text:
|Publication number
|Publication type
|Application number
|Publication date
|Aug 26, 2003
|Filing date
|Sep 14, 2001
|Priority date
|Jan 8, 2001
|Fee status
|Also published as
|Publication number
|Jayantilal S. Patel, Zhizhong Zhuang
|Original Assignee
|Optellios, Inc.
|Export Citation
|BiBTeX, EndNote, RefMan
|Patent Citations (20), Non-Patent Citations (2), Referenced by (10), Classifications (5), Legal Events (7)
|External Links: USPTO, USPTO Assignment, Espacenet
This application claims the priority of U.S. Provisional Patent Application S No. 60/260,247, filed Jan. 8, 2001.
1. Field of the Invention
The invention relates to the field of optical wavelength selection to enable optical energy to be processed selectively as a function of wavelength. In particular, the invention provides a tunable narrow band polarization encoder.
According to an inventive aspect, a Fabry-Perot element (an "etalon" comprising two reflectors spaced along a beam path) is used in a reflective mode, with the cavity between the reflectors containing a preferably-controllable birefringent material. The second reflector can be highly reflective, such that all or a high proportion of the incident light energy is reflected back along the path of the incident beam. The birefringent material imparts a polarization transformation exclusively to the resonant wavelength component (or components) of the input beam.
The resonant components have an effective optical path between the first and second reflectors of the Fabry-Perot element or etalon that is equal to, or has an integer multiple that is equal to, half the resonant wavelength. The entire input beam could be reflected by a reflective Fabry-Perot, but the polarization transformation is applied to the wavelength(s) that resonate in the cavity. The situation is such that most or all of the light is reflected, but the nonresonant component is reflected at the first reflector and the resonant component is affected by the cavity.
A birefringent material can be disposed in the cavity. A birefringent material has two refractive indices, ne and no. An incident beam that is aligned on an angle θ can be divided into orthogonal polarization components parallel to the ne and no birefringent axes. The polarization aspect adds another factor because one of the different polarization components may be resonant while the other is not.
In any event, a polarization transformation can be arranged according to the invention to produce a polarization condition that thereafter can be used as a criterion to discriminate or separate the wavelength from the remainder of the beam, for example using a polarization filter or beam splitter. This has some very useful applications.
According to a further inventive aspect, control of a birefringent element in the cavity, such as applying a control voltage to a liquid crystal birefringent element, adjusts the effective optical length of the path between the reflectors, at least for one polarization axis aligned to ne or no of the incident beam, permitting tuning for selection of the resonant wavelength that undergoes polarization transformation.
The first reflector is preferably highly reflective and the second reflector can be substantially completely reflective (e.g., over 99%), or perhaps allowing a small amount of light to pass through to a monitoring sensor. The reflectors turn a high proportion of the light energy backwards along the path of the incident beam. However the resonant wavelength of the Fabry-Perot etalon has an altered polarization orientation (rotated 90 degrees in an exemplary embodiment described below). This distinct polarization attribute marks the resonant wavelength and provides an aspect whereby it is possible further along the reflected beam path to discriminate for that wavelength.
A number of specific applications of such a reflective Fabry-Perot element are disclosed for distinct polarization marking or similarly facilitating selective processing of particular wavelengths. The elements can be employed with polarization diversity arrangements such as crystals, polarization beam splitters, half wave plates and the like, to achieve given conditions such as a predetermined reference polarization orientation in the incident beam, whereby the polarization transformation produces a detectable difference in the affected component, namely the resonant wavelength. The device can be pixilated or otherwise laterally subdivided for parallel processing of plural beams such as beams carried by separate optical fibers. The devices can be cascaded such that plural wavelengths are selected in turn, and each is distinctly polarized. These wavelengths can then be discriminated, separated or otherwise handled independently due to their distinct polarization.
An inventive Fabry-Perot element is provided with birefringent material in a cavity between at least two surfaces that are each at least partly reflective. The second reflector (or the last of a cascaded series) is preferably substantially fully reflective. The reflecting surfaces are spaced by a distance equal to one or more integral half wavelengths of a particular resonant wavelength. The action of a Fabry-Perot etalon usually is to pass light at the resonant wavelength through two spaced reflectors and to reflect other wavelengths, i.e., as a narrow bandpass filter. In the reflective mode according to the invention, the two reflective surfaces introduce a π phase shift between two reflected beams, namely one reflected from the front reflective surface and the other from the cavity. The cavity between the reflectors contains the birefringent material.
The Fabry-Perot element can be tunable. Controllable liquid crystals preferably are used in the cavity for at least part of the birefringent material. Control of such crystal by application of a control voltage alters the effective birefringence, and is used according to the invention to adjust the effective optical distance between the reflectors as applied to one of two mutually perpendicular axes of the incident beam.
In an exemplary arrangement, the input beam can be plane polarized and oriented at 45 degrees to the fast axis of the birefringent material. The selected wavelength, namely the resonant wavelength of the beam incident on the Fabry-Perot element, undergoes a polarization transformation that the remainder of the beam does not undergo. In the example, the selected wavelength undergoes a 90 degree polarization rotation for linearly polarized light at 45 degrees with respect to the fast axis of the birefringent material in the cavity. In this example, the orientation of the plane polarized input beam is such that part of the incident light energy is affected by the polarization transformation, and the adjustable birefringence of the birefringent material permits tuning for selection of the resonant wavelength. Other arrangements and orientations are possible that allow the controllable birefringence to operate on a selected wavelength of the input beam, provided that the necessary conditions are present (e.g., the resonant wavelength must be present in the input and appropriately aligned, etc.). For example, the tuning arrangement can be coupled to other tuning arrangements, such as piezoelectric tuning controls for adjusting spacing, electroclinic crystal controls for adjusting the orientation of the birefringence, etc.
A number of additional aspects will become apparent in the detailed description and the examples of specific optical processing steps and elements that appear in the detailed disclosure below.
2. Prior Art
It is sometimes advantageous to separate light at one or more wavelengths from light at other wavelengths as the plural wavelengths propagate together as a group. For this purpose, a tuned or tunable wavelength-separating device is needed. Without limitation, such tuned or tunable wavelength selective devices might be helpful, for example, to enable comparative measurement of energy at a range of wavelengths (i.e., spectral content), to filter light used for illumination or reflected from a target, for modulating or demodulating specific wavelengths in wavelength modulation or in wavelength division multiplexed optical communications, and other applications. In connection with optical fibers, a primary application of such devices is in connection with applying information signals to light and extracting the information signals thereafter (modulating and demodulating). Such mechanisms require some sort of technique or mechanism by which certain wavelengths or bands are treated differently than others.
Optical wavelength division multiplexing (WDM) can provide substantial bandwidth over a signal path, for example carrying light on an optical fiber with information bearing signals transmitted simultaneously at several different wavelengths over the same optical fiber. Wavelength selective elements are used or are advantageous for purposes such as selecting a wavelength band to be modulated (by amplitude or wavelength), from a broad band or other multiple wavelength signal, or selecting a band to be demodulated, or actually modulating and/or demodulating at the selected wavelength or within a bandwidth around a center wavelength.
There are a number of potential methods for separating light at multiple wavelengths into discrete beams of the constituent wavelengths. Wavelength-dependent separating devices can range, for example, from simple refractive prisms to complex spectrometers with diffraction gratings. Such devices can cause a beam to diverge as constituent wavelengths directed at different angles, whereby the constituent wavelengths can be discriminated, directed or sensed. Other devices also are known, such as waveguide demultiplexers and multiplexers and acousto-optic devices.
Fabry-Perot devices are a known form of transmissive filter that passes only a specific wavelength determined by the resonant distance between two reflectors, and blocks other wavelengths, typically reflecting the blocked wavelengths back in the opposite direction from incident beam. Between the two spaced reflectors of a Fabry-Perot device, the light energy is reflected back and forth between the reflectors. The light energy interferes and at specific wavelengths produces a standing wave. Where the space between reflectors is equal to the length of a standing wave (precisely one half wavelength, or precisely an integral number of half wavelengths), incident light directed normal to spaced parallel reflector planes can pass through the two spaced reflectors. All other wavelengths are effectively blocked.
Therefore, a parallel spaced reflector pair or "Fabry-Perot" element or etalon may be useful as a filter to pass only a predetermined set of wavelengths. The Fabry-Perot structure, and in particular the reflector spacing, may be chosen to support resonance at plural wavelengths that are present, or the structure can be chosen to eliminate higher order modes. In a real world device, a Fabry-Perot passes a limited passband. The bandwidth is determined by dimensional variations of the cavity between the reflectors and by reflectivity. The narrowness or broadness of the passband is associated with a characterizing factor known as "finesse."
A Fabry-Perot element could consist of a static pair of reflectors rigidly spaced by an air gap, thus passing a fixed wavelength (or assuming integer multiples, a fixed set of wavelengths). A Fabry-Perot may be arranged to filter for a selected tunable wavelength by providing a means to change the effective optical cavity length between the reflectors in one way or another. The cavity length might be changed by moving either or both of the parallel reflectors toward or away from one another. Alternatively, the physical spacing between the reflectors could be unvarying, but the index of the material in the cavity might be changeable. For example, it is known to use controllable liquid crystals in a cavity of a light transmissive Fabry-Perot, and to select the wavelength that is transmitted by changing the index of the liquid crystal in the cavity.
Known Fabry-Perot devices necessarily are transmissive rather than reflective. There is no reason to select a particular wavelength if that selected wavelength is immediately recombined with the wavelengths that were not selected. Such recombination occurs inherently if the Fabry-Perot is reflective rather than transmissive. The point of Fabry-Perot devices is to separate a selected bandpass wavelength from other wavelengths and to allow only the selected wavelength to pass. The passed wavelength(s) is (are) directed along an optical path that is different from the paths of other wavelengths that are not selected. If one considers a reflective device of this type, the effect would be to direct the selected wavelength along the same optical path as the non-selected remaining wavelengths, thus making no change in polarization properties. Any benefit associated with selecting a particular wavelength would be lost when the selected and unselected portions were recombined.
A Fabry-Perot element is resonant at a particular wavelength because its reflectors are spaced to correspond to that wavelength (actually one half-wavelength) and a standing wave is produced between the reflectors. Wavelengths other than the resonant wavelength are reflected but the resonant wavelength is passed or transmitted through the element or etalon. The element is a narrow passband filter that passes only its resonant wavelength. An example of a Fabry-Perot etalon having this narrow bandpass characteristic is disclosed, for example, in U.S. Pat. No. 5,321,539—Hirabayashi et al. That patent also discloses using a liquid crystal material in the cavity between the Fabry-Perot etalon reflectors. A liquid crystal material can be oriented along a so-called buffing or rubbing axis and controlled anisotropically, by application of an electric field. The liquid crystal defines a different optical path length along mutually perpendicular axes for mutually perpendicular polarization components of an incident beam. In this manner, polarized light aligned at the required orientation, or at least having a vector component at the required orientation, can be caused to traverse an optical path having a length that can be modified by an electrical signal. With reference to the Fabry-Perot etalon, the resonant wavelength is changeable along that path and thus the resonant wavelength can be electrically selected. The device can be tuned.
This aspect of a Fabry-Perot element is useful in a bandpass application to pass only the selectively tuned resonant wavelength desired. Whether or not tuned, for the reasons discussed above, there is no apparent use for such a characteristic in a reflective device rather than a transmissive one. Whether or not tuned, the selected resonant wavelength would be recombined with the non-selected wavelengths in a reflective device. Whether tuned or not, any benefit associated with the selection or discrimination is lost because the wavelengths are recombined.
Various devices have been produced to take advantage of the selective nature of a Fabry-Perot element in a forward or transmissive direction. Examples include, for example, U.S. Pat. Nos. 5,068,749, 5,111,321 and 5,150,236, all to Patel; and 5,452,127—Wagner, the disclosures of which are hereby incorporated.
It is an aspect of the present invention that one or more wavelengths of a beam are marked selectively. Although the marked and unmarked wavelengths may be recombined, the marking is useful as a characteristic to select for the presence of that wavelength or to divert that wavelength, using a beam splitter, prism, grating or the like.
Examples of efforts in the areas of combining and separating wavelengths include U.S. Pat. Nos. 6,154,591—Kershaw, 6,208,444—Strong et al. and 6,222,958—Paiam. In another example, in U.S. Pat. No. 6,125,220—Copner et al., transmitted and reflected beams exiting a partly reflective etalon are processed and recombined.
What is missing in the prior art is a simple and effective way to exploit the resonant cavity aspects of a Fabry-Perot or another similar resonant optical cavity device (such as a ring resonator) in a wholly reflective way. The prior art lacks an effective way to apply an incident beam to an optical element that marks one or more preferably-tunably-selected resonant wavelengths in a way that permits those specific wavelengths to be discriminated, and returns the whole incident beam, including those wavelengths (now distinctively marked) and the other wavelengths as well.
It is an object of the invention to provide a polarization-based method and apparatus wherein an optical interferometer contains a birefringent material for producing a wavelength-dependent polarization transformation.
It is an object of the present invention to provide a polarization-based mechanism in association with a Fabry-Perot or similar resonant optical structure employed in a reflective mode, with a polarization transformation provides a distinctive marking aspect whereby the resonant wavelength can be separated from the remainder of the reflected light, to provide useful devices. This mechanism, preferably comprising a Fabry-Perot structure containing controllable birefringent material for tuning, produces selective narrow band polarization that is useful as an encoding device and can be used as a tunable wavelength selective device and in other ways that are discussed in this disclosure.
The invention is a tunable narrow band polarization encoder that introduces a π phase shift between two orthogonal states of polarization of a selected narrow band in an input beam. Effectively the invention behaves like a narrow band tunable half wave plate.
In some more particular arrangements, the invention is selective by virtue of the input beam orientation. In some of the disclosed examples, the input beam is plane polarized and a wavelength selective arrangement alters the differential phase between the components corresponding to the two orthogonal birefringence axes, which results in a polarization transformation of that wavelength.
The invention is applicable to a general case in which a single wavelength of a plane polarized input beam is marked by polarization transformation and diverted by a polarization sensitive beam splitter. A number of other arrangements are also disclosed, including for example arrangements to ensure a particular input beam polarization orientation or to process the polarization transformed output. In one example the Fabry-Perots or optical resonance elements are cascaded whereby plural selected and preferably-tuned wavelengths are marked with polarization transformations permitting the marked components to be discriminated.
These and other objects are met according to the invention in a Fabry-Perot optical resonance cavity that is operated in a fully reflective mode and is provided with a birefringent material in a cavity between two reflectors. A first mirror, for example of about 90% reflectance and a second mirror, for example of 99% reflectance, define the cavity. A polarization transformation is applied exclusively to a resonant wavelength that is defined by the spacing of the two reflectors and by the orientation of the birefringent medium, which is preferably tunably controllable. Preferably, the entire input beam is reflected back in the direction of incidence. However the resonant wavelength component therein has experienced a polarization transformation whereby the resonant wavelength differs from the non-resonant wavelengths. This difference permits discrimination for the resonant wavelength, for example, for selective diversion using a polarization beam splitter. A number of applications are disclosed, including using a birefringent liquid crystal and tuning the apparent optical path length by electrically adjusting the birefringence. The device also is cascadable for selectively operating on certain wavelengths and diversely polarizing some wavelengths and not others. In one embodiment wherein the purpose is to separate the resonant wavelength, the input beam can be applied at 45 degrees to the slow axis of buff-oriented birefringent nematic liquid crystal. Additional variations also are possible.
The drawings illustrate certain embodiments of the invention as presently preferred. It should be understood that the invention is subject to certain variations from the illustrated embodiments, which are nevertheless in keeping with the invention encompassed by the appended claims, particularly insofar as the concepts taught in this disclosure are applied to practical devices. In the drawing figures,
FIG. 1 is a schematic illustration of a conventional Fabry-Perot transmissive device, which passes a particular resonant wavelength from an incident signal including the resonant wavelength and one or more non-resonant wavelengths, the latter being blocked and reflected back in the direction of incidence.
FIG. 2 is a schematic illustration according to an inventive aspect, wherein a Fabry-Perot device is provided with a birefringent material in the cavity between the reflectors and is operated in a reflective mode. The Fabry-Perot device in this embodiment operates to change the polarization of the resonant wavelengths or passband. The polarization-transformed reflected passband is combined with the remainder of the incident beam, which is reflected without polarization transformation, at the surface of the Fabry-Perot.
FIG. 3 is a schematic illustration corresponding to FIG. 2, and illustrates operation for incident light that is polarized differently for different wavelengths, and wherein the polarization angle of a component ωd is altered by the Fabry-Perot element or etalon.
FIG. 4 is a schematic illustration further comprising a polarization beam splitter and illustrates an example of how the invention can be applied to selective separation of a given wavelength.
FIG. 5 is a schematic illustration of the invention according to FIG. 4, operating simultaneously on an X-Y array of laterally spaced beams that are subdivided in the manner of discrete pixel areas.
FIG. 6 is a schematic illustration of an application of the invention to encoding a selected wavelength and including a beam displacing crystal.
FIG. 7 is a schematic illustration of a stacked configuration for a packaged device according to the invention, including a polarization independent reflective encoder and phase plates coupled to optical fibers.
FIGS. 8a and 8 b separately illustrate the forward and reflected paths of a beam in a polarization diversity structure for a reflective Fabry-Perot according to the invention with polarization-wavelength encoding.
FIG. 9 is a schematic illustration of an opto-electronic package corresponding to the exploded view of FIGS. 8a, 8 b.
FIG. 10 illustrates a polarization independent reflective encoder using beam splitters and phase plates.
FIG. 11 illustrates an embodiment that is functionally similar to FIG. 10 but has a different geometry.
FIGS. 12a and 12 b illustrate two embodiments having cascaded reflective Fabry-Perots for serial or sequential selection of selected wavelengths tuned or controlled by the cascaded Fabry-Perot elements individually.
FIG. 13a and 13 b illustrate functional an physical aspects of a cascaded wavelength selective device that is controllable for selective routing of wavelengths to either of two output ports.
FIGS. 14 through 16 are graphic illustrations of reflective spectra of a Fabry-Perot according to the invention, demonstrating tunability and other aspects that are discussed below.
FIG. 17 is a graphic illustration of the user interface of a simulator program developed to demonstrate the invention, representative outputs being shown also in FIG. 18.
FIGS. 19a, 19 b and 20 a, 20 b compare simulator presentations and spectral measurement data respectively showing the area of convergence of the resonant wavelengths at controlled and static axes of a liquid crystal controllable birefringent material.
FIGS. 21a, 21 b show comparable simulator and spectral measurement data for operation as notch filter.
FIGS. 22 and 23 show simulator outputs for several examples of cascaded arrangements as discussed below.
The invention is based upon and exploits the discovery that an optical resonant chamber such as a Fabry-Perot element is useful a reflective mode provided that a birefringent structure is arranged to affect the resonant wavelength only. In particular, a birefringent material is provided in the cavity of a Fabry-Perot to impart a distinct polarization transformation to the resonant wavelength. The resulting polarization attribute can later be used to discriminate for the resonant wavelength in one way or another.
Referring to FIG. 1, labeled "prior art," a Fabry-Perot element 30 conventionally comprises two parallel reflectors 32, 34, that are separated by a gap 36. The distance d across the gap 36, in a direction parallel to the beam path 38 of an incident light beam 40, which is normal to the plane of each reflector 32, 34, corresponds to an integral multiple of half-periods of a resonant wavelength ωd (which integral multiple can be one or unity or some other integer).
In FIG. 1, the incident light beam 40 and the transmitted and reflected light beams that result by operation of the Fabry-Perot 30, are shown graphically in spectral diagrams of amplitude ∀ as a function of wavelength ω. The Fabry-Perot reflectors, 32, 34 in the known transmissive Fabry-Perot structure have respective reflectivities, % R1 and % R2, such that most of the light energy is reflected back in the direction of incidence. However, the reflectors 32, 34 of the known transmissive Fabry-Perot form a resonant structure. At a particular wavelength (or a number of wavelengths, considering integer multiples), the spacing d of gap 36 is such that a standing wave is produced in the cavity between the reflectors. By virtue of positive interference and this standing wave, light at this resonant wavelength is transmitted through the two reflectors, whereas the remainder of the light incident on the device is reflected back along the direction of the incident beam. The incident beam contains the resonant wavelength ωd. Only that wavelength ωd passes or is transmitted through the known transmissive Fabry-Perot 30.
The present invention is illustrated in one embodiment in FIG. 2. The same reference numbers are used in FIG. 2 and throughout the drawings to identify comparable structures.
According to the invention as shown in FIG. 2, a Fabry-Perot is substantially reflective instead of transmissive. The front reflector 32 is a partial reflector, for example with a reflectivity of over 90% but not total reflectivity. The rear reflector 34 can be a substantially full 100% reflector, e.g., a gold coating with 99.9% reflectivity, or could have a lower reflectivity for some applications, for example to permit a monitor sensor or the like along a transmissive path to receive light energy passing through both reflectors. Thus the Fabry-Perot resonant element 30 operates substantially or exclusively in a reflective mode and not a transmissive one.
According to an inventive aspect, the gap between reflectors 32, 34 in the inventive device of FIG. 2, is occupied by a birefringent material 44, such as a liquid crystal. The resonant wavelength(s) are subjected to a polarization transformation. The remaining wavelengths are simply reflected and their polarization conditions are not altered. This amounts to altering a polarization attribute of the resonant wavelength, namely inducing a detectable differential phase condition.
In this description, liquid crystals are used as examples of the birefringent material 44 contained in the Fabry-Perot cavity 36. An advantage of liquid crystal as a birefringent material is that the birefringence is controllable by application of an electric signal, of modest voltage. By electrically adjusting the extent of birefringence, the optical path length through the crystal is adjusted along one of two mutually perpendicular axes (generally termed ne and no). The discussion of liquid crystals as an exemplary or preferred birefringent material is not meant to exclude the possibility of other birefringent materials, whether the birefringence is controllable or preset.
In general, the inventive reflective Fabry-Perot device behaves as a tunable half-wave plate operable at a resonant frequency or wavelength defined by the length of the optical path according to the tunable birefringent axis, which alters the polarization of the resonant frequency of the incident light beam and returns the entire light beam in the opposite direction from the direction of incidence. The can be appreciated with an understanding of the physical and optical properties that could conceivably vary.
One can consider a generalized Fabry-Perot element having front and rear reflectors (mirrors) that are both at least substantially reflective and preferably at least the rear one is highly reflective. The reflectors are planar, parallel, normal to and spaced along the optical axis of an incident beam. According to the invention the reflectors have a birefringent medium in the gap between them.
The incident beam and the birefringent material can be referenced to a rotational position in the normal plane, for considering their polarization aspects or effects. The birefringent material can be considered to be aligned to an optical reference or axis of angle θ. The polarization state of the incident beam may vary relative to this reference angle θ.
The medium in the gap between the reflectors is birefringent. That is to say that there are two refractive indices: ne and no. Unless the incident light happens to be plane polarized exclusively at one of the two orthogonal axes corresponding to the distinct birefringence axes having indices ne and no, the incident beam can be divided into two orthogonal components, having polarization states parallel to the axes for refractive indices ne and no, respectively. We will assume for the moment that the incident beam at issue has components at both polarization states, such that all wavelengths in the incident beam have some portion corresponding to each of the orthogonal components. We can also assume that all wavelengths are present over a bandwidth of interest. It will become apparent in the discussion that follows below, that there are useful situations where the polarization states and/or the population of incident bandwidths are special cases, but for initially we can assume that all such components, states and bandwidths are represented.
If one of the two polarization components satisfies the resonant condition regarding the length of the optical path between the reflectors, but the other polarization component does not, then the non-resonant part of the light is reflected from the front mirror and the resonant part of light is resonant inside the cavity and accumulates an additional π phase. However, whether or not the resonant condition is met depends in part on whether the refractive index is ne or no. This shows that the question of resonance in the Fabry-Perot cavity is not only a question of wavelength, but also is a question of polarization state and/or orientation.
Because of the π phase difference between the two orthogonal components of the light for the resonant wavelength, the device behaves like a waveplate oriented at angle θ. The retardation of the waveplate is half-wave (i.e., π) for the resonant wavelength.
The reflective Fabry-Perot behaves like a waveplate only for the wavelengths that are on or close to resonance. For other wavelengths, the reflective Fabry-Perot behaves just like an ordinary mirror.
For the wavelength that is "exactly" on resonance, the phase retardation is half-wave (π), which is the theoretical ideal case. There is also a bandwidth aspect to be considered, and the device operates to an extent on wavelengths that are close to the exact resonant wavelength. For wavelengths that vary slightly from resonance, the magnitude of the phase retardation varies as a function of the extent of difference in wavelength between the respective wavelength under consideration, and the resonant wavelength. In other words, for wavelengths that are very far from resonance, the phase retardation is zero. The phase retardation approaches π as the wavelength approaches the resonance wavelength. The spectral bandwidth of non-zero retardation around phase retardation of π at the resonant center wavelength, is dependent on the attribute of the Fabry-Perot element known as "finesse."
Applying the foregoing for the special case where the incident light is linearly polarized at an angle φ, the state of polarization of the resonant wavelength will remain linear but rotated by 2(θ-φ).
For the special case, when θ=45� and the incident light is linearly polarized at 0� or 90�, the state of polarization will be rotated by 90� with respect to the state of polarization of the off-resonant wavelength. This provides a means to completely separate the resonant and off-resonant wavelength.
As shown in FIG. 2 and in the schematic representation of FIG. 3 (which shows the polarization transformation of the resonant wavelength ωd), an incident beam 40 is applied to the inventive device 30. The component wavelengths of this incident beam may be randomly polarized or plane polarized at one or more angles oriented on both sides of a fast axis 48. For purposes of illustration, the incident beam 40 in the example of FIG. 3 includes vertical and horizontal plane polarized light of various wavelengths, and the birefringence fast axis is at 45 degrees. As a result, the vertical and horizontal plane polarized light will include a vector component corresponding to each birefringence axis ne and no. The incident beam 40 in the example shown could be randomly polarized or plane polarized but has at least a component portion that corresponds to the controllable birefringence axis of the birefringent material 44. The incident beam also has a component portion at the resonant wavelength to which the Fabry-Perot is to be tuned. These conditions enable the Fabry-Perot to produce useful effects.
Assuming, for example, that the incident beam 40 is plane polarized, it could have a vertical or horizontal orientation and would correspond with a birefringent material in which the controlled and uncontrolled axes are oriented orthogonally. According to an inventive aspect, the fast axis 48 of the birefringent material 44 is oriented at 45 degrees, which is intended to illustrate that some of the incident light is polarized in each of the perpendicular axes such that the polarization transformation produces a detectable change. The input polarization does not have to be limited to a given orientation or the same for all wavelengths.
The specific resonant wavelength ωd that traverses the resonant Fabry-Perot cavity 36, is operated upon by the birefringent material 44 in the cavity. The non-resonant wavelengths are reflected initially and are not affected by the birefringent cavity material 44, which only operates on the resonant wavelength ωd.
One of the incident wavelengths, in particular a narrow passband ωd, is resonant, which is a characteristic of Fabry-Perot devices. The front and rear reflectors 32, 34 are spaced by an integral number of half wavelengths (one or more), such that the cavity 36 between the reflectors 32, 34 can resonate at those wavelengths with a standing wave. Conventionally, the resonant wavelength would be admitted and would pass through the two reflectors (FIG. 1), the non-resonant wavelengths being reflected at the first-encountered reflector. According to the invention (FIGS. 2 and 3), the Fabry-Perot element 30 is arranged to operate reflectively and the resonant wavelength ωd is reflected back through the cavity and produces a reflected beam opposite to the direction of incidence.
In the embodiment shown, the rear mirror 34 according to the invention is substantially completely reflective. In general, the rear mirror is substantially reflective so as to ensure that substantial light energy is reflected back without introducing losses. However, the rear mirror need not be 100% reflective for the reflective aspects discussed herein to work effectively. Moreover, if the reflectivity of the rear mirror is large but less than 100%, a small amount of light can be allowed to pass for useful purposes. For example, a small proportion of the light could be allowed to pass for impinging on a detector placed after the rear mirror 34 along the beam path. Such a detector could have distinct advantages, for example for monitoring purposes, for developing an input signal to be used for feedback control or for other similar uses.
As shown in FIGS. 2 and 3, the incident and the reflected beams both contain all the wavelengths, including the resonant wavelength ωd, which might seem to defeat any benefit to the device. However, an inventive aspect is that the cavity of the reflective Fabry-Perot element is birefringent. The resonant wavelength or bandwidth ωd undergoes 90-degree polarization rotation in the reflected beam, whereas the remainder of the wavelengths do not. This difference marks the resonant wavelength ωd in a way that has useful applications, discussed in detail below. The birefringent material provides a distinct and detectable aspect to the resonant wavelength that is useful for encoding and decoding in that it provides a controllable marker for a selective wavelength of the incident/reflected light.
In the configuration shown in FIG. 2, the resonant wavelength ωd undergoes a polarization rotation with respect to the orientation of the input polarization of that wavelength, provided there is some overlap of the fast axis 48. Inasmuch as the Fabry-Perot operates such that non-resonant wavelengths are substantially reflected at the leading surface, the change in polarization orientation applies only to the resonant wavelengths. The input polarization does not have to be the same for all wavelengths but could be at least one of the two orientations, shown in FIG. 3 as vertical and horizontal lines beneath the wavelength-representing arrows in the incident and reflected beams. For example, if the input polarization is linear and oriented at 45 degrees relative to the birefringent axis, then the polarization of the resonant wavelength will be rotated by 90 degrees.
In addition to encoding wavelengths with different polarizations, the invention is useful in that the polarization change can encode information. That information is decodable as well. For example, it is possible to provide a polarization sensitive wavelength separating device as shown in FIG. 4, wherein structures such as those shown in FIGS. 2 and 3 are used in combination with appropriate polarization separating devices such as polarization beam splitters or polarization beam displacers. As an alternative, a polarization encoder device of this type can function as a polarization decoder device.
In FIG. 4, the input beam 40 is unpolarized (i.e., randomly polarized or otherwise having mutually perpendicular polarization components). This input beam 40 is separated by a polarization beam splitter 50, which separates the input beam 40 by diverting a component having one polarization orientation (e.g., horizontal) and passing to the Fabry-Perot 30 the component having the perpendicular orientation (vertical in this example). Thus all the wavelengths incident on the Fabry-Perot have the same polarization orientation. By action of the birefringent material in the cavity of the Fabry-Perot, the polarization orientation of the resonant wavelength ωd is rotated.
The Fabry-Perot element behaves like a tunable half wave plate. That is, for the resonant wavelength ωd the Fabry-Perot behaves like a half wave plate and for the non-resonant wavelengths the Fabry-Perot has no effect. The polarization beam splitter 50 diverts the resonant wavelength ωd due to its polarization orientation and passes the remainder of the reflected beam, from which the resonant wavelength ωd is wholly absent. Similar structures can be designed using other types of polarization separating devices. An example of another such structure is a calcite crystal. Furthermore, the resonant wavelength can be tuned using an electrically controllable device for the birefringent material between the reflectors on the surfaces of the Fabry-Perot element, such as a liquid crystal.
Typically, the cross sectional size of the incident light beam 40 on the device is smaller than the available size of the device. The beam cross section can be much smaller than the available area, if desired, which makes it possible to provide arrays of devices or arrays of beams that are similarly processed by one device as in FIG. 5. In the example shown in FIG. 5, an array 62 of input beams is provided in the form of parallel spaced incident beams along a line or an X-Y pattern. In such an embodiment, the incident beams of the array 62 can differ as to their content and can be processed in the same manner by the Fabry-Perot element 30 to produce an array of output beams 63, the operation being substantially the same as with one beam in FIG. 4.
In cases where there are plural beams and spaced plural points of incidence, however, the Fabry-Perot device 30 also can be subdivided and can comprise a corresponding array of independently tunable birefringent elements in a pixilated array 64. The birefringence (and the resulting optical path length) of the pixilated elements in the array can be determined by an electrical signal applied to each pixel of the array separately. This can be done in a one or two dimensional array, a two dimensional array being shown in FIG. 5.
Where plural points of incidence are provided, it is also possible to design the individual devices of the array to have different physical properties of a type that are fixed rather than tuned. For example, the individual subdivided paths where the beams are incident (which may be called pixels of the array) can have different mirror reflectivities. They can have distinct controllable or fixed gaps between the reflectors, which affects tuning or at least determines the basic path length obtained in the absence of electrical excitation. In some applications it may be desirable to have a variation of properties in one device. In that case, the discrete segmentation might be replaced by a continuous gradient of these and similar properties.
The structures shown in FIGS. 4 and 5 are sensitive to the polarization of the incident beam(s). In many applications, especially including fiber optic applications, polarization dependence may be undesirable. A polarization insensitive structure is preferable. According to an inventive aspect, the apparatus and method of the present invention can provide a polarization insensitive wavelength dependent device, using a polarization diversity arrangement. A number of different configurations are possible, which will become apparent to those skilled in the art in view of the following exemplary devices, which particularly employ calcite beam displacers and polarizing beam splitters. For simplicity, the examples are discussed with reference to single input beams, but should be understood that the invention is also applicable to multiple beam arrays. The general idea is to filter or separate components by polarization, transform one to correspond to the other, and recombine the polarization components so that an original input beam with diverse polarization conditions is replaced by a modified input beam having a known polarization orientation relative to the Fabry-Perot.
FIG. 6 illustrates an embodiment using two sets of beam displacement crystals such as calcite. A structure as shown provides a polarization insensitive device in which the selected wavelength (the resonant wavelength) is deflected to the output port, while the unselected wavelength gets reflected back into the input port. The reflected light can be tapped out by using a circulator at the input end. Alternatively, the unselected wavelengths that are reflected may be diverted into another port or otherwise handled. FIG. 7 shows the device that appears in exploded view in FIG. 6, as it might appear as a packaged element in an optical signal processing apparatus. In particular, the respective elements of the device are mounted directly to one another and electrical control leads are conveniently oriented for mounting on a printed circuit card, etc.
In the example of FIGS. 8a and 8 b, which respectively show the paths of the input and reflected beams, the unselected wavelengths are rejected by slightly tilting the reflective Fabry-Perot element 30 such that the incident and reflected beams do not directly overlap. A tilt for this purpose can be in the direction shown, orthogonal direction to that shown or at some other angle that has the effect of directing the selected wavelength along a particular path and the unselected wavelength along a different path.
FIG. 9 shows the configuration or layout used in FIGS. 8a, 8 b, in a stacked form characteristic of a packaged device or element, for example to be employed in an optical communication system, as FIG. 7 shows a packaged configuration corresponding to FIG. 6. These figures also illustrate application of the invention to subdivided or pixilated beams of light, such as incident beams from discrete fiber collimators that are arranged to impinge on discrete controllable crystal device segments provided for the individual pixels. Thus, a simple four pixel device of appropriate size would allow simple stacked structures as shown in the FIGS. 7 and 9. In FIG. 9, a pixilated half wave plate is used adjacent to a single beam displacement crystal (e.g., calcite). This is but an example, and it should be apparent that the same result could be obtained by other functionally similar arrangements. As another example, two or more adjacent crystals could be used instead of a pixilated half wave plate and one crystal, effectively achieving a similar result.
FIG. 10 shows an example of a functionally similar but geometrically different structure using polarizing beam splitters. FIG. 10 is one example of how to make a tunable polarization insensitive device which is functionally similar to the device shown in FIG. 6, namely in which the unselected wavelengths get reflected back to the input port. By tilting the reflective Fabry-Perot, it is possible to collect all reflected light into different ports, similar to the one shown in FIG. 8. The operation of the device in FIG. 10 is similar to the foregoing devices, except that the light is collected and recombined using certain passes through the polarization beam splitter 50, a prism with internal reflectors 76 and two q-wave plates 78. The results are equivalent in that the selected wavelength ωd is routed to an output port that is physically separated from the input port, and the wavelengths apart from ωd are reflected back along the input path.
An alternative functionally similar embodiment is shown in FIG. 11. This embodiment is characterized by a reduced polarization dependent path difference. FIGS. 10 and 11 essentially show that the selected wavelength ωd, through polarization encoding is discriminated and directed to an output port. By making the quarter-wave plate tunable between zero birefringence (or an integer multiple of 2π) and effective quarter-wave retardation, the output can be is switched. In effect, the device is thus switched controllably between operation as a wavelength band pass filter and operation as a notch filter, passing either the selected band on the one hand, or all but the selected band on the other hand. In this way the invention can operate as a bandpass or notch filter. The discussion of simulation results below also provided for certain intermediate effects between a notch filter and band pass filter, which can be accomplished by changing the value of the retardation plate. Additionally, it is possible to produce polarization rotation at the output by incorporating additional wave plates in the path.
A Fabry-Perot device generally is limited to selecting one wavelength at a time, or at most a series of wavelengths that are related, such as wavelengths that when added in integer multiples of one or more are equal to the distance between the Fabry-Perot reflectors 32, 34. The specific wavelength ωd may be tunable, using an electric signal to vary the optical path on one axis of birefringence, but the device at least on that axis, can only be tuned to one wavelength ωd at a time. This limitation can be overcome as demonstrated by FIGS. 12a and 12 b, wherein a plurality of independently tunable Fabry-Perots are coupled successively in cascade. According to another inventive aspect as thereby shown, multiple wavelengths propagating along the same path can be selected and selectively processed (polarized, diverted, etc.) by using more than one reflective Fabry-Perot structure according to the invention, tuned to the same or different values of ωd (i.e., ωd1, ωd2, ωd3, etc.).
In the examples shown in FIGS. 12a and 12 b, the independently tunable Fabry-Perots 30 are encountered on opposite faces along a zigzag reflective path. Each Fabry-Perot alters the polarization of a single wavelength to which it is tuned. The multiple wavelengths are separated in FIG. 12a at the end of the illustrated section of beam path, using a polarization decoder such as a beam splitter 50. The device can be polarization sensitive or can be made polarization insensitive by using diversity schemes such as those discussed above. In FIG. 12b the output simply contains a plurality of wavelengths wherein some are marked by distinct polarization.
In the examples shown in FIGS. 12a, 12 b, the angle of incidence/reflection is not exactly normal to the plane of the Fabry-Perot. The angle of incidence of the beam onto the reflectors of the reflective Fabry-Perot shown in FIG. 12 has been exaggerated for illustration purposes. The actual angle preferably is kept very small to avoid problems such as beam walk-off. It is possible to arrange the optical layout to make the angle of incidence onto the Fabry-Perot almost normal. In FIG. 12b, refraction is used to adjust the angle of incidence/reflection more nearly toward normal.
The embodiments of FIGS. 12a and 12 b are advantageous in that it is made possible to make a one by two wavelength router in which selected wavelengths from the incident beam can be routed controllably to either of two output ports. This is accomplished by selectively activating the Fabry-Perot element or elements corresponding to one or more particular desired wavelengths to be routed by polarization encoding. The polarization encoding is accomplished by electrically activating the birefringent material (e.g., liquid crystal) of the Fabry-Perot for a given wavelength, thereby modifying the polarization of that wavelength without disturbing the other wavelengths.
Any number of successive Fabry-Perots is possible as the beam passes back and forth, and each is tunable. An exemplary packaged device 80 of this type could be arranged as shown in FIGS. 13a, 13 b. FIG. 13a shows the beam path and output stage. FIG. 13b shows the external package including the electrical leads provided for selecting the resonant wavelength of the separately tunable elements.
The polarization decoder or separator 50 at the end of the path (such as a Wollaston Prism or polarization beam splitter) selectively routes the wavelengths onto one path or another depending on their polarization. The polarization of each respective wavelength for which a Fabry-Perot element 30 is tuned is thereby selectively set, and later used for discriminating, routing, encoding/decoding or similarly handling the beam is a manner specific to the respective wavelengths. This has various uses for encoding information, addressing, etc. Yet the device can be compact and functional for plural wavelengths, each of which encodes separately encodes a datum by virtue of its polarization. According to the invention, this is accomplished by making Fabry-Perot elements in the form of arrays, patterning electrodes for the arrays such that the electric fields applied to each element controls the effective birefringence of the element, and employing the device to alter the polarization of selected wavelengths to encode and decode particular wavelengths with whatever information may be desirable.
Up to this point, the discussion and examples have focused on illustrative physical examples of devices and optical layouts that are useful as applications for operating a Fabry-Perot in a reflective mode together with elements that selectively operate on either the selected (resonant) or unselected wavelengths, such as a birefringent element between the Fabry-Perot reflectors that operates on the resonant wavelength only. These examples are intended as exemplary and nonlimiting. Other specific structures are possible and will now be apparent to those skilled in the art in view of this explanation and the illustrated examples.
It is an aspect of the invention that the polarization change employed to mark selected wavelengths can be selectively applied by tuning the applicable Fabry-Perot to a given wavelength. At least a portion of the Fabry-Perot cavity contains birefringent material and the birefringent material can be controllable, either to turn the effect on and off or to alter the wavelength that is affected. The encoding and decoding are preferably controllable (i.e., activated and deactivated at different times). An advantageous controllable birefringent material for this purpose is liquid crystal, and in particular nematic liquid crystal. Other materials also are possible.
A simple nematic liquid crystal cell can comprise two glass plates that are separated by a small gap and may be coated with a conductive material that can be coupled to a voltage signal source to apply an electric field to an alignment layer. Application of the electric field serves to align the liquid crystal molecules in a desired direction. The gap between the electrodes (e.g., conductively coated glass plates) can be filled with liquid crystal and then sealed to form a liquid crystal cell as is well known in the art.
A liquid crystal Fabry-Perot 30 has a similar structure a liquid crystal cell as described, except that the Fabry-Perot has two spaced reflectors 32, 34, located on opposite sides of the liquid crystal material. For providing the reflectors, the inner surfaces of the glass plates of a liquid crystal cell structure may be coated with appropriate optically reflective coatings (i.e., mirror or at least partly silvered coatings). The mirror coatings and the resonant space between them form the Fabry-Perot cavity. The liquid crystal in the cavity is birefringent under control of a signal applied to the liquid crystal electrodes.
In a birefringent material, the refractive indices along two orthogonal directions are often different. These materials may be anisotropic. When they are confined in a Fabry-Perot cavity, they effectively give rise to two resonances, generally at different wavelengths but potentially tunable to cross or coincide at the same wavelength.
It is known that asymmetric Fabry-Perot structures can be used to produce a phase shift. In particular, considering an idealized structure in which one of the mirrors is a perfect reflector while the other has a reflectivity of R, all the light falling on this structure gets reflected, although the light at the resonant wavelength experiences a π phase shift.
With birefringent material in the cavity, there are two resonant wavelength values, one along the director axis and the other perpendicular to the director axis. If plane polarized light impinges on the structure at 45 degrees relative to the director axis, the electric field vector has components of equal magnitude along the director axis and perpendicular to the director axis. If the wavelength of the light is such that one of the components is resonant, then that component experiences a relative phase shift of n with respect to the perpendicular component, which is not resonant. This means that the input polarization of the light is rotated by π/2 upon reflection, if only one of the components is resonant.
More generally, if the radiation falling on the reflective birefringent Fabry-Perot is polychromatic but plane polarized, then only that wavelength component which is resonant with one of the cavity resonances will experience a polarization transformation. The rest of the wavelengths will experience no polarization rotation. More complex polarization rotation will be experienced depending on the angular relationship between the principal polarization axis direction and the direction of the fast axis of the birefringent material. This transformation can be calculated using Muller matrix calculations or Jones matrix calculations.
An inventive aspect of the reflective Fabry-Perot according to the invention, namely with an electrically alterable birefringent material in the cavity, is that the operable resonant wavelength ωd can be tuned. This is accomplished by changing the effective birefringence of anisotropic material contained in the cavity. The birefringence can be changed conveniently when liquid crystals are used, because the orientation of the liquid crystal molecules can be changed by applying an electric field. The change in orientation in turn changes the optical path length in the cavity. The optical length of the path between the reflectors 32, 34, for polarized light at the applicable orientation, is thus changed as a function of the electrical input signal, electrically controlling the specific wavelength ωd to which the Fabry-Perot is tuned.
For the case where the molecular orientation is parallel at both surfaces, the application of an electric field to the liquid crystal changes only one of the path lengths applicable to the mutually perpendicular polarization components of the input beam. The application of an electric field across the liquid crystal may cause a non-uniform re-orientation of the molecules across the thickness of the cell, but the total optical path length is nevertheless changed, and the total optical path determines the cavity resonance wavelength ωd.
The application of an electric field for tuning does not re-orient or change the direction of the slow axis or the fast axis of the birefringent medium. Thus it is possible to arrange polarization diversity or selective polarization orientations in a manner that remains at the relative orientations for which the device is designed. Only the path length along the fast axis is changed, as long as the liquid crystal structure is untwisted. For twisted nematic liquid crystals, the reflective Fabry-Perot still behaves like a linear waveplate for near resonant wavelengths, because the eigenmode of the Fabry-Perot is always linear. However, the situation is more complex. Such devices may have distinct advantages (i.e., other useful applications).
Thus, for the untwisted sample being discussed so far, light falling on such a structure which is linearly polarized at 45 degrees with respect to the rubbing axis (the slow axis), will experience a 90 degree rotation of the polarization due to the relative π phase shift, as long as the wavelength of the light is resonant with one of the cavity resonances.
The discussion above has applied substantially to Fabry-Perot etalons comprising paired mirrors around a birefringent cavity. It is possible to apply a number of the same inventive aspects to optical interferometers other than Fabry-Perot interferometers.
The structures described here can be used not only for polarization encoding of wavelengths by impinging the light at 45 degrees to the fast axis of the tunable birefringent element, but also for introducing wavelength dependent phase when the device is used so that the light impinges on the device with linear polarization axis at zero degrees with respect to the fast axis of the device. While the operation is polarization sensitive, which may be preferred in certain applications, the device can also be made polarization insensitive by using a diversity scheme. The introduction of phase variation as a function of wavelength is needed for a variety of applications to correct for dispersion compensation, especially in the area of optical communications.
An optical interferometer generally divides light into at least two beams, and the phase of at least one beam can be adjusted. When these beams are combined together, the difference in phase results in interference effect. In general, the phase difference is wavelength dependent, thus the interference effect can be used to select the wavelength to be transmissive or reflective, such as with a Fabry-Perot type interferometer, but also with other devices that function in a similar manner, such as a ring resonator interferometer.
If birefringent material is provided in the light path where the phase can be adjusted (i.e., linearly and/or circularly birefringent material), the phase difference is not only wavelength dependent, but also is polarization dependent. This describes the reflective Fabry-Perot elements described above, and also can be considered a general case according to the invention.
As to the resonant wavelength, only one polarization component is truly resonant, and only that component accumulates the additional phase delay. The orthogonal polarization component is not in fact resonant, even though it may be at the same wavelength as its orthogonal counterpart, and no additional phase is obtained for this not-in-fact-resonant component. Because of this phase difference between the two orthogonal polarization states, the optical interferometer behaves like a (linear and/or circular) waveplate. The type of the waveplate depends upon the characteristic polarization of the interferometer.
For a Fabry-Perot, the eigen polarization state is always linear. Therefore, the reflective birefringent Fabry-Perot always behaves like a linear birefringent waveplate. On the other hand, in a ring resonator interferometer, the characteristic polarization in general can be any polarization, not necessarily linear. As a result, a different sort of waveplate function results.
Several reflective Fabry-Perot resonator devices were constructed as discussed herein as examples using commercially available E7 nematic liquid crystal in a resonant cavity between dielectric mirrors in the infrared region and gold coated surfaces as the "complete" reflectors or at least as high reflectivity dielectric mirrors. These devices were tested. In addition the devices were modeled mathematically and a program simulating results obtained with variation of the variables was prepared and compared to the experimental results.
In one example for which certain measurements are shown in the drawings, the mirror reflectivity was chosen to be 90% for the initial mirror 32 and about 99% for the second mirror 34. The mirror coatings were deposited on top of a conductive indium-tin-oxide coating, coupled to electrodes for applying the electric field across the liquid crystal. On top of the mirror coatings, a thin layer of polymer alignment coating was deposited, using standard spinning techniques, to promote liquid crystal alignment. The samples were rubbed or buffed in a chosen direction and assembled into a cell using precision fiber spacers for controlling the gap of the cell at a nominal gap of 10 microns. Care was taken to ensure that the rubbing direction on the two surfaces were as parallel as possible, including rubbing in opposite directions (parallel and anti-parallel) to prevent pre-tilt and so as to minimize any optical mode mixing due to deviation. The devices were tested at ambient room temperature.
An experimental setup with a polarization beam splitter 50 similar to the setup shown in FIG. 4 was employed for measurement purposes. The input light was delivered through a fiber graded index rod lens and the output lens was collected through a similar lens. The input light was passed through the polarizing beam splitter 50, which served both as a method of polarizing the input light and also as a method of deflecting the resonant reflected light for amplitude measurement. The optic axis of the liquid crystal was aligned at 45 degrees to the input polarization. For purposes of demonstration, a multimode fiber was used. The input light was provided by a broad band light emitting diode and the deflected light was monitored using a spectrum analyzer. A voltage signal was applied across the liquid crystal was a 10 kHz square wave with amplitude varying from 0 to 10 V rms provided by a programmable waveform generator.
The results of the measurements are shown in FIGS. 14-16. In the figures the lowest scan is at zero field and the maximum is at a control voltage of 10 V. At relatively lower voltages, for polychromatic light falling on the structure, one observes two sets of resonances. None of these resonances changes below a certain voltage, called the Freiedrick's voltage, which is evident in FIGS. 14 and 15. This is because there is no molecular re-orientation below this threshold voltage. Above this voltage, one of the resonances changes with the applied electric field. With further increase in the applied voltages the two cavity resonances approach each other and the traces show a limit function behavior wherein the two cavity resonances would coincide at infinite voltage.
Higher modes are also observed, which can be eliminated by choosing the appropriate values of the birefringence and the thickness of the cavity as discussed below. The higher modes are clearly evident near zero volts applied voltage intensity, corresponding to the lowest scans in the FIG. 14, where the resonance at about 1.526 microns is due to the short axis and the other two are for the long axis with one being the higher order mode.
The modes can overlap, which is seen clearly in FIGS. 15 and 16, corresponding to the first and second crossing. When the modes overlap at a particular wavelength, the device effectively is polarization insensitive. The effective birefringence disappears and so does the polarization rotation mechanism due to the differential a phase shift otherwise provided only to one of the components. Both components are affected or unaffected equally.
The disappearance of effective birefringence at the crossings is comparable in FIGS. 15 and 16. Because of the stepwise change of the voltage (in steps of 5 mV), the tests did not contain an iteration in which the voltage was exactly equal to the amplitude that would result in complete extinction of birefringence. However it is clear that at a precise value of the voltage, the reflected signal vanishes, which is to be reasonably expected.
Having experimentally demonstrated the invention, a software simulation was prepared to simulate the performance of the device as demonstrated and to examine operation in the vicinity of the mode crossover. FIG. 17 shows an example of the operator interface permitting selection of values and showing the graphic display output, of the device.
The simulator allows the following parameters to be changed and the results plotted:
1. Wavelength range
2. Slow index value
3. Fast index value
4. Reflectivity of the mirror
5. Sample thickness
The capability of display of multiple graphs was provided, permitting presentation of a series of plots as the value of the fast index is changed in N steps. (Activated by selecting the "series graph" option on the operator interface).
The display also is arranged to plot the results of retardation of the birefringent plate at 45 degrees with respect to the fast axis of the birefringent material in the Fabry-Perot. This function allows the output to be inverted if so desired, by switching between retardation values that differ by π for the double pass. This function is selected using the "switch" option. The switch option is useful to evaluate the performance of non-ideal wave plates in a notch filter, and to obtain different shapes for the wavelength transfer function. The three examples in FIG. 18 show the graphic results of some exemplary simulations, the parameters of which are shown on the operator interface.
FIGS. 19a and b and 20 a and b show the area of the first and second crossings using experimental and simulator calculation forms of output. These appear to correspond closely.
The traces in FIGS. 21a and 21 b are an experimental measurement and a simulation of use of the invention as a notch filter, namely to exclude a tunably controlled wavelength component ωd. This result is obtained, for example, by inserting a quarter wave plate between the polarization separator and the reflective Fabry-Perot in a setup as shown in FIG. 4. The notch filter function can be incorporated into most of the devices that have been described herein, by inserting a polarization rotator at the appropriate position along the beam path, which in essence allows the output polarization to be interchanged, resulting in a (1-T) transfer function, where "T" is the transfer function without the polarization rotation device.
FIGS. 22 and 23 show similar results obtained by cascading the polarization encoding of different wavelengths as demonstrated using the simulator. The beam is simply passed through successive devices, each of which encodes at least one additional wavelength ωd-'n'. Each of the devices also carries forward any polarization encoding caused by the operation of previous stages. The final separation or other decoding at the end of the process is accomplished using a polarization decoder or beam splitter, etc.
In FIG. 22, the reflectivity was set at 99% using the simulator variable inputs, resulting in wider peaks than in FIG. 23, where the reflectivity was 99.6%. The expected results are nevertheless shown. Using a three stage simulation, the three stages were independent.
In the examples illustrating the invention herein, embodiments comprising two spaced planar members have typified the structure of the optical interferometer employed with a birefringent element (preferably a tunable birefringence). It should be appreciated that there are other structural forms for optical interfereometers that can be employed in a similar way. For example, instead of two planar reflectors arranged parallel to one another, three reflectors can be arranged in an equilateral triangle. Alternatively, four reflectors can be arranged in a square or another form of regular polygon can be used with any number of sides. Provided that successive reflectors are closely spaced and/or the light is sufficiently coherent that resonance is established in a cavity comprising at least a portion of birefringent material, the apparatus will function as described with any number of sides. In an example with an effectively infinite number of sides forming a curve back to a coupling point, an optical loop can function as the interferometer as well. In a further example, the reflectors defining the cavity boundaries need not be planar and can be hemispherical or otherwise curved so as to provide optical paths of different lengths as a function of alignment. These and other variations are possible and should be readily practiced in view of this disclosure of examples.
The invention having been disclosed with reference to certain preferred embodiments and examples, it will be apparent to persons skilled in the art that the invention and the concepts it entails and demonstrates can be varied. The disclosure of certain examples herein is not intended to exclude such variations. Accordingly, reference should be made to the appended claims rather than the foregoing description of examples, to assess the scope of the invention in which exclusive rights are claimed.
|Cited Patent
|Filing date
|Publication date
|Apr 28, 1969
|Dec 14, 1971
|Bell Telephone Labor Inc
|Laser mode selection and stabilization apparatus employing a birefringement etalon
|Jul 5, 1979
|Dec 8, 1981
|Agence Nationale De La Valorisation De La Recherche (Anvar)
|Selective optical resonator
|May 1, 1989
|Nov 27, 1990
|At&T Bell Laboratories
|Optical isolator with resonant cavity having gyrotropic material
|Aug 31, 1990
|Nov 26, 1991
|Bell Communications Research, Inc.
|Electronically tunable polarization-independent liquid crystal optical filter
|Mar 29, 1991
|May 5, 1992
|Bell Communications Research, Inc.
|Dual-polarization liquid-crystal etalon filter
|Oct 16, 1990
|Sep 22, 1992
|Bell Communications Research, Inc.
|Tunable liquid crystal etalon filter
|Feb 3, 1992
|Jun 14, 1994
|Nippon Telegraph And Telephone Corporation
|Liquid crystal Fabry-Perot etalon with glass spacer
|Nov 14, 1991
|Jan 10, 1995
|Board Of Regents Of University Of Colorado
|Chiral smectic liquid crystal optical modulators having variable retardation
|Sep 16, 1994
|Sep 19, 1995
|Martin Marietta Corporation
|Etalon with optically polarizing field electrodes
|Nov 5, 1992
|Sep 3, 1996
|Board Of Regents Of The University Of Colorado
|Chiral smectic liquid crystal optical modulators
|May 16, 1995
|Sep 17, 1996
|Jds Fitel Inc
|Chromatic dispersion compensation device
|Nov 30, 1994
|Dec 24, 1996
|The Whitaker Corporation
|Polarization controlled tuneable ring laser
|Nov 21, 1996
|Nov 4, 1997
|Hewlett Packard Company
|Narrow-band tunable optical source
|Dec 12, 1995
|Jan 20, 1998
|Apeldyn Corporation
|Cavity thickness compensated etalon filter
|Jan 23, 1998
|Nov 30, 1999
|Office National D'etudes Et De Recherches Aerospaxiales Conera
|Pulsed optical parametric oscillator
|Mar 25, 1999
|Sep 26, 2000
|Copner; Nigel
|Interferometric optical device including a resonant optical cavity
|Apr 20, 1998
|Nov 28, 2000
|British Telecommunications Public Limited Company
|Tunable optical device
|Jun 23, 1998
|Mar 20, 2001
|Newport Corporation
|Discrete wavelength liquid crystal tuned external cavity diode laser
|Sep 8, 1999
|Mar 27, 2001
|Chorum Technologies Inc.
|Apparatus for wavelength demultiplexing using a multi-cavity etalon
|Aug 26, 1999
|Apr 24, 2001
|Jds Fitel Inc.
|Optical interleaver/de-interleaver
|B. B. Dingel, and M. Izutsu, "Optical wave-front transformer using the multiple-reflection interference effect inside a resonator," Optics Letters, vol. 22, No. 19, pp. 1449-1451, Oct. 1, 1997.
|L. J. Cimini, Jr., L. J. Greenstein, and A. A. M. Saleh, "Optical Equalization to Combat the Effects of Laser Chirp and Fiber Dispersion," Journal of Lightwave Technology, vol. 8, No. 5, pp. 649-659, May 1990.
|Citing Patent
|Filing date
|Publication date
|Jan 23, 2002
|Dec 9, 2003
|Xiaotian Steve Yao
|Frequency locking of tunable lasers by using a birefringent optical cavity
|Jun 27, 2002
|Feb 10, 2004
|Jds Uniphase Corporation
|Rhomb interleaver
|Dec 10, 2001
|Oct 24, 2006
|Optellios, Inc.
|Polarization encoder device
|Dec 11, 2006
|May 3, 2011
|Fujitsu Limited
|Wavelength locker
|Dec 10, 2001
|Jul 11, 2002
|Patel Jayantilal S.
|Polarization encoder device
|Jun 27, 2002
|Jan 9, 2003
|Hulse Charles Andrew
|Rhomb interleaver
|Jul 10, 2006
|Mar 29, 2007
|Kabushiki Kaisha Topcon
|Laser oscillation device
|Dec 11, 2006
|Feb 28, 2008
|Fujitsu Limited
|Wavelength locker
|Oct 20, 2008
|Apr 29, 2010
|Raab, Volker, Dr.
|Oct 20, 2009
|Apr 29, 2010
|Volker Raab
|Polarization coupler
|U.S. Classification
|International Classification
|Cooperative Classification
|European Classification
|Sep 14, 2001
Owner name: OPTELLIOS, INC., NEW JERSEY
Free format text: CHANGE OF NAME;ASSIGNORS:PATEL, JAYANTILAL S.;ZHUANG, ZHIZHONG;REEL/FRAME:012174/0802
Effective date: 19991115
|Mar 14, 2007
|Maintenance fee reminder mailed
|Mar 19, 2007
|Surcharge for late payment
|Mar 19, 2007
|Fee payment
Year of fee payment: 4
|Apr 4, 2011
|Maintenance fee reminder mailed
|Aug 26, 2011
|Lapse for failure to pay maintenance fees
|Oct 18, 2011
|Expired due to failure to pay maintenance fee
Effective date: 20110826


text:
New Castle Real Estate
New Castle is located in Alabama. New Castle, Alabama has a population of 72. New Castle is more family-centric than the surrounding county with 100% of the households containing married families with children. The county average for households married with children is 27.84%.
The median household income in New Castle, Alabama is $93,026. The median household income for the surrounding county is $45,415 compared to the national median of $53,046. The median age of people living in New Castle is 59.7 years.
New Castle Weather
The average high temperature in July is 91 degrees, with an average low temperature in January of 34.2 degrees. The average rainfall is approximately 54 inches per year, with 1.7 inches of snow per year.
New Castle Map
New Castle real estate offices
Real estate near New Castle
Nearby Cities
New Castle Zip Codes
Nearby Cities Homes for Sale

subset: commoncrawl


text:
Big Steve's BBQ & Catfish
Duncan, OK 73533
Big Steve's BBQ & Catfish in Duncan is your place to go to satisfy those cravings for some sauce covered,...Learn More
Big Steve's BBQ & Catfish in Duncan is your place to go to satisfy those cravings for some sauce covered,...Learn More
Satisfy your Asian cuisine cravings with a trip to Kyoto in Duncan. Open seven days a week, Kyoto is ready and waiting...Learn More
Special Days Cake Boutique is family owned and operated and located inside the historical Cordell Photography Studio in...Learn More
Phipps Bar-B-Q in Durant serves up heaping helpings of all your barbecue favorites six days a week. Stop by for...Learn More
Tastees Burger in Duncan serves up delicious hamburgers, cheeseburgers and more six days a week. Stop by and dine...Learn More
Whether you're in the mood for chicken enchiladas or a fried freshwater favorite, El Palacio & Captain...Learn More
Cali Burrito is Duncan's stop for fast Mexican food. Conveniently located off the highway, Cali Burrito makes all of...Learn More
Tim's Place in Duncan offers breakfast and lunch, six days a week. Stop by for homestyle favorites like eggs with...Learn More
Jumpstart your morning with a sugary, home baked treat and a steaming cup of coffee at Jitters Coffee House & Sweets...Learn More
Day Break Diner specializes in breakfast, but they also serve a wide variety of lunch items. ...Learn More


text:
Data entry for online store URGENT - repost
This project received 47 bids from talented freelancers with an average bid price of $11 USD / hour.Get free quotes for a project like this
Project Budget$8 - $15 USD / hour
Total Bids47
Project Description
We hope this finds you well,
We require a data entry service as well as content writing for an online shop, could be a potentially on going monthly arrangement if we are satisfied with the work conducted and the speed in which its was completed.
You will be expected to :
-to insert data fast and efficiently
-to make no errors or forget any steps
-to be able to guarantee a certain quantity of work will be completed every day and work on a schedule to complete the task by a due date.
-write short content about products.
-to write in English very well, with no misspellings or error in grammar.
The work is easy but simply requires that you follow each step needed to complete the task requested on any given data entry assignment. Most of it is copy paste work and some content writing skills is necessary. We will do a 1 week trial with a few candidates and offer an ongoing part time job to whom ever performs best.
Skills Required
Looking to make some money?
- Set your budget and the timeframe
- Outline your proposal
- Get paid for your work
Hire Freelancers who also bid on this project
Looking for work?
Work on projects like this and make money from home!Sign Up Now
- Forbes
- The New York Times
- Time
- Wall Street Journal
- Times Online


text:
Added On: • Views: 200 • Duration: 03:44
Categories: Sperm
Tags: Porn Star Spa, Outtie Pussy, MILF, Medium Ass, Massage, Cum on Tits, Bush, Blowjob, Blonde, Big Tits
Description: Sorry, there is no description for this movie
Our site has a zero-tolerance policy against illegal pornography.
All galleries and links are provided by 3rd parties. We have no control over the content of these pages.
We take no responsibility for the content on any website which we link to. Copyright 2014


text:
Companies that remove snow, supply electricity to commercial customers and remove toxins from drinking water were among the 30 local enterprises that were recognized Wednesday night at Providence Business News' fifth Fastest-Growing & Innovative Companies event, held at the Crowne Plaza Providence-Warwick. more
I know that Wright's Farm Restaurant is not everyone's cup of tea. But our menu is very simple; we offer freshly baked rolls, salad, pasta, fries and platters of chicken served family style, with very few exceptions. It amounts to 10,000-12,000 … more
(Updated 12:30 p.m.) Behind Citizens Bank in Providence, between Westminster and Cranston streets, sits a vacant lot. It's the previous home of Louttit Laundry, but after the building was abandoned in 1985, dilapidation was inevitable and the building got … more
By Eli Sherman | firstname.lastname@example.com | 4/21/16
The restaurant review was exuberant in its praise. Joie S. had just visited The Malted Barley, a new restaurant in Providence that features a rich variety of craft beers and hand-rolled, gourmet pretzels. "I AM SO EXCITED THIS PLACE IS … more
By MARY MACDONALD | firstname.lastname@example.com | 4/14/16
Carla Hall, known as a Top Chef finalist and co-host of ABC's "The Chew," told the audience of 1,100 at Bryant University's 19th annual Women's Summit on Friday about the "squirrely path" she took to get to where she is today. more
By Lori Stabile
Wearing a T-shirt emblazoned with the words, "I have the body of a god (Unfortunately it's Buddha)," Paul Gervais, owner of Buddha Belly LLC, leans out the window of his food truck. "Can I get an order of the dumplings, please?" asks a … more
By Eli Sherman | firstname.lastname@example.com | 8/11/16
Twenty Rhode Island restaurants have been honored with Wine Spectator's 2016 Restaurant Awards. more
By Jessica D. Bouchard
Finlay Extracts & Ingredients USA Inc., part of a multinational tea, coffee and horticulture business, is requesting state incentives to build research, manufacturing and distribution facilities at Quonset Business Park. more
By Mary MacDonald
The Providence Board of Licenses is not serving the people at an acceptable required standard and significant changes are necessary. That's according to former R.I. Attorney General Jeffrey Pine, who was commissioned by the Providence City Council in March to review the embattled city board. more
By Eli Sherman
"Sometimes I come up here, put my feet up on the tractor, look out over the sail-boats and think to myself: 'This is Rhode Island,' " said Tyler P. Young, as he gazed across the Sakonnet River toward Aquidneck Island on the last day of … more
By Eli Sherman | firstname.lastname@example.com | 4/28/16


text:
With kids comes stuff. Previously untouched areas of your living room sprout baby swings, high chairs and game consoles; the kitchen cabinets overflow with sippy cups and snacks. Some purchases make good sense (bookshelves), some are indulgent (matching family scooters?) and many are downright silly. But, a precious few are must-haves -- parenting products you love almost as much as the kids themselves.
In honor of Valentine's Day, it's time to show these standout items how much you care, to say thank you for $1.99 wet wipe travel packs and the mother of all mommy saviors: the cellphone.
Of course, not everything needs to cost money. There are songs, catchphrases and communities who deserve a round of applause too. The only rule in this holiday game is that when asked to complete the sentence, "I <3 my _____," you must not say "kids," "husband" or "wife." Because we all love our families -- that's a given -- so for a moment, in the name of sharing a few parenting secrets, give your affection to the STUFF.
Below are answers from the editors of HuffPost Parents. See what they can't live without, then add your own by leaving a comment or tweeting answers to @HuffPostParents with the hashtag #ilovemy.


text:
Enter your Email Address and click 'Continue' Example: firstname.lastname@example.com Submit Cancel Forgot Password Close /GarnetHill/US/Global/Popups/forgot_password Enter your email address
false pdp {"scheme":"product1_cr"}
false pdp {"scheme":"product2_cr"}
Tiered Knit Sundress - Girls is rated out of 5 by 56.
Rated 5 out of 5 by BlessedMomma from So pretty and fun My seven year old loves this blue tiered dress with leggings and a Lavendar ruffle shrug sweater or a denim jacket or sleeveless. She always gets compliments when she wears it. We wash and hang dry her dresses and it keeps well.
Date published: 2016-11-06
Rated 5 out of 5 by thegranoladoctor from Soft and Sturdy I have purchased other "tiered" girls items and this is another good one. Very soft and sturdy. It help up well after a summer of washes. Only downside is that the top of this dress is narrow, so is a little hard for my 5 year old to pull over her head by herself.
Date published: 2016-10-27
Rated 5 out of 5 by happymom7 from great dress! As with other clothing I have purchased from Garnet Hill, this dress is very high quality, looks & feels great, and my daughter has loved wearing it! We even received a hand-me-down one of different colors from a friend, and it looked great even after many washings. Now, we've had 2 to enjoy!
Date published: 2016-10-27
Rated 5 out of 5 by kmrb from Excellent Girls Dress This dress, and the tiered skirt, are some of our daughters favorites! The colors are bright, the cotton is soft, and there is a nice twirl effect. They reach for these all spring, summer and into fall. It also looks great over leggings or tights when it gets cooler!
Date published: 2016-10-26
Rated 5 out of 5 by savannahpirate1 from Twirl-worthy dress My granddaughter loves these dresses! They come out of the washer and dryer looking great....nice fabric, no "itchies" and still look good after a day at day care. We got this one on sale, so it was an especially good deal. Ample room to wear for a good amount of time.
Date published: 2016-08-10
Rated 5 out of 5 by Niia from Cuteness overload Lovely dress; I love colors, design, fabric, everything is just perfect! Please bring these dresses next year again :)
Date published: 2016-05-25
My daughter is 6 years old - weighs 49 lbs and 48" tall. We will be going on a cruise in August 2015. Which size should I purchase - size 6 or 8?
my daughter is the same height/ weightexactly.. i would get the 6. i have been buying 8 of different dresses in GH and they are too big!
Date published: 2015-08-01
Would someone please recommend a size (8 or 10) for a 9 yr old who is 55 inches tall and 65 lbs. She is rather slim. Thanks!
In looking at the information given for height, weight and the fact that she is slim, we think the 8 will be best for her.
Date published: 2014-04-10
My daughter turned 3 in December. She weighs 27 lbs and is 33 inches tall. What size do you recommend for the summer - a 2 or 4?
We recommend size 2.
Date published: 2016-02-26
My daughter is 38" tall and 32 lbs, should I order a size 2 or a size 4?
WIth the measurements given, we would recommend the size 4. It will give her some growing room as well!
Date published: 2015-03-31
Can you please tell me how long size 6 is? Thanks
The length for size 06 is 25.5".
Date published: 2016-06-02
Product:31089-Tiered Knit Sundress - Girls


text:
Regional North America United States Society and Culture Politics Parties Republican
This category holds links for national committees, affiliated and auxiliary organizations, and fan pages of the Republican Party, the primary center-right political party in the United States. The Party is often referred to as the GOP, or Grand Old Party, and its symbol is the elephant. The Republican Party was founded in 1854 by members of the Free Soil Party and the Conscience Whigs-- members of the Whig Party from the North so called because of their then-radical opposition to slavery. The election of Illinois Republican Abraham Lincoln in 1860 firmly established the Republican Party as a major force in American politics. Other Republican Presidents include Ulysses S Grant, Theodore Roosevelt, Dwight Eisenhower, and Ronald Reagan.
Subcategories 14
Related categories 2
Sites 17
Republican National Committee
Official Internet home of the Republican National Committee. Updated daily with news and commentary from the RNC.
Seeks more aggressive environmental regulation among Republican lawmakers, and supports candidates who favor environmental regulation.
Political action committee recruits and trains new candidates, campaign staff and activists. Features campaign information, training tapes [MP3], events and volunteer opportunities.
Homeschool Republican
Organization of citizens aged 12 and up who are dedicated to supporting and pledging time to candidates. Features a platform.
Moderate Republicans
Weblog of news and information from a man who wants to "bring the Party of Lincoln back to its roots."
National Teen Age Republicans
Site of the national office of TARS, featuring links to clubs, list of resources and publications available, and leadership conference information.
Republican Discussion Forum / RDF
Boards available on various topics.
Republican Governors Association
Newsletters, radio clips and other information about Republican governors.
Republican Jewish Coalition
Jewish Republican lobby group.
Republican Liberty Caucus
A grassroots, nationwide organization affiliated with the Republican Party (GOP). The goal of the RLC is to elect pro-liberty individuals to office.
Republican Main Street Partnership
Party members and public officials committed to building a principled but pragmatic center within the party. Features a legislative agenda, volunteer opportunities and news.
Republican National Hispanic Assembly
National outreach organization of the Republican Party
Republican National Lawyers Association
A network of Republican attorneys who assist Republican groups, candidates, and office holders with pro bono legal services and through party-building activities. Site lists events, committees, and membership information.
Republican State Leadership Committee
National Section 527 group working to elect down-ballot, state-level Republican officeholders through recruiting candidates and providing research, financial support, and assistance in message development and delivery.
Republican Youth Majority
A national network of moderate to liberal Republican youth.
Republicans for Choice
Pro-choice group within the Republican Party.
Theocracy Watch
A non-profit public information group committed to exposing the rise of the radical religious right as a political force in the Republican Party.
Last update:November 17, 2016 at 6:24:05 UTC
All Languages


text:
Ice-Watch Ice Sili Stone Black Ladies Watch STBSSS09
Ice-Watch Ice-Classic Solid Big Purple Mens Watch CSPEBP10
Ice-Watch Multifunction Stone Ladies Watch MFBSSS10
Ice-Watch Purple Stone Tycoon Unisex Watch STPSUL10
Find us on social media:
Jacobtime is not an authorized dealer for any company, due to our extremely low pricing. All of our watches are 100% authentic and brand new. We offer a 2 year Jacobtime Warranty on all watches.


text:
It is utterly logical for polygamy rights to follow gay rights.<quoted text>Hell no. It's a rationalization, not logical reasoning.
There are too many steps in between to claim it logically follows.
If traditional marriage is defined as the union of two people of opposite gender, and if the gender requirement is nothing but prejudice, exclusion and an arbitrary denial of one's autonomous choices, then the number requirement (two and only two), is a similarly arbitrary, discriminatory and indefensible denial of individual choice.


text:
White House touts Obamacare payment info that chops down enrollment number they just celebrated
**Written by Doug Powers
President Obama took a "victory lap" this week because enrollment in Obamacare had supposedly gone over the seven million mark.
Yesterday, Blue Cross said that 80 to 85 percent of people enrolling in an Obamacare plan have paid their premiums. That prompted more White House partying:
latest ACA conspriacy theory collapses MT: @sarahkliff BlueCrossBlueShield says that state plans are hovering around 80-85% of premiums paid
— Eric Schultz (@Schultz44) April 2, 2014
Alternate version: "Hooray! The 7.1 million number we're celebrating is nowhere near factual!"
From National Journal:
One of the biggest players in Obamacare's exchanges says 15 to 20 percent of its new customers aren't paying their first premium–which means they're not actually covered.
The latest data come from the Blue Cross Blue Shield Association, whose members—known collectively as "Blues" plans—are participating in the exchanges in almost every state. Roughly 80 to 85 percent of people who selected a Blues plan through the exchanges went on to pay their first month's premium, a BCBSA spokeswoman said Wednesday.
The new statistics, particularly from such a large carrier, help define how many people are actually getting covered under the Affordable Care Act.
If the nationwide payment rate, across all carriers, remains at 80 to 85 percent, the 7.1 million sign-ups Obama announced Tuesday would translate into somewhere between 5.7 and 6 million people who are actually covered.
And how many of those few million had insurance but lost it because of Obamacare regs? No matter — break out the party hats! And remember, the debate is over.
**Written by Doug Powers
Twitter @ThePowersThatBe
Necessary reminder for MSM: 'Death to America' chants in Iran started WAY before Trump became president
February 10, 2017 01:16 PM by Doug Powers
Now that Obama's gone it's safe for the MSM to notice Iran's 'more powerful' than they've been in decades
February 6, 2017 08:16 PM by Doug Powers
Fifty Shades of Grey Lady: NY Times Mag troubled by 'uncomfortable love affair' on Super Sunday (open thread)
February 5, 2017 09:45 AM by Doug Powers
Ex-Prez who took nuns to court slams Trump on religious freedom
January 30, 2017 07:13 PM by Doug Powers
Perfect: Richard Branson sends private jet for Obamas so they can discuss how everybody's going to die from fossil fuel emissions
January 24, 2017 09:21 AM by Doug Powers
Categories: Barack Obama, Enviro-nitwits, Feature Story


text:
The author of several past Proceedings articles from hot spots around the world files this report from Mombasa.
This content is only accessible by current members. Please login to
view the full content.
Today [4]
Mr. Axe is a freelance writer based in Columbia, South Carolina. His writing has appeared in The Village Voice
None found for this author.


text:
Videos of Panel Presentation
Waves of Despair, Tides of Hope
August 29, 2012
A panel presentation by Japanese municipal government officials who participated in the March 2011 tsunami response and recovery efforts in Japan.
- Masayuki Nawa, General Affairs & Planning Dept, General Affairs Division, Miyako City, Iwate Prefecture, Japan: Tsunami damage at Miyako City and evacuee behavior
- Junichi Matsuo, Fire Department, Prevention Division, Sanda City, Hyogo Prefecture, Japan: Importance of local disaster prevention capability in the East Japan great earthquake disaster: Learning from activities in Minami Sanriku city
- Hiromasa Konnoh, General Affairs Department, Sakuragawa City, Ibaraki Prefecture, Japan: Lessons learned from the case of registered tangible cultural properties
At the beginning of the presentation, the first presenter, Mr. Nawa, showed a powerful video of Tsunami that struck his town. View the tsunami video >>
English Version