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Photonics in security systems

When exploring the role of photonics in security systems, a sentence from the novel Effi Briest written by Theodor Fontane comes to mind: It’s so hard, what to do and what to leave. This is too big a subject.1 Indeed, security is a big subject of our contemporary life. Its significance depends on the system context: cyber space, authentication, communication infrastructure, transportation, disaster management, forensics, surveillance, environmental protection, to name just a few examples. In each field photonics plays an important role in its ability to provide diagnostic tools with high sensitivity and selectivity. Especially, the possibility to separate spatially the information gathering interaction from the processes of detection and information extraction makes photonics an ideal tool for non-contact and remote sensing. It was our task as guest editors to narrow down the big subject into a few topics in order to present a comprehensible collection of papers. Biased to some extent by our own area of expertise we invited colleagues working in the fields of hyperspectral and active spectroscopic sensing, autonomous vehicle navigation, optical materials manufacturing, and electronics to contribute to this special issue of photonics in security systems. Securing those places where people meet and interact such as transportation hubs or public areas without encroachment on the general personal rights is a task of immanent importance for every society worldwide. Video surveillance to monitor structural changes and the behavior of people is very popular. In the future, imaging in the visible spectral band will be supplemented by hyperspectral recording and processing of information to generate additional features for the classification of events. Helge Bürsing and Wolfgang Gross from the Fraunhofer IOSB lead into the series of papers with a short tutorial on hyperspectral imaging techniques and security related applications. Information about the chemical nature of substances dispersed in the air or contaminating surfaces will become available through the application of spectroscopic remote sensing techniques. The infrared spectrum covers the so-called fingerprint region of most hazardous substances and is therefore well suited for spectroscopic classification. The letter of Kenneth Hay and colleagues from Cascade Technologies/Emerson Process Management and the Swedish Defence Research Agency describes an open path analyzer based on quantum cascade laser intra-pulse absorption spectroscopy and a related system concept for the detection of gas plumes emanating from illicit manufacturing sites of an improvised explosive device. The research paper by Frank Duschek and co workers from the German Aerospace Center, Institute of Technical Physics, and the Friedrich-Loeffler-Institute, Institute of Bacterial Infections and Zoonoses, presents a stand-off sensor applying laser-induced fluorescence to detect and classify bacteria suspended in the atmosphere at distances from 20 m up to 100 m. Active mid-infrared hyperspectral imaging and backscattering spectroscopy of contaminated surfaces is the topic of the contribution by Jan Jarvis and collaborators from the Fraunhofer-Institutes for Applied Solid State Physics IAF and Optronics, System Technologies and Image Exploitation IOSB. They use a wideband tunable external cavity quantum cascade laser and a novel background extraction algorithm based on the adaptive target generation process in order to acquire and analyze the data. In the succeeding triplet of papers researchers from Thales Research and Technology together with partners from other institutions share their insight into infrared component technologies. In a common effort, François Gutty, his coworkers from Thales Research and Technology TRT, the III-V lab, and the Fraunhofer IAF developed a high peak-power laser system tunable from 8 to 10 μm by amplifying the radiation of a broadly tunable external cavity quantum cascade laser in an optical parametric *Corresponding author: Hans Tholl, Diehl Defence, Überlingen, Germany, e-mail: hans.tholl@diehl-defence.com Heinz-Wilhelm Hübers: German Aerospace Center (DLR), Germany 1 Theodor Fontane (1819–1898) was a German journalist, novelist and poet. The sentences are from chapter 15 of his novel Effi Briest and read in the original German language: “Es ist so schwer, was man tun und lassen soll. Das ist auch ein weites Feld”. One of the guest editors (HDT) provided the translation, fully aware of the fact that the context of the conversation between Effi Briest and her father might suggest a different view.