), a famous traditional Chinese medicine formula, has efficient effects on treatment of the diarrhea-predominant irritable bowel syndrome (D-IBS), a disease with high incidence worldwide. However, the active principles for this complex formula have not been fully explored so far. In this paper, high-performance liquid chromatography coupled with diode array detection and electrospray ionization tandem mass spectrometry (HPLC-DAD-ESI-MS/MS) was applied for the qualitative and quantitative analysis of major chemical constituents in TXYF. Two monoterpene glycosides, one chromone and five polymethoxylated flavones were tentatively characterized based on the retention times, UV spectra and MS data. Fifteen compounds were unambiguously identified by comparison with reference standards. Constituents such as lactone and steroidal, which could not be found by single HPLC method due to the low content in the formula, were identified in this paper. Seven compounds (gallic acid, prim-O-?-D-glucosylcimifugin, paeoniflorin, cimifugin, naringin, hesperidin and 4'-O-?-D-glucosyl-5-O-methylvisamminol) were quantified by HPLC-DAD using a C18 column and gradient elution with acetonitrile and water-0.1% formic acid. The method exhibited intra- and inter-day precision of less than 2.35% and 3.14%, respectively. The LODs and the LOQs for the analytes were less than 0.47 and 1.82 ?g ml(-1), respectively. The overall recoveries ranged from 96.82% to 102.47%, with the R.S.D. ranging from 1.17% to 3.94%. These results demonstrated that our present method was effective and reliable for comprehensive quality evaluation of TXYF. Meanwhile, the study might provide the chemical evidence for revealing the material basis of its therapeutic effects. PMID:21458639
Using of liquid chromatography coupled with diode array detector for determination of naphthoquinones in plants and for investigation of influence of pH of cultivation medium on content of plumbagin in Dionaea muscipula.
Babula, Petr; Mikelova, Radka; Adam, Vojtech; Kizek, Rene; Havel, Ladislav; Sladky, Zdenek
The interest of many investigators in naphthoquinones is due to their broad-range of biological actions from phytotoxic to fungicidal. The main aim of this work was to investigate the influence of different pH values of cultivation medium on naphthoquinone content in Dionaea muscipula. For this purpose, we optimized the simultaneous analysis of the most commonly occurring naphthoquinones (1,4-naphthoquinone, lawsone, juglone and plumbagin) by high performance liquid chromatography coupled with diode array detector (HPLC-DAD). The most suitable chromatographic conditions were as follows: mobile phase: 0.1 mol l-1 acetic acid:methanol in ratio of 33:67 (%, v/v), flow rate: 0.75 ml min-1 and temperature: 42 degrees C. Moreover, we looked for the most suitable technique for preparation of plant samples (D. muscipula, Juglans regia, Paulownia tomentosa, Impatience glandulifera, Impatience parviflora, Drosera rotundifolia, Drosera spathulata and Drosera capensis) due to their consequent analysis by HPLC-DAD. It clearly follows from the results obtained that sonication were the most suitable technique for preparation of J. regia plants. We also checked the recoveries of the determined naphthoquinones, which were from 96 to 104%. Finally, we investigated the changes in content of plumbagin in D. muscipula plants according to different pH of cultivation medium. The content increased with increasing pH up to 5 and, then, changed gradually. The lower content of plumbagin at lower pH values was of interest to us. Therefore, we determined the content of this naphthoquinone in the cultivation medium, what has not been studied before. We discovered that the lower tissue content of plumbagin was due to secretion of this naphthoquinone into the cultivation medium. PMID:16765109
Simultaneous determination of phenolic compounds and saponins in quinoa (Chenopodium quinoa Willd) by a liquid chromatography-diode array detection-electrospray ionization-time-of-flight mass spectrometry methodology.
G¾mez-Caravaca, Ana MarĒa; Segura-Carretero, Antonio; Fernßndez-Gutiķrrez, Alberto; Caboni, Maria Fiorenza
A new liquid chromatography methodology coupled to a diode array detector and a time-of-flight mass spectrometer has been developed for the simultaneous determination of phenolic compounds and saponins in quinoa (Chenopodium quinoa Willd). This method has allowed the simultaneous determination of these two families of compounds with the same analytical method for the first time. A fused-core column C18 has been used, and the analysis has been performed in less than 27 min. Both chromatographic and electrospray ionization time-of-flight mass spectrometry parameters have been optimized to improve the sensitivity and to maximize the number of compounds detected. A validation of the method has also been carried out, and free and bound polar fractions of quinoa have been studied. Twenty-five compounds have been tentatively identified and quantified in the free polar fraction, while five compounds have been tentatively identified and quantified in the bound polar fraction. It is important to highlight that 1-O-galloyl-?-D-glucoside, acacetin, protocatechuic acid 4-O-glucoside, penstebioside, ethyl-m-digallate, (epi)-gallocatechin, and canthoside have been tentatively identified for the first time in quinoa. Free phenolic compounds have been found to be in the range of 2.746-3.803 g/kg of quinoa, while bound phenolic compounds were present in a concentration that varies from 0.139 and 0.164 g/kg. Indeed, saponins have been found to be in a concentration that ranged from 5.6 to 7.5% of the total composition of whole quinoa flour. PMID:21905641
Single-Laboratory Validation of a High-Performance Liquid Chromatographic-Diode Array Detector-Fluorescence Detector/Mass Spectrometric Method for Simultaneous Determination of Water-Soluble Vitamins in Multivitamin Dietary Tablets
Chen, Pei; Atkinson, Renata; Wolf, Wayne R.
The purpose of this study was to develop a single-laboratory validated (SLV) method using high-performance liquid chromatography with different detectors [diode array detector (DAD); fluorescence detector (FLD); and mass spectrometry (MS)] for determination of 7 B-complex vitamins (B1-thiamin, B2-riboflavin, B3-nicotinamide, B6-pyridoxine, B9-folic acid, pantothenic acid, and biotin) and vitamin C in multivitamin/multimineral dietary supplements. The method involves the use of a reversed-phase octadecylsilyl column (4 Ąm, 250 ū 2.0 mm id) and a gradient mobile phase profile. Gradient elution was performed at a flow rate of 0.25 mL/min. After a 5 min isocratic elution at 100% A (0.1% formic acid in water), a linear gradient to 50% A and 50% B (0.1% formic acid in acetonitrile) at 15 min was employed. Detection was performed with a DAD as well as either an FLD or a triple-quadrupole MS detector in the multiple reaction monitoring mode. SLV was performed using Standard Reference Material (SRM) 3280 Multivitamin/Multimineral Tablets, being developed by the National Institute of Standards and Technology, with support by the Office of Dietary Supplements of the National Institutes of Health. Phosphate buffer (10 mM, pH 2.0) extracts of the NIST SRM 3280 were analyzed by the liquid chromatographic (LC)-DAD-FLD/MS method. Following extraction, the method does not require any sample cleanup/preconcentration steps except centrifugation and filtration. PMID:19485230
Single-laboratory validation of a high-performance liquid chromatographic-diode array detector-fluorescence detector/mass spectrometric method for simultaneous determination of water-soluble vitamins in multivitamin dietary tablets.
Chen, Pei; Atkinson, Renata; Wolf, Wayne R
The purpose of this study was to develop a single-laboratory validated (SLV) method using high-performance liquid chromatography with different detectors [diode array detector (DAD); fluorescence detector (FLD); and mass spectrometry (MS)] for determination of 7 B-complex vitamins (B1-thiamin, B2-riboflavin, B3-nicotinamide, B6-pyridoxine, B9-folic acid, pantothenic acid, and biotin) and vitamin C in multivitamin/multimineral dietary supplements. The method involves the use of a reversed-phase octadecylsilyl column (4 microm, 250 x 2.0 mm id) and a gradient mobile phase profile. Gradient elution was performed at a flow rate of 0.25 mL/min. After a 5 min isocratic elution at 100% A (0.1% formic acid in water), a linear gradient to 50% A and 50% B (0.1% formic acid in acetonitrile) at 15 min was employed. Detection was performed with a DAD as well as either an FLD or a triple-quadrupole MS detector in the multiple reaction monitoring mode. SLV was performed using Standard Reference Material (SRM) 3280 Multivitamin/Multimineral Tablets, being developed by the National Institute of Standards and Technology, with support by the Office of Dietary Supplements of the National Institutes of Health. Phosphate buffer (10 mM, pH 2.0) extracts of the NIST SRM 3280 were analyzed by the liquid chromatographic (LC)-DAD-FLDIMS method. Following extraction, the method does not require any sample cleanup/preconcentration steps except centrifugation and filtration. PMID:19485230
Chemometrics-enhanced high performance liquid chromatography-diode array detection strategy for simultaneous determination of eight co-eluted compounds in ten kinds of Chinese teas using second-order calibration method based on alternating trilinear decomposition algorithm.
Yin, Xiao-Li; Wu, Hai-Long; Gu, Hui-Wen; Zhang, Xiao-Hua; Sun, Yan-Mei; Hu, Yong; Liu, Lu; Rong, Qi-Ming; Yu, Ru-Qin
In this work, an attractive chemometrics-enhanced high performance liquid chromatography-diode array detection (HPLC-DAD) strategy was proposed for simultaneous and fast determination of eight co-eluted compounds including gallic acid, caffeine and six catechins in ten kinds of Chinese teas by using second-order calibration method based on alternating trilinear decomposition (ATLD) algorithm. This new strategy proved to be a useful tool for handling the co-eluted peaks, uncalibrated interferences and baseline drifts existing in the process of chromatographic separation, which benefited from the "second-order advantages", making the determination of gallic acid, caffeine and six catechins in tea infusions within 8 min under a simple mobile phase condition. The average recoveries of the analytes on two selected tea samples ranged from 91.7 to 103.1% with standard deviations (SD) ranged from 1.9 to 11.9%. Figures of merit including sensitivity (SEN), selectivity (SEL), root-mean-square error of prediction (RMSEP) and limit of detection (LOD) have been calculated to validate the accuracy of the proposed method. To further confirm the reliability of the method, a multiple reaction monitoring (MRM) method based on LC-MS/MS was employed for comparison and the obtained results of both methods were consistent with each other. Furthermore, as a universal strategy, this new proposed analytical method was applied for the determination of gallic acid, caffeine and catechins in several other kinds of Chinese teas, including different levels and varieties. Finally, based on the quantitative results, principal component analysis (PCA) was used to conduct a cluster analysis for these Chinese teas. The green tea, Oolong tea and Pu-erh raw tea samples were classified successfully. All results demonstrated that the proposed method is accurate, sensitive, fast, universal and ideal for the rapid, routine analysis and discrimination of gallic acid, caffeine and catechins in Chinese tea samples. PMID:25223614
High-speed counter-current chromatography coupled online to high performance liquid chromatography-diode array detector-mass spectrometry for purification, analysis and identification of target compounds from natural products.
Liang, Xuejuan; Zhang, Yuping; Chen, Wei; Cai, Ping; Zhang, Shuihan; Chen, Xiaoqin; Shi, Shuyun
A challenge in coupling high-speed counter-current chromatography (HSCCC) online with high performance liquid chromatography (HPLC) for purity analysis was their time incompatibility. Consequently, HSCCC-HPLC was conducted by either controlling HPLC analysis time and HSCCC flow rate or using stop-and-go scheme. For natural products containing compounds with a wide range of polarities, the former would optimize experimental conditions, while the latter required more time. Here, a novel HSCCC-HPLC-diode array detector-mass spectrometry (HSCCC-HPLC-DAD-MS) was developed for undisrupted purification, analysis and identification of multi-compounds from natural products. Two six-port injection valves and a six-port switching valve were used as interface for collecting key HSCCC effluents alternatively for HPLC-DAD-MS analysis and identification. The ethyl acetate extract of Malus doumeri was performed on the hyphenated system to verify its efficacy. Five main flavonoids, 3-hydroxyphloridzin (1), phloridzin (2), 4',6'-dihydroxyhydrochalcone-2'-O-?-D-glucopyranoside (3, first found in M. doumeri), phloretin (4), and chrysin (5), were purified with purities over 99% by extrusion elution and/or stepwise elution mode in two-step HSCCC, and 25mM ammonium acetate solution was selected instead of water to depress emulsification in the first HSCCC. The online system shortened manipulation time largely compared with off-line analysis procedure and stop-and-go scheme. The results indicated that the present method could serve as a simple, rapid and effective way to achieve target compounds with high purity from natural products. PMID:25678319
Scaling of diode-pumped Cs laser: transverse pump, unstable cavity, MOPA
B. V. Zhdanov; M. K. Shaffer; R. J. Knize
There has been recent interest in Diode Pumped Alkali Lasers (DPALs) and their scaling to higher powers. Scaling of DPALs to high powers requires using multiple pump sources such as laser diode arrays or stacks of arrays. Coupling of multiple pump beams into the laser gain medium can be realized using a transverse pumping scheme that is most efficient for
Optical Spectroscopy Results for the Self-Magnetic Pinch Electron Beam Diode on the ITS-6 Accelerator.
Johnston, Mark D.; Oliver, Bryan V.; Hahn, Kelly; Droemer, Darryl W.; Crain, Marlon D.; Welch, Dale R.; Yitzhak, Maron
Experiments have been conducted at Sandia National Laboratories' RITS-6 accelerator facility [1] (operating at 7.5 MV and 180 kA) investigating plasma formation and propagation in relativistic electron beam diodes used for flash x-ray radiography. High resolution, visible and ultraviolet spectra were collected in the anode-cathode (A-K) vacuum gap of the Self-Magnetic Pinch (SMP) diode [2-4]. Time and space resolved spectra are compared with time-dependent, collisional-radiative (CR) calculations [5-7] and Lsp, hybrid particle-in-cell code simulations [8,9]. Results indicate the presence of a dense (>1x1017cm-3), low temperature (few eV), on-axis plasma, composed of hydrocarbon and metal ion species, which expands at a rate of several cm/s from the anode to the cathode. In addition, cathode plasmas are observed which extend several millimeters into the A-K gap [10]. It is believed that the interaction of these electrode plasmas cause premature impedance collapse of the diode and subsequent reduction in the total radiation output. Diagnostics include high speed imaging and spectroscopy using nanosecond gated ICCD cameras, streak cameras, and photodiode arrays.
GaN Nanorod Schottky and p-n Junction Diodes
Parijat Deb; Hogyoung Kim; Yexian Qin; Roya Lahiji; Mark Oliver; Ronald Reifenberger; Timothy Sands
Conductive atomic force microscopy has been used to characterize single GaN nanorod Schottky and p-n junction diodes. The ideality factor, reverse breakdown voltage, and the Schottky barrier height of individual nanorod diodes were compared to those from conventional thin-film diodes. Large-area contacts, enabling diodes with arrays of GaN nanorods in parallel, were also fabricated and their electrical characteristics investigated. The
Method for extreme ultraviolet lithography
Felter, T. E. (Livermore, CA); Kubiak, Glenn D. (Livermore, CA)
A method of producing a patterned array of features, in particular, gate apertures, in the size range 0.4-0.05 .mu.m using projection lithography and extreme ultraviolet (EUV) radiation. A high energy laser beam is used to vaporize a target material in order to produce a plasma which in turn, produces extreme ultraviolet radiation of a characteristic wavelength of about 13 nm for lithographic applications. The radiation is transmitted by a series of reflective mirrors to a mask which bears the pattern to be printed. The demagnified focused mask pattern is, in turn, transmitted by means of appropriate optics and in a single exposure, to a substrate coated with photoresists designed to be transparent to EUV radiation and also satisfy conventional processing methods.
Method for extreme ultraviolet lithography
Felter, T. E. (727 Clara St., Livermore, Alameda County, CA 94550); Kubiak, G. D. (475 Maple St., Livermore, Alameda County, CA 94550)
A method of producing a patterned array of features, in particular, gate apertures, in the size range 0.4-0.05 .mu.m using projection lithography and extreme ultraviolet (EUV) radiation. A high energy laser beam is used to vaporize a target material in order to produce a plasma which in turn, produces extreme ultraviolet radiation of a characteristic wavelength of about 13 nm for lithographic applications. The radiation is transmitted by a series of reflective mirrors to a mask which bears the pattern to be printed. The demagnified focused mask pattern is, in turn, transmitted by means of appropriate optics and in a single exposure, to a substrate coated with photoresists designed to be transparent to EUV radiation and also satisfy conventional processing methods.
A ZnO nanorod inorganic/organic heterostructure light-emitting diode emitting at 342 nm.
Sun, X W; Huang, J Z; Wang, J X; Xu, Z
An inorganic/organic heterostructure light-emitting diode consisting of the hole-transporting layer N, N'-di(naphth-2-yl)- N, N'-diphenylbenzidine (NPB) and n-type ZnO nanorods fabricated by hydrothermal decomposition is reported. Poly(methyl methacrylate) was used to form a smooth surface on top of ZnO nanorod array with ZnO nanorod tops exposed for subsequent NPB deposition. An unusual ultraviolet emission at 342 nm was observed in the electroluminescence spectrum. Compared to band gap energy of ZnO (3.37 eV), the excitonic emission is blue-shifted and broadened. The mechanism of the blue shift is discussed in terms of the energy band diagram of the heterostructure. PMID:18348540
Photovoltaic array loss mechanisms
NASA Technical Reports Server (NTRS)
Gonzalez, Charles
Loss mechanisms which come into play when solar cell modules are mounted in arrays are identified. Losses can occur either from a reduction in the array electrical performance or with nonoptimal extraction of power from the array. Electrical performance degradation is caused by electrical mismatch, transmission losses from cell surface soiling and steep angle of reflectance, and electrical losses from field wiring resistance and the voltage drop across blocking diodes. The second type of loss, concerned with the operating points of the array, can involve nonoptimal load impedance and limiting the operating envelope of the array to specific ranges of voltage and current. Each of the loss mechanisms are discussed and average energy losses expected from soiling, steep reflectance angles and circuit losses are calculated.
Photovoltaic array loss mechanisms
NASA Astrophysics Data System (ADS)
Gonzalez, Charles
Loss mechanisms which come into play when solar cell modules are mounted in arrays are identified. Losses can occur either from a reduction in the array electrical performance or with nonoptimal extraction of power from the array. Electrical performance degradation is caused by electrical mismatch, transmission losses from cell surface soiling and steep angle of reflectance, and electrical losses from field wiring resistance and the voltage drop across blocking diodes. The second type of loss, concerned with the operating points of the array, can involve nonoptimal load impedance and limiting the operating envelope of the array to specific ranges of voltage and current. Each of the loss mechanisms are discussed and average energy losses expected from soiling, steep reflectance angles and circuit losses are calculated.
Qualification and Selection of Flight Diode Lasers for Space Applications
NASA Technical Reports Server (NTRS)
Liebe, Carl C.; Dillon, Robert P.; Gontijo, Ivair; Forouhar, Siamak; Shapiro, Andrew A.; Cooper, Mark S.; Meras, Patrick L.
The reliability and lifetime of laser diodes is critical to space missions. The Nuclear Spectroscopic Telescope Array (NuSTAR) mission includes a metrology system that is based upon laser diodes. An operational test facility has been developed to qualify and select, by mission standards, laser diodes that will survive the intended space environment and mission lifetime. The facility is situated in an electrostatic discharge (ESD) certified clean-room and consist of an enclosed temperature-controlled stage that can accommodate up to 20 laser diodes. The facility is designed to characterize a single laser diode, in addition to conducting laser lifetime testing on up to 20 laser diodes simultaneously. A standard laser current driver is used to drive a single laser diode. Laser diode current, voltage, power, and wavelength are measured for each laser diode, and a method of selecting the most adequate laser diodes for space deployment is implemented. The method consists of creating histograms of laser threshold currents, powers at a designated current, and wavelengths at designated power. From these histograms, the laser diodes that illustrate a performance that is outside the normal are rejected and the remaining lasers are considered spaceborne candidates. To perform laser lifetime testing, the facility is equipped with 20 custom laser drivers that were designed and built by California Institute of Technology specifically to drive NuSTAR metrology lasers. The laser drivers can be operated in constant-current mode or alternating-current mode. Situated inside the enclosure, in front of the laser diodes, are 20 power-meter heads to record laser power throughout the duration of lifetime testing. Prior to connecting a laser diode to the current source for characterization and lifetime testing, a background program is initiated to collect current, voltage, and resistance. This backstage data collection enables the operational test facility to have full laser diode traceablity.
Simultaneous determination of 10 components in Bu-Zhong-Yi-Qi Wan by solid phase extraction-high performance liquid chromatography with diode array detection and evaporative light scattering detection.
Hu, Fang; Zhu, Ruijuan; Liu, Xiaohua; Yang, Yinglai; Li, Can; Feng, Shilan; Li, Yingdong
An effective, accurate and reliable method for the simultaneous separation and determination of 10 major components in Chinese medicine Bu-Zhong-Yi-Qi Wan (BZYQW) was developed and validated using solid phase extraction column-high performance liquid chromatography-diode array detection-evaporative light scattering detection (SPE-HPLC-DAD-ELSD). The chromatographic separation was performed on a SpursilÖ C18 column (250 mm ū 4.6 mm, 5 Ąm) at 30░C with an acetonitrile-water gradient as mobile phase. The DAD detection wavelength 254 nm was utilized for the quantitative analysis. The drift tube temperature and the carrier gas flow rate of the ELSD detection was set at 110.5░C and 3.1 mL/min. The total run time is 103 min, these determined components peak out within 81 min. Excellent linear behaviors over the investigated concentration ranges were observed with the values of r(2) higher than 0.9990 for all the analytes. The Linear range over hesperidin, senkyunolide I, senkyunolide H, ononin, calycosin, formononetin, ligustilide, butylene phthalide, astragaloside IV, astragaloside I is 4.50-94.50 Ąg/mL, 22.75-364.00 Ąg/mL, 2.30-45.00 Ąg/mL, 11.76-125.14 Ąg/mL, 4.62-50.35 Ąg/mL, 1.90-28.93 Ąg/mL, 1.29-159.00 Ąg/mL, 2.90-36.00 Ąg/mL, 35.40-192.40 Ąg/mL, 41.40-96.60 Ąg/mL, respectively. The method was validated by its repeatability [relative standard deviation (RSD) < 3.54%] and intra-day (RSD < 2.11%) and inter-day precision (RSD < 3.45%). The limits of detection and quantification of each component were in the ranges of 0.04-10.24 and 0.12-39.22 Ąg/mL, respectively. The average recovery yields of the 10 compounds ranged from 95.79 to 101.25%. The validated method was successfully applied to the simultaneous determination of these principal components in 10 commercial samples of BZYQW from different manufacturers. PMID:25214498
Photoluminescence properties and energy transfer in Ce(3+) /Dy(3+) co-doped Sr(3) MgSi(2) O(8) phosphors for potential application in ultraviolet white light-emitting diodes.
Yu, Hong; Zi, Wenwen; Lan, Shi; Gan, Shucai; Zou, Haifeng; Xu, Xuechun; Hong, Guangyan
Sr(3) MgSi(2) O(8) :Ce(3+) , Dy(3+) phosphors were prepared by a solid-state reaction technique and the photoluminescence properties were investigated. The emission spectra show not only a band due to Ce(3+) ions (403?nm) but also as a band due to Dy(3+) ions (480, 575?nm) (UV light excitation). The photoluminescence properties reveal that effective energy transfer occurs in Ce(3+) /Dy(3+) co-doped Sr(3) MgSi(2) O(8)phosphors, and the co-doping of Ce(3+) could enhance the emission intensity of Dy(3+) to a certain extent by transferring its energy to Dy(3+) . The Ce(3+) /Dy(3+) energy transfer was investigated by emission/excitation spectra, and photoluminescence decay behaviors. In Sr2.94 MgSi2 O8 :0.01Ce(3+) , 0.05Dy(3+) phosphors, the fluorescence lifetime of Dy(3+) (from 3.35 to 27.59?ns) is increased whereas that of Ce(3+) is greatly decreased (from 43.59 to 13.55?ns), and this provides indirect evidence of the Ce(3+) to Dy(3+) energy transfer. The varied emitted color of Sr(3) MgSi(2) O(8):Ce(3+) , Dy(3+) phosphors from blue to white were achieved by altering the concentration ratio of Ce(3+) and Dy(3+) . These results indicate Sr(3) MgSi(2) O(8):Ce(3+) , Dy(3+) may be as a candidate phosphor for white light-emitting diodes. PMID:22987772
Energy transfer from Sm3+ to Eu3+ in red-emitting phosphor LaMgAl11O19:Sm3+, Eu3+ for solar cells and near-ultraviolet white light-emitting diodes.
Min, Xin; Huang, Zhaohui; Fang, Minghao; Liu, Yan-Gai; Tang, Chao; Wu, Xiaowen
The red-emitting phosphor LaMgAl11O19:Sm(3+), Eu(3+) was prepared by solid-state reaction at 1600 ░C for 4 h. The phase formation, luminescence properties, and energy transfer from Sm(3+) to Eu(3+) were studied. With the addition of 5 mol % Sm(3+) as the sensitizer, the excitation wavelength of LaMgAl11O19:Eu(3+) phosphor was extended from 464 to 403 nm, and the emission intensity under the excitation at 403 nm was also enhanced. The host material LaMgAl11O19 could contain the high doping content of Eu(3+) (20 mol %) without concentration quenching. This energy transfer from Sm(3+) to Eu(3+) was confirmed by the decay times of energy donor Sm(3+). The mechanism of energy transfer (Sm(3+) ? Eu(3+)) was proved to be quadrupole-quadrupole interaction. Under the 403 nm excitation at 150 ░C, the emission intensities of the characteristic peaks of Sm(3+) and Eu(3+) in LaMgAl11O19:0.05Sm(3+), 0.2Eu(3+) phosphor were decreased to 65% and 56% of the initial intensities at room temperature, and the relatively high activation energy proved that this phosphor had a good thermal stability. The CIE coordinate was calculated to be (x = 0.601, y = 0.390). The LaMgAl11O19:0.05Sm(3+), 0.2Eu(3+) phosphor is a candidate for copper phthalocyanine-based solar cells and white light-emitting diodes. PMID:24884208
A room temperature flip-chip mounting technique for laser diodes on silicon motherboards
L. Vanwassenhove; P. Van Daele
In this presentation, a relatively simple mounting method is suggested for flip-chip mounting of arrays of edge-emitting laser diodes to arrays of fibers. What really makes the difference with known methods is the use of a room temperature mounting process using a transparent UV-curing, non conducting glue for the fixation of arrays of laser diodes. Apart from power budget problems,
Diode and Diode Circuits, a Programmed Text.
ERIC Educational Resources Information Center
Balabanian, Norman; Kirwin, Gerald J.
This programed text on diode and diode circuits was developed under contract with the United States Office of Education as Number 4 in a series of materials for use in an electrical engineering sequence. It is intended as a supplement to a regular text and other instructional material. (DH)
Ultraviolet O2 transmittance - AURIC implementation
NASA Technical Reports Server (NTRS)
Anderson, G. P.; Hall, L. A.; Minschwaner, K.; Yoshino, K.; Betchley, C.; Conant, J. A.
A new spectrally precise approach to Schumann-Runge synthesis has been devised, employing nine (9) different spectral arrays containing polynomial coefficients. The coefficients were fit to calculated cross sections obtained from a detailed Schumann-Runge model that incorporates the most recent high resolution spectroscopic data for a temperature range between 130 and 500K. This large data base is being used to reexamine the existing parameterizations of UV transmission and photolysis. In addition, it is now possible to extend atmospheric radiance codes further into the ultraviolet. Initial implementation has been accomplished for the MODTRAN code as part of the eventual development of AURIC, the Atmospheric Ultraviolet Radiance Integrated Code.
Confirmation of malachite green, gentian violet and their leuco analogs in catfish and trout tissue by high-performance liquid chromatography utilizing electrochemistry with ultraviolet-visible diode array detection and fluorescence detection
Larry G. Rushing; Eugene B. Hansen
A sensitive analytical procedure for the confirmation of residues of malachite green (MG), gentian violet (GV) and their leuco analogs (LMG and LGV) in catfish and trout tissue at 10 ng\\/g is described. Frozen (?20░C) fish fillets were cut into small pieces and homogenized in Waring blendors. The compounds of interest were extracted from 20-g amounts of homogenized fish tissue
High power diode lasers for solid-state laser pumps
Kurt J. Linden; Patrick N. McDonnell
The development and commercial application of high power diode laser arrays for use as solid-state laser pumps is described. Such solid-state laser pumps are significantly more efficient and reliable than conventional flash-lamps. This paper describes the design and fabrication of diode lasers emitting in the 780 - 900 nm spectral region, and discusses their performance and reliability. Typical measured performance
Photoresist composition for extreme ultraviolet lithography
Felter, T. E. (Alameda County, CA); Kubiak, G. D. (Alameda County, CA)
A method of producing a patterned array of features, in particular, gate apertures, in the size range 0.4-0.05 .mu.m using projection lithography and extreme ultraviolet (EUV) radiation. A high energy laser beam is used to vaporize a target material in order to produce a plasma which in turn, produces extreme ultraviolet radiation of a characteristic wavelength of about 13 nm for lithographic applications. The radiation is transmitted by a series of reflective mirrors to a mask which bears the pattern to be printed. The demagnified focused mask pattern is, in turn, transmitted by means of appropriate optics and in a single exposure, to a substrate coated with photoresists designed to be transparent to EUV radiation and also satisfy conventional processing methods. A photoresist composition for extreme ultraviolet radiation of boron carbide polymers, hydrochlorocarbons and mixtures thereof.
The Junction Diode Basic Operation
Leach Jr.,W. Marshall
The Junction Diode Basic Operation The diode is fabricated of a semiconductor material, usually section of the diode. The junction is the dividing line between the n-type and p-type sides. Thermal the electric field sweeps them out. Figure 1: (a) Diode cross section. (b) Reverse biased diode. (c) Forward
Fast, High-Precision Readout Circuit for Detector Arrays
NASA Technical Reports Server (NTRS)
Rider, David M.; Hancock, Bruce R.; Key, Richard W.; Cunningham, Thomas J.; Wrigley, Chris J.; Seshadri, Suresh; Sander, Stanley P.; Blavier, Jean-Francois L.
The GEO-CAPE mission described in NASA's Earth Science and Applications Decadal Survey requires high spatial, temporal, and spectral resolution measurements to monitor and characterize the rapidly changing chemistry of the troposphere over North and South Americas. High-frame-rate focal plane arrays (FPAs) with many pixels are needed to enable such measurements. A high-throughput digital detector readout integrated circuit (ROIC) that meets the GEO-CAPE FPA needs has been developed, fabricated, and tested. The ROIC is based on an innovative charge integrating, fast, high-precision analog-to-digital circuit that is built into each pixel. The 128ū128-pixel ROIC digitizes all 16,384 pixels simultaneously at frame rates up to 16 kHz to provide a completely digital output on a single integrated circuit at an unprecedented rate of 262 million pixels per second. The approach eliminates the need for off focal plane electronics, greatly reducing volume, mass, and power compared to conventional FPA implementations. A focal plane based on this ROIC will require less than 2 W of power on a 1ū1-cm integrated circuit. The ROIC is fabricated of silicon using CMOS technology. It is designed to be indium bump bonded to a variety of detector materials including silicon PIN diodes, indium antimonide (InSb), indium gallium arsenide (In- GaAs), and mercury cadmium telluride (HgCdTe) detector arrays to provide coverage over a broad spectral range in the infrared, visible, and ultraviolet spectral ranges.
A transparent ultraviolet triggered amorphous selenium p-n junction
NASA Astrophysics Data System (ADS)
Saito, Ichitaro; Miyazaki, Wataru; Onishi, Masanori; Kudo, Yuki; Masuzawa, Tomoaki; Yamada, Takatoshi; Koh, Angel; Chua, Daniel; Soga, Kenichi; Overend, Mauro; Aono, Masami; Amaratunga, Gehan A. J.; Okano, Ken
This paper will introduce a semitransparent amorphous selenium (a-Se) film exhibiting photovoltaic effects under ultraviolet light created through a simple and inexpensive method. We found that chlorine can be doped into a-Se through electrolysis of saturated salt water, and converts the weak p-type material into an n-type material. Furthermore, we found that a p-n diode fabricated through this process has shown an open circuit voltage of 0.35 V toward ultraviolet illumination. Our results suggest the possibility of doping control depending on the electric current during electrolysis and the possibility of developing a simple doping method for amorphous photoconductors.
Study on the digitized and quantified evaluating method for the super information cluster of traditional Chinese medicine ultraviolet spectral fingerprints
Li, Lifeng; Liu, Zhongbo; Li, Yanfei
The theories of ultraviolet spectral fingerprint (UVFP) index, information index, fluctuation index, information fluctuation index combined with the quantified UV fingerprint method (QUFM) had been established and put into practice in the Ginkgo Tablets (GT) quality evaluation. The flowing injection analysis (FIA) coupled with a diode array detector was applied as a novel method to obtain the UVFP in the region of 190-400 nm at which the absorption can reflect all the information of the chemical constituents contained ???*, n??* and n??* transition. The result showed that all batches were qualified (Grade ?3) except S8 for its too high contents. It was proved that this method made the expression of superposed information in UVFP of traditional Chinese medicine (TCM) digitized and simple. WhatÆs more, an approach which can test the total chemical content with the chromophoric characteristics in the complex system of TCM rapidly, simply and accurately was achieved by the application of QUFM. In one word, it made the exploration of the general characteristic information of the molecular absorption complex TCM in the ultraviolet regions feasible and possible. PMID:25332974
A 15 element focal plane array for 100 GHz
Neal R. Erickson; Paul F. Goldsmith; G. Novak; Ronald M. Grosslein; P. J. Viscuso; Ronna B. Erickson; C. R. Predmore
A focal plane imaging array receiver is described which covers the 86-115 GHz frequency range for radio astronomical observations. The 3 x 5 element array uses cryogenic Schottky diode mixers with integrated HEMT IF amplifiers. A cold quasi-optical filter selects the desired sideband, and terminates the image at 20 K. Polarization interleaving is used to minimize the array size on
Diode-pumped 10 W continuous wave cesium laser.
Zhdanov, Boris; Knize, R J
An efficient cesium vapor laser pumped with a continuous wave laser diode array has been demonstrated. The linewidth of the pump source was narrowed using the external cavity to match it to the cesium absorption line. The output power of the continuous wave cesium laser was 10 W, which exceeds previous results by more than a factor of 10, and the slope efficiency was 68%. The overall optical efficiency was 62%, which is a factor of 6 higher than previous pulsed laser results for alkali lasers with diode laser array pumping. PMID:17671572
NASA Astrophysics Data System (ADS)
Kong, Long; Liu, QingXiang; Li, XiangQiang; Wang, ShaoMeng
A kind of coaxial foilless diode is proposed in this paper, with the structure model and operating principle of the diode are given. The current-voltage relation of the coaxial foilless diode and the effects of structure parameters on the relation are studied by simulation. By solving the electron motion equation, the beam deviation characteristic in the presence of external magnetic field in transmission process is analyzed, and the relationship between transverse misalignment with diode parameters is obtained. These results should be of interest to the area of generation and propagation of radial beam for application of generating high power microwaves.
NSDL National Science Digital Library
Kuphaldt, Tony R.
Written by Tony R. Kuphaldt, this chapter of All About Circuit's third volume on Semiconductors describes the physics behind diodes and rectifiers. The chapter is divided into fourteen sections on topics including diode ratings, voltage multipliers, and zener diodes. Each section has clear illustrations and examples, and most have a concise, bulleted review of what was covered at the end of the page. This is an excellent resource for educators in physics and electronic engineering classrooms to introduce lessons or units on semiconductors, diodes, and rectifiers. [ASC
Kong, Long; Liu, QingXiang; Li, XiangQiang; Wang, ShaoMeng [College of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031 (China)] [College of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031 (China)
A kind of coaxial foilless diode is proposed in this paper, with the structure model and operating principle of the diode are given. The current-voltage relation of the coaxial foilless diode and the effects of structure parameters on the relation are studied by simulation. By solving the electron motion equation, the beam deviation characteristic in the presence of external magnetic field in transmission process is analyzed, and the relationship between transverse misalignment with diode parameters is obtained. These results should be of interest to the area of generation and propagation of radial beam for application of generating high power microwaves.
A Frequency-Agile Compact Array With a Reconfigurable Decoupling and Matching Network
Yong Cai; Y. Jay Guo
A new frequency-agile compact antenna array incorporating a reconfigurable decoupling and matching net- work (DMN) is presented. The array consists of two printed monopole antennas, each loaded with a p-i-n diode. By changing the p-i-n diode states through an inductive biasing line, the array operating frequency can be tuned to the 2.5- or 3.5-GHz band. The array interelement spacing is
Advances in bonding technology for high power diode laser bars
NASA Astrophysics Data System (ADS)
Wang, Jingwei; Li, Xiaoning; Hou, Dong; Feng, Feifei; Liu, Yalong; Liu, Xingsheng
Due to their high electrical-optical conversion efficiency, compact size and long lifetime, high power diode lasers have found increased applications in many fields. As the improvement of device technology, high power diode laser bars with output power of tens or hundreds watts have been commercially available. With the increase of high current and output power, the reliability and lifetime of high power diode laser bars becomes a challenge, especially under harsh working conditions and hard-pulse operations. The bonding technology is still one of the bottlenecks of the advancement of high power diode laser bars. Currently, materials used in bonding high power diode laser bars are commonly indium and goldtin solders. Experimental and field application results indicates that the lifetime and reliability of high power diode laser bars bonded by gold-tin solder is much better than that bonded by indium solder which is prone to thermal fatigue, electro-migration and oxidization. In this paper, we review the bonding technologies for high power diode laser bars and present the advances in bonding technology for single bars, horizontal bar arrays and vertical bar stacks. We will also present the challenges and issues in bonding technology for high power diode laser bars and discuss some approaches and strategies in addressing the challenges and issues.
GaAs Schottky varactor diode optimization for high-performance nonlinear transmission lines
D. Sawdai; D. Ko; M. Kintis; S. Maas; X. Zhang; S. Valdes; E. Garber; G. Barber; E. Quach; J. Newman; F. Fong
Nonlinear transmission lines (NLTLs) using Schottky diodes as varactor loads provide significant performance and efficiency advantages for both frequency multiplication and phase shifting applications that will benefit comb generator and phased array applications, respectively. Prior NLTL optimization has been limited only to analytical studies of specific diode profiles. This paper describes, for the first time, the optimization of NLTL performance
Semiconductor for the Green Multi-Bit Gated-Diode Flash Memory
Lee, Jong Duk
density flash memory application [1],[2]. As illustrated in Fig. 1, the memory array scheme is similar, the gated- diode non-volatile memory has no channel but the gate just controls the tunneling current of the pn junction diode. Therefore, further scaling of the gate length is possible as it is not suffering
Fabrication of GaN Schottky Barrier Diodes for UV Detectors (abstract)
M. Diale
Schottky barrier diodes have been studied for the optimization of GaN-based ultraviolet detectors. Surface preparation prior to device fabrication has been found to influence the performance of the contacts. Ni\\/Au contact was found to reduce surface oxide, resulting in improved electrical parameters for the Schottky diode. It has been found that Au metal contact on GaN gave better electrical characteristics
Low-power ultraviolet lidar for standoff detection of BW agents
Coorg R. Prasad; Wen Huang; Jack Bufton; Alexander Achey; Jeffrey Dawson; Robert M. Serino; Wenhui Shi
A compact ultraviolet lidar stand-off sensor was recently developed and field-tested for detection of bio warfare (BW) agent stimulant aerosols and interferents. It employed a low-power (~5mW), continuous-wave, 375nm semiconductor ultraviolet optical source (SUVOS) laser diode that was modulated at high-speed with a pseudo-random (PR) code to provide range-resolved lidar detection of both aerosol elastic scattering and fluorescence. The sensor
Ultraviolet absorption spectrum of HOCl
NASA Technical Reports Server (NTRS)
Burkholder, James B.
The room temperature UV absorption spectrum of HOCl was measured over the wavelength range 200 to 380 nm with a diode array spectrometer. The absorption spectrum was identified from UV absorption spectra recorded following UV photolysis of equilibrium mixtures of Cl2O/H2O/HOCl. The HOCl spectrum is continuous with a maximum at 242 nm and a secondary peak at 304 nm. The measured absorption cross section at 242 nm was (2.1 +/- 0.3) x 10 exp -19/sq cm (2 sigma error limits). These results are in excellent agreement with the work of Knauth et al. (1979) but in poor agreement with the more recent measurements of Mishalanie et al. (1986) and Permien et al. (1988). An HOCl nu2 infrared band intensity of 230 +/- 35/sq cm atm was determined based on this UV absorption cross section. The present results are compared with these previous measurements and the discrepancies are discussed.
Ultraviolet absorption spectrum of chlorine peroxide, ClOOCl.
Pope, Francis D; Hansen, Jaron C; Bayes, Kyle D; Friedl, Randall R; Sander, Stanley P
The photolysis of chlorine peroxide (ClOOCl) is understood to be a key step in the destruction of polar stratospheric ozone. This study generated and purified ClOOCl in a novel fashion, which resulted in spectra with low impurity levels and high peak absorbances. The ClOOCl was generated by laser photolysis of Cl2 in the presence of ozone, or by photolysis of ozone in the presence of CF2Cl2. The product ClOOCl was collected, along with small amounts of impurities, in a trap at about -125 degrees C. Gas-phase ultraviolet spectra were recorded using a long path cell and spectrograph/diode array detector as the trap was slowly warmed. The spectrum of ClOOCl could be fit with two Gaussian-like expressions, corresponding to two different electronic transitions, having similar energies but different widths. The energies and band strengths of these two transitions compare favorably with previous ab initio calculations. The cross sections of ClOOCl at wavelengths longer than 300 nm are significantly lower than all previous measurements or estimates. These low cross sections in the photolytically active region of the solar spectrum result in a rate of photolysis of ClOOCl in the stratosphere that is much lower than currently recommended. For conditions representative of the polar vortex (solar zenith angle of 86 degrees, 20 km altitude, and O3 and temperature profiles measured in March 2000) calculated photolysis rates are a factor of 6 lower than the current JPL/NASA recommendation. This large discrepancy calls into question the completeness of present atmospheric models of polar ozone depletion. PMID:17474723
Eve: Extreme Ultraviolet Variability Experiment
NSDL National Science Digital Library
In this NASA video, scientists describe how the Extreme Ultraviolet Variability Experiment will sample and track the Sun's ultraviolet irradiance, providing a detailed time sequence of extreme ultraviolet output -- data that can provide advance warning for potentially disruptive energy bursts.
Temperature dependent behaviour of 340 nm light emitting diodes incorporating a gallium nitride interlayer
R. J. Airey; K. B. Lee; P. J. Parbrook; J. Bai; F. Ranalli; T. Wang; G. Hill
Ultra-violet light emitting diodes with an increased efficiency have been produced. The increase in efficiency was brought about by the introduction of a thin GaN layer between the AlN buffer and the subsequent AlGaN layers. The GaN interlayer causes a reduction in the number of threading dislocations that propagate through the ultra-violet light emitting structure. Temperature dependent electroluminescence measurements show
P. J. Stabile; B. Lalevic
Conventional IMPATT diodes are the highest-power microwave semiconductor devices, but they are difficult to couple light into, challenging to integrate into monolithic circuits, to incorporate a third terminal, or to series combine. The lateral IMPATT diode is proposed as a solution to these problems. This device is planar and features contact and drift regions that are all adjacent to the
NASA Technical Reports Server (NTRS)
Deters, R. A.
Small-signal diodes are placed in series with light-emitting diodes (LED's) to stabilize LED output against temperature fluctuations. Simple inexpensive method compensates for thermal fluctuations over a broad temperature range. Requiring few components, technique is particularly useful where circuit-board space is limited.
Houck, Edward D. (Idaho Falls, ID)
A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other.
Reliability of Deep-UV Light-Emitting Diodes
Matteo Meneghini; Maura Pavesi; Nicola Trivellin; Remis Gaska; Enrico Zanoni; Gaudenzio Meneghesso
This paper analyzes the performance and reliability of deep-ultraviolet light-emitting diodes (LEDs) on AlGaN emitting at 280 and 295 nm. By means of detailed electroluminescence characterization, we show that the optical properties of the LEDs are strongly influenced by the presence of deep-level-related radiative transitions, and we separately evaluate the contribution of each of these recombination mechanisms on the overall
Versatile multispectral microscope based on light emitting diodes
NASA Astrophysics Data System (ADS)
Brydegaard, Mikkel; Merdasa, Aboma; Jayaweera, Hiran; ┼lebring, Jens; Svanberg, Sune
We describe the development of a novel multispectral microscope, based on light-emitting diodes, capable of acquiring megapixel images in thirteen spectral bands from the ultraviolet to the near infrared. The system captures images and spectra in transmittance, reflectance, and scattering modes. We present as examples of applications ground truth measurements for remote sensing and parasitology diagnostics. The system is a general purpose scientific instrument that could be used to develop dedicated simplified instruments with optimal bands and mode selection.
D. N. Lambert; R. H. Bennett
An ultraviolet water purifier has a number of ultraviolet lamps mounted in a cover which extends over the purifier and above the water. A parabolic reflector directs the rays of the lamps toward the body of water. The purifier is provided with a water inlet and a baffle adjacent to it having an opening at its base to compel the
Ultraviolet Complete Quantum Gravity
J. W. Moffat
An ultraviolet complete quantum gravity theory is formulated in which vertex functions in Feynman graphs are entire functions and the propagating graviton is described by a local, causal propagator. The cosmological constant problem is investigated in the context of the ultraviolet complete quantum gravity.
Nonvolatile Array Of Synapses For Neural Network
NASA Technical Reports Server (NTRS)
Tawel, Raoul
Elements of array programmed with help of ultraviolet light. A 32 x 32 very-large-scale integrated-circuit array of electronic synapses serves as building-block chip for analog neural-network computer. Synaptic weights stored in nonvolatile manner. Makes information content of array invulnerable to loss of power, and, by eliminating need for circuitry to refresh volatile synaptic memory, makes architecture simpler and more compact.
Relativistic Bursian diode equilibria
Ender, A. Y.; Kuznetsov, V. I. [Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation); Schamel, H. [Physikalisches Institut, Universitaet Bayreuth, D-95466 Bayreuth (Germany)
A comprehensive study of steady-states of a planar vacuum diode driven by a cold relativistic electron beam is presented. The emitter electric field as a characteristic function for their existence is evaluated in dependence of the diode length, the applied potential V, and the relativistic beam factor at injection {gamma}{sub 0}. It is used to classify the different branches of possible solutions, which encompass electron flows that are (i) transmitted through the diode completely, (ii) partially reflected from a virtual cathode (VC) either within the diode region or at the collector side, and (iii) reflected totally. As a byproduct, the V and {gamma}{sub 0} dependences of both bifurcation points of the minimum potential and of the transmitted current are obtained and the ultrarelativistic limit, {gamma}{sub 0}>>1, is performed. In this highly relativistic regime, the density of electrons appears to be constant across the diode region except for a small area around the VC.
Ultraviolet absorption experiment MA-059
NASA Technical Reports Server (NTRS)
Donahue, T. M.; Hudson, R. D.; Anderson, J.; Kaufman, F.; Mcelroy, M. B.
The ultraviolet absorption experiment performed during the Apollo Soyuz mission involved sending a beam of atomic oxygen and atomic nitrogen resonance radiation, strong unabsorbable oxygen and nitrogen radiation, and visual radiation, all filling the same 3 deg-wide field of view from the Apollo to the Soyuz. The radiation struck a retroreflector array on the Soyuz and was returned to a spectrometer onboard the Apollo. The density of atomic oxygen and atomic nitrogen between the two spacecraft was measured by observing the amount of resonance radiation absorbed when the line joining Apollo and Soyuz was perpendicular to their velocity with respect to the ambient atmosphere. Information concerning oxygen densities was also obtained by observation of resonantly fluorescent light. The absorption experiments for atomic oxygen and atomic nitrogen were successfully performed at a range of 500 meters, and abundant resonance fluorescence data were obtained.
Dual-band ultraviolet-short-wavelength infrared imaging via luminescent downshifting with colloidal quantum dots
Geyer, Scott M.
The performance of short-wavelength infrared (SWIR) cameras in the visible and ultraviolet (UV) regions is limited by the absorption of high-energy photons in inactive regions of the imaging array. Dual-band UV-SWIR imaging ...
High-power diode lasers for space communications - A review
D. Botez
A development status evaluation is presented for high power, 50-1000 mW diode lasers applicable to space communications; attention is given to current and prospective capabilities of monolithic single-element and few-element devices constituting phase-locked arrays, as well as to various more-than-10-element phase-locked arrays. Nonabsorbing mirror structures are employed to preclude facet degradation. Also noted are the prospects for development of hybrid
Directional control of infrared antenna-coupled tunnel diodes.
Slovick, Brian A; Bean, Jeffrey A; Krenz, Peter M; Boreman, Glenn D
Directional control of received infrared radiation is demonstrated with a phased-array antenna connected by a coplanar strip transmission line to a metal-oxide-metal (MOM) tunnel diode. We implement a MOM diode to ensure that the measured response originates from the interference of infrared antenna currents at specific locations in the array. The reception angle of the antenna is altered by shifting the diode position along the transmission line connecting the antenna elements. By fabricating the devices on a quarter wave dielectric layer above a ground plane, narrow beam widths of 35░ FWHM in power and reception angles of ▒ 50░ are achieved with minimal side lobe contributions. Measured radiation patterns at 10.6 ?m are substantiated by electromagnetic simulations as well as an analytic interference model. PMID:20940991
Diode-pumped 10 W continuous wave cesium laser
Boris Zhdanov; R. J. Knize
An efficient cesium vapor laser pumped with a continuous wave laser diode array has been demonstrated. The linewidth of the pump source was narrowed using the external cavity to match it to the cesium absorption line. The output power of the continuous wave cesium laser was 10 W, which exceeds previous results by more than a factor of 10, and
Ultraviolet absorption hygrometer
Gersh, Michael E. (Bedford, MA); Bien, Fritz (Concord, MA); Bernstein, Lawrence S. (Bedford, MA)
An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined.
Ultraviolet absorption hygrometer
Gersh, M.E.; Bien, F.; Bernstein, L.S.
An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined. 5 figs.
Human exposure to ultraviolet radiation
Passchier, W.F. (Health Council of the Netherlands, The Hague (NL)); Bosnjakovic, B.F.M. (Ministry of Housing, The Hague (NL))
These proceedings contain over 50 selections. Some of the title are: Man and ultraviolet radiation; Effects of ultraviolet radiations on the human skin: emphasis on skin cancer; Human exposure to ultraviolet radiation: Quantitative modelling of skin cancer incidence; Human exposure to ultraviolet radiation: Data; and Share of erythema dose of solar radiation in high mountains.
Ultraviolet-B radiation alters phenolic salicylate and flavonoid composition of Populus trichocarpa leaves.
Warren, Jeffrey M; Bassman, John H; Fellman, John K; Mattinson, D Scott; Eigenbrode, Sanford
We investigated foliar phenolic composition of field- and greenhouse-grown Populus trichocarpa Torr. & A. Gray (black cottonwood) ramets subjected to near zero (0x), ambient (1x) or twice ambient (2x) concentrations of biologically effective ultraviolet-B (UV-B) radiation. After a 3-month treatment period, several age classes of foliage samples were harvested and the phenolic compounds extracted, separated by high performance liquid chromatography and identified and quantified by diode-array spectrometry and mass spectrometry. Foliar phenolic concentration was greater in 1x- and 2x-treated tissue than in 0x-treated tissue. Phenolic compounds that increased in response to UV-B radiation were predominantly flavonoids, primarily quercetin and kaempferol glycosides. Enhancement of UV-B radiation from 1x to 2x ambient concentration did not result in further flavonoid accumulation in either greenhouse or field ramets; however, a non-flavonoid phenolic glycoside, salicortin, increased in response to an increase in UV-B radiation from 1x to 2x ambient concentration. Increased salicortin concentrations accounted for at least 30-40% of the total (5%) increase in UV-absorption potential of 2x-treated tissue. Because salicortin and other salicylates are important in plant-herbivore-predator relationships, these increases are discussed in the context of collateral feeding studies. We conclude that enhanced solar UV-B radiation may significantly alter trophic structure in some ecosystems by stimulating specific phenolic compounds. PMID:12730044
NASA Technical Reports Server (NTRS)
Rutledge, D. B.; Muha, M. S.
Many millimeter and far-infrared imaging systems are limited in sensitivity and speed because they depend on a single scanned element. Because of recent advances in planar detectors such as Schottky diodes, superconducting tunnel junctions, and microbolometers, an attractive approach to this problem is a planar antenna array with integrated detectors. A planar line antenna array and optical system for imaging has been developed. The significant advances are a 'reverse-microscope' optical configuration and a modified bow-tie antenna design. In the 'reverse-microscope' configuration, a lens is attached to the bottom of the substrate containing the antennas. Imaging is done through the substrate. This configuration eliminates the troublesome effects of substrate surface waves. The substrate lens has only a single refracting surface, making possible a virtually aplanatic system, with little spherical aberration or coma. The array is characterized by an optical transfer function that is easily measured. An array with 19 dB crosstalk levels between adjacent antennas has been tested and it was found that the array captured 50 percent of the available power. This imaging system was diffraction limited.
Diode-pumped optical parametric oscillator
Geiger, A.R. [LaSen, Inc., Suite 600, 300 North Telshor, Las Cruces, New Mexico 88001 (United States); Hemmati, H.; Farr, W.H. [Laser Advances, Suite 5, 503 1/2 S. Myrtle Avenue, Monrovia, California 91016 (United States); Prasad, N.S. [LaSen, Inc., Suite 600, 300 North Telshor, Las Cruces, New Mexico 88001 (United States)
Diode-pumped optical parametric oscillation has been demonstrated for the first time to our knowledge in a single Nd:MgO:LiNbO{sub 3} nonlinear crystal. The crystal is pumped by a semiconductor diode laser array at 812 nm. The Nd{sup 3+} ions absorb the 812-nm radiation to generate 1084-nm laser oscillation. On internal {ital Q} switching the 1084-nm radiation pumps the LiNbO{sub 3} host crystal that is angle cut at 46.5{degree} and generates optical parametric oscillation. The oscillation threshold that is due to the 1084-nm laser pump with a pulse length of 80 ns in a 1-mm-diameter beam was measured to be {approx_equal}1 mJ and produced 0.5-mJ output at 3400-nm signal wavelength. {copyright} {ital 1996 Optical Society of America.}
Diode laser based infrared scene projector
NASA Astrophysics Data System (ADS)
Beasley, D. Brett; Cooper, John B.; Mobley, Scott B.; Buford, James A., Jr.
A high-speed dynamic IR scene projector based upon diode lasers has been designed, fabricated, and delivered to the U.S. Army Missile Command's (USAMICOM's) Research, Development, and Engineering Center (RDEC). The projector was developed under a Phase II Small Business Innovative Research award. The projector is based upon a linear array of Pb- salt diode lasers coupled with a high-speed optical scanning system, drive electronics and synchronization electronics. The projector is capable of generating high dynamic range, 128 X 128 scenes at 8 KHz frame rates. The system's modularity provides upgradability to meet specific performance requirements such as increased spatial resolution, different emission wavelengths, or dual-band scene projection. The projector's performance characteristics are presented in the paper, as well as sample images generated with the projector and captured by an InSb FPA sensor.
NSDL National Science Digital Library
Hoppe, Patrick
Created by Patrick Hoppe of the Wisconsin Online Resource Center, this primer introduces the student to the key terms and concepts associated with the silicon diode. This is a nice introductory flash presentation for those interested in this topic.
Simple Diode Rectifier Circuit
NSDL National Science Digital Library
This website from the Thayer School of Engineering at Dartmouth College features an animation of a simple diode rectifier circuit. A rectifier is an electrical device that converts alternating current (AC) to direct current (DC), a process known as rectification.
Chemically Modulated Graphene Diodes
We report the manufacture of novel graphene diode sensors (GDS), which are composed of monolayer graphene on silicon substrates, allowing exposure to liquids and gases. Parameter changes in the diode can be correlated with charge transfer from various adsorbates. The GDS allows for investigation and tuning of extrinsic doping of graphene with great reliability. The demonstrated recovery and long-term stability qualifies the GDS as a new platform for gas, environmental, and biocompatible sensors. PMID:23547771
Ming-Kwei Lee; Min-Yen Yeh; Hon-Da Huang; Chih-Wei Hong
An n-ZnSe\\/p-ZnSe\\/p+-GaAs blue light emitting diode was prepared by low pressure organometallic chemical vapor deposition. Its electroluminescence wavelength was 461 nm with a full width at half maximum 52 meV at 300 K. It shows that a pure blue ZnSe light emitting diode can be prepared under Zn-rich growth condition for n-type ZnSe epilayer doped with aluminum and under Se-rich
NASA Technical Reports Server (NTRS)
Anderson, L. M. (inventor)
Power is extracted from plasmons, photons, or other guided electromagnetic waves at infrared to midultraviolet frequencies by inelastic tunneling in metal-insulator-semiconductor-metal diodes. Inelastic tunneling produces power by absorbing plasmons to pump electrons to higher potential. Specifically, an electron from a semiconductor layer absorbs a plasmon and simultaneously tunnels across an insulator into metal layer which is at higher potential. The diode voltage determines the fraction of energy extracted from the plasmons; any excess is lost to heat.
Opel, Daniel R.; Hagstrom, Erika; Pace, Aaron K.; Sisto, Krisanne; Hirano-Ali, Stefanie A.; Desai, Shraddha
Background: In the early 1990s, the biological significance of light-emitting diodes was realized. Since this discovery, various light sources have been investigated for their cutaneous effects. Study design: A Medline search was performed on light-emitting diode lights and their therapeutic effects between 1996 and 2010. Additionally, an open-label, investigator-blinded study was performed using a yellow light-emitting diode device to treat acne, rosacea, photoaging, alopecia areata, and androgenetic alopecia. Results: The authors identified several case-based reports, small case series, and a few randomized controlled trials evaluating the use of four different wavelengths of light-emitting diodes. These devices were classified as red, blue, yellow, or infrared, and covered a wide range of clinical applications. The 21 patients the authors treated had mixed results regarding patient satisfaction and pre- and post-treatment evaluation of improvement in clinical appearance. Conclusion: Review of the literature revealed that differing wavelengths of light-emitting diode devices have many beneficial effects, including wound healing, acne treatment, sunburn prevention, phototherapy for facial rhytides, and skin rejuvenation. The authorsÆ clinical experience with a specific yellow light-emitting diode device was mixed, depending on the condition being treated, and was likely influenced by the device parameters. PMID:26155326
Application of AXUV diode detectors at ASDEX Upgrade
Bernert, M., E-mail: email@example.com; Eich, T.; Burckhart, A.; Fuchs, J. C.; Giannone, L.; Kallenbach, A.; McDermott, R. M.; Sieglin, B. [Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching (Germany)] [Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching (Germany)
In the ASDEX Upgrade tokamak, a radiation measurement for a wide spectral range, based on semiconductor detectors, with 256 lines of sight and a time resolution of 5?s was recently installed. In combination with the foil based bolometry, it is now possible to estimate the absolutely calibrated radiated power of the plasma on fast timescales. This work introduces this diagnostic based on AXUV (Absolute eXtended UltraViolet) n-on-p diodes made by International Radiation Detectors, Inc. The measurement and the degradation of the diodes in a tokamak environment is shown. Even though the AXUV diodes are developed to have a constant sensitivity for all photon energies (1 eV-8 keV), degradation leads to a photon energy dependence of the sensitivity. The foil bolometry, which is restricted to a time resolution of less than 1 kHz, offers a basis for a time dependent calibration of the diodes. The measurements of the quasi-calibrated diodes are compared with the foil bolometry and found to be accurate on the kHz time scale. Therefore, it is assumed, that the corrected values are also valid for the highest time resolution (200 kHz). With this improved diagnostic setup, the radiation induced by edge localized modes is analyzed on fast timescales.
Millimeter-wave diode-grid frequency doubler
NASA Technical Reports Server (NTRS)
Jou, Christina F.; Luhmann, Neville C., Jr.; Lam, Wayne W.; Stolt, Kjell S.; Chen, Howard Z.
Monolithic diode grids were fabricated on 2-cm square gallium-arsenide wafers in a proof-of-principle test of a quasi-optical varactor millimeter-wave frequency multiplier array concept. An equivalent circuit model based on a transmission-line analysis of plane wave illumination was applied to predict the array performance. The doubler experiments were performed under far-field illumination conditions. A second-harmonic conversion efficiency of 9.5 percent and output powers of 0.5 W were achieved at 66 GHz when the diode grid was pumped with a pulsed source at 33 GHz. This grid had 760 Schottky-barrier varactor diodes. The average series resistance was 27 ohms, the minimum capacitance was 18 fF at a reverse breakdown voltage of -3 V. The measurements indicate that the diode grid is a feasible device for generating watt-level powers at millimeter frequencies and that substantial improvement is possible by improving the diode breakdown voltage.
Fundamental mode oscillation of a buried ridge waveguide laser array
NASA Technical Reports Server (NTRS)
Mukai, S.; Katz, J.; Lindsey, C.; Kapon, E.; Rav-Noy, Z.; Margalit, S.; Yariv, A.
An eight-element phase-locked array of index-guided separate confinement ridge AlGaAs diode lasers is fabricated. In this array the absorption of light in the region between lasers is negligible and the gain profile across the array is nearly uniform. Unlike most other arrays, this array oscillates in its fundamental mode. Stable radiation patterns of near diffraction-limited single narrow beam with 1.6 deg width are obtained. The beam width approaches the theoretical limit for the present array structure.
Trumper, D.L.; Kim, W.; Williams, M.E.
Electromagnet arrays are disclosed which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness. 12 figs.
Trumper, David L. (Plaistow, NH); Kim, Won-jong (Cambridge, MA); Williams, Mark E. (Pelham, NH)
Electromagnet arrays which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness.
NSDL National Science Digital Library
Mrs. Watts
Arrays are very important in Computer Programming. An array is a way to store similar items in computer memory. The items may be numbers, words, pictures, or even sounds. Many games use an array because it is an easy way to keep track of the objects used to play the game. The Arrow Game uses an array to store arrow ...
Advances in AlGaInN laser diode technology
NASA Astrophysics Data System (ADS)
Najda, S. P.; Perlin, P.; Suski, T.; Marona, L.; Bockowski, Mike; Leszczy?ski, M.; Wisniewski, P.; Czernecki, R.; Kucharski, R.; Targowski, G.; Watson, S.; Kelly, A. E.
The latest developments in AlGaInN laser diode technology are reviewed. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., i.e, 380nm, to the visible, i.e., 530nm, by tuning the indium content of the laser GaInN quantum well. Advantages of using Plasma assisted MBE (PAMBE) compared to more conventional MOCVD epitaxy to grow AlGaInN laser structures are highlighted. Ridge waveguide laser diode structures are fabricated to achieve single mode operation with optical powers of >100mW in the 400-420nm wavelength range that are suitable for telecom applications. Visible light communications at high frequency (up to 2.5 Gbit/s) using a directly modulated 422nm Galliumnitride (GaN) blue laser diode is reported. High power operation of AlGaInN laser diodes is demonstrated with a single chip, AlGaInN laser diode `mini-array' with a common p-contact configuration at powers up to 2.5W cw at 410nm. Low defectivity and highly uniform GaN substrates allow arrays and bars of nitride lasers to be fabricated. GaN laser bars of up to 5mm with 20 emitters, mounted in a CS mount package, give optical powers up to 4W cw at ~410nm with a common contact configuration. An alternative package configuration for AlGaInN laser arrays allows for each individual laser to be individually addressable allowing complex free-space and/or fibre optic system integration within a very small form-factor.
Analysis of Photovoltaic (PV) Module during Partial Shading based on Simplified Two-Diode Model
NASA Astrophysics Data System (ADS)
Chitti Babu, B.; Gurjar, Suresh; Meher, Ashish
Generally, the characteristics of photovoltaic (PV) array are largely affected by solar temperature, solar irradiance, shading patterns, array configuration and location of shading modules. Partial shading is due to moving clouds and shadows of nearby obstacles and can cause a significant degradation in the output of PV system. Hence, the characteristics of PV array get more multifaceted with multiple peaks. The ultimate aim of the paper is to analyze the performance of PV module during such adverse condition based on simplified two-diode model. To reduce the computational time, the simplified two-diode model has a photocurrent source in parallel with two ideal diodes. Only four parameters are required to be calculated from datasheet in order to simulate the model. Moreover, the performance of PV array is evaluated at different shaded patterns and it is found that the model has less computational time and gives accurate results.
Electronic beamsteering of active arrays with phase-locked loops
R. D. Martinez; Richard C. Compton
A new electronic beamsteering technique for active arrays is presented along with experimental results at 10 GHz. The technique uses a single balanced diode mixer to phase-lock neighboring oscillators in an active array. Each oscillator has its own antenna that radiates energy into free space, so the phase difference between oscillators determines the direction of the main radiating beam. An
High frequency ultrasonic imaging using optoacoustic arrays
T. Buma; J. D. Hamilton; M. Spisar; M. O'Donnell
Optical generation and detection of ultrasound is a promising alternative to piezoelectricity for high frequency arrays. We have used the thermoelastic effect to produce high frequency, broadband ultrasound in water. A pulsed diode laser, followed by an erbium doped fiber amplifier, is focused onto a light absorbing film deposited on a transparent substrate. Conversion efficiency was improved by 18 dB
Integrated Microwave Tunnel Diode Device
H. C. Okean
A microwave tunnel diode amplifier usually requires both a stabilizing network and one or more reactive tuning elements associated with the tunnel diode. The stabilizing network insures satisfaction of the appropriate stability criteria governing the given amplifier configuration at all frequencies within the active frequency range of the tunnel diode (dc to resistive cutoff frequency) and, in particular, those outside
Light emitting diodes Enyuan Xie*
Strathclyde, University of
Light emitting diodes Enyuan Xie* Institute of Photonics, SUPA, University of Strathclyde, Glasgow based light emitting diodes *E-mail: firstname.lastname@example.com Basic principle Applications Remained problems Due to the low energy consumption and many applications, semiconductor based light emitting diodes
Soft holographic interference lithography microlens for enhanced organic light emitting diode light extraction
Joong-Mok Park; Zhengqing Gan; Wai Y. Leung; Rui Liu; Zhuo Ye; Kristen Constant; Joseph Shinar; Ruth Shinar; Kai-Ming Ho
Very uniform 2 m-pitch square microlens arrays (LAs), embossed on the blank glass side of an indium-tin-oxide (ITO)-coated 1.1 mm-thick glass, are used to enhance light extraction from organic light-emitting diodes (OLEDs) by 100%, significantly higher than enhancements reported previously. The array design and size relative to the OLED pixel size appear to be responsible for this enhancement. The arrays
Kowalsky, W.; Ammermann, D.; Boehler, A.; Dirr, S. [TU Braunschweig (Germany). Inst. fuer Hochfrequenztechnik
Light emitting diodes based on organic semiconductors (OLEDs) have attracted increased research interest over the last decade due to their potential for low cost flat panel displays. Multilayer devices allow to achieve efficient and bright light emission in the entire visible spectral region. The principle of operation is similar to that of inorganic light emitting diodes (LEDs). Holes and electrons are injected from opposite contacts through separate transport layers into the emission layer. Recombination leads to the formation of singlet excitons that decay radiatively.
Infrared diode laser spectroscopy
S. Civis; J. Cihelka; I. Matulkovß
Three types of lasers (double-heterostructure 66 K InAsSb\\/InAsSbP laser diode, room temperature, multi quantum wells with\\u000a distributed feedback (MQW with DFB) (GaInAsSb\\/AlGaAsSb based) diode laser and vertical cavity surface emitting lasers (VCSELs)\\u000a (GaSb based) have been characterized using Fourier transform emission spectroscopy and compared. The photoacoustic technique\\u000a was employed to determine the detection limit of formaldehyde (less than 1 ppmV)
Image monitoring of pharmaceutical blending processes and the determination of an end point by using a portable near-infrared imaging device based on a polychromator-type near-infrared spectrometer with a high-speed and high-resolution photo diode array detector.
Murayama, Kodai; Ishikawa, Daitaro; Genkawa, Takuma; Sugino, Hiroyuki; Komiyama, Makoto; Ozaki, Yukihiro
In the present study we have developed a new version (ND-NIRs) of a polychromator-type near-infrared (NIR) spectrometer with a high-resolution photo diode array detector, which we built before (D-NIRs). The new version has four 5 W halogen lamps compared with the three lamps for the older version. The new version also has a condenser lens with a shorter focal point length. The increase in the number of the lamps and the shortening of the focal point of the condenser lens realize high signal-to-noise ratio and high-speed NIR imaging measurement. By using the ND-NIRs we carried out the in-line monitoring of pharmaceutical blending and determined an end point of the blending process. Moreover, to determinate a more accurate end point, a NIR image of the blending sample was acquired by means of a portable NIR imaging device based on ND-NIRs. The imaging result has demonstrated that the mixing time of 8 min is enough for homogeneous mixing. In this way the present study has demonstrated that ND-NIRs and the imaging system based on a ND-NIRs hold considerable promise for process analysis. PMID:25741896
Possible dosimeter for ultraviolet radiation
A. Davis; G. H. W. Deane; B. L. DIFFEY
WHILE evaluating the weathering characteristics of the plastics polysulphone and polyphenylene oxide (PPO) we found that they both darkened when exposed to ultraviolet radiation1. We realised the potential of these polymers as monitors for ultraviolet radiation and are developing them for this use. PPO is now being used to monitor continuously solar ultraviolet radiation at forty sites throughout the world2.
SU-E-T-87: Comparison Study of Dose Reconstruction From Cylindrical Diode Array Measurements, with TLD Measurements and Treatment Planning System Calculations in Anthropomorphic Head and Neck and Lung Phantoms
Benhabib, S; Cardan, R; Huang, M; Brezovich, I; Popple, R [University of Alabama at Birmingham, Birmingham, AL (United States); Faught, A; Followill, D [UT MD Anderson Cancer Center, Houston, TX (United States)
Purpose: To assess dose calculated by the 3DVH software (Sun Nuclear Systems, Melbourne, FL) against TLD measurements and treatment planning system calculations in anthropomorphic phantoms. Methods: The IROC Houston (RPC) head and neck (HN) and lung phantoms were scanned and plans were generated using Eclipse (Varian Medical Systems, Milpitas, CA) following IROC Houston procedures. For the H and N phantom, 6 MV VMAT and 9-field dynamic MLC (DMLC) plans were created. For the lung phantom 6 MV VMAT and 15 MV 9-field dynamic MLC (DMLC) plans were created. The plans were delivered to the phantoms and to an ArcCHECK (Sun Nuclear Systems, Melbourne, FL). The head and neck phantom contained 8 TLDs located at PTV1 (4), PTV2 (2), and OAR Cord (2). The lung phantom contained 4 TLDs, 2 in the PTV, 1 in the cord, and 1 in the heart. Daily outputs were recorded before each measurement for correction. 3DVH dose reconstruction software was used to project the calculated dose to patient anatomy. Results: For the HN phantom, the maximum difference between 3DVH and TLDs was -3.4% and between 3DVH and Eclipse was 1.2%. For the lung plan the maximum difference between 3DVH and TLDs was 4.3%, except for the spinal cord for which 3DVH overestimated the TLD dose by 12%. The maximum difference between 3DVH and Eclipse was 0.3%. 3DVH agreed well with Eclipse because the dose reconstruction algorithm uses the diode measurements to perturb the dose calculated by the treatment planning system; therefore, if there is a problem in the modeling or heterogeneity correction, it will be carried through to 3DVH. Conclusion: 3DVH agreed well with Eclipse and TLD measurements. Comparison of 3DVH with film measurements is ongoing. Work supported by PHS grant CA10953 and CA81647 (NCI, DHHS)
Development of ultraviolet lasers
NASA Technical Reports Server (NTRS)
Walters, G. K.
The pulsed electron accelerator selected for use in the development of ultraviolet laser capability suitable for use in photoexcitation and photoionization studies of the upper atmosphere is reported. Performance figures, installation specifications, and total cost of the equipment are briefly shown, and plans for further studies are outlined.
Psoriasis and ultraviolet radiation
Farber, E.M.; Nall, L. (Psoriasis Research Institute, Palo Alto, CA (United States))
Prevention and detection screening programs as a public health service in curtailing the ever-increasing incidence of all forms of skin cancer are reviewed. The effect of solar and artificial ultraviolet radiation on the general population and persons with psoriasis is examined. 54 refs.
Ultraviolet reflective coating
NASA Technical Reports Server (NTRS)
Schutt, J. B.
Composition consists of dispersion of barium sulphate in aqueous solution of water-soluble inorganic binder. Binder is selected from group consisting of alkali metal sulphates. Coating exhibits high reflectance of ultraviolet light to wavelengths of approximately 200.0 nm, which compares favorably with high reflectance of virgin barium sulphate power.
The U.S. EPA operates a network of 21 Brewer spectrophotometers located at strategic points around the United States to monitor and study ultraviolet (UV) solar radiation and ozone levels. Many different types of instruments have been designed specifically for UV and ozone data ...
Line Tunable Ultraviolet Laser
NASA Technical Reports Server (NTRS)
Walsh, Brian M.; Barnes, Norman P.
An ultraviolet laser is demonstrated using a dual wavelength Nd:YAG oscillator, sum frequency and second harmonic process. Synchronous pulses at 1.052 and 1.319 micrometers are amplified, mixed and subsequently doubled, producing pulses at 0.293 micrometers.
Silicon Carbide Schottky Barrier Diode
NASA Technical Reports Server (NTRS)
Zhao, Jian H.; Sheng, Kuang; Lebron-Velilla, Ramon C.
This chapter reviews the status of SiC Schottky barrier diode development. The fundamental of Schottky barrier diodes is first provided, followed by the review of high-voltage SiC Schottky barrier diodes, junction-barrier Schottky diodes, and merged-pin-Schottky diodes. The development history is reviewed ad the key performance parameters are discussed. Applications of SiC SBDs in power electronic circuits as well as other areas such as gas sensors, microwave and UV detections are also presented, followed by discussion of remaining challenges.
Compton diode development program
Compton diodes (CD's) have been used for a number of years for ; diagnostic gamma measurements. About 1965 the demand increased for their use as ; gamma sensors to trigger oscilloscopes on nuclear tests at the Nevada Test Site. ; This report covers the steps taken in developing the Mod 3 family of low-cost ; CD's for trigger signal sensors.
B. V. Zhdanov; R. J. Knize
Diode pumped alkali lasers attract growing attention during the past several years because they have demonstrated potential to compete and, possibly, replace the best existing high power laser systems. In spite of the fact that an optically pumped alkali (potassium) vapor laser was first proposed by A.L. Schawlow and C.H. Townes in 1958, the intensive research and development of alkali
Chen, Zhen; Wong, Carlaton; Lubner, Sean; Yee, Shannon; Miller, John; Jang, Wanyoung; Hardin, Corey; Fong, Anthony; Garay, Javier E; Dames, Chris
A thermal diode is a two-terminal nonlinear device that rectifies energy carriers (for example, photons, phonons and electrons) in the thermal domain, the heat transfer analogue to the familiar electrical diode. Effective thermal rectifiers could have an impact on diverse applications ranging from heat engines to refrigeration, thermal regulation of buildings and thermal logic. However, experimental demonstrations have lagged far behind theoretical proposals. Here we present the first experimental results for a photon thermal diode. The device is based on asymmetric scattering of ballistic energy carriers by pyramidal reflectors. Recent theoretical work has predicted that this ballistic mechanism also requires a nonlinearity in order to yield asymmetric thermal transport, a requirement of all thermal diodes arising from the second Law of Thermodynamics, and realized here using an 'inelastic thermal collimator' element. Experiments confirm both effects: with pyramids and collimator the thermal rectification is 10.9 ▒ 0.8%, while without the collimator no rectification is detectable (<0.3%). PMID:25399761
Monolithic tunable diode lasers
L. A. Coldren
After over two decades of exploration, tunable diode lasers are beginning to find significant applications, driven largely by the huge demand for bandwidth that is guiding many developments in the optical fiber communication business today. In the paper, some of the history and key developments that have led to the technologies available today are reviewed from the perspective of the