15 May 2008 Design and fabrication of efficient miniature retroreflectors for the mid- and long-range infrared
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We report our progress on the design, modeling, and fabrication of a step-index miniature spherical retroreflector for use in the mid- and long-wave infrared region (3 μm-12 μm). Efficient retroreflectors with large acceptance angles and isotropic performance have several defense applications - for instance, target tracking and monostatic LIDAR. The ideal isotropic spherical retroreflector is epitomized by the spherical Luneburg lens, which brings a collimated beam to a perfect focus on the rear surface of the sphere due to its gradient index profile and spherical symmetry. The ideal Luneburg lens' gradient profile, however, must have an index value equal to that of the immersion medium at its boundaries; therefore, rendering its fabrication infeasible for applications in air. Although spherical gradient index designs can provide a good approximation of the Luneburg lens, as of now there have been no demonstrated methods of fabricating such lenses, especially for mid- and long-wave infrared applications. Consequently, we have designed a retroreflector with a step-index approximation to a spherical gradient index design with comparable optical performance to the spherical gradient index ideal. This retroreflector design can be fabricated by molding a higher index chalcogenide glass shell as a cladding layer over a lower index core such as ZnS using glass compression molding.
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Bruce E. Bernacki, Bruce E. Bernacki, Norman C. Anheier, Norman C. Anheier, Kannan Krishnaswami, Kannan Krishnaswami, Bret D. Cannon, Bret D. Cannon, K. Brent Binkley, K. Brent Binkley, "Design and fabrication of efficient miniature retroreflectors for the mid- and long-range infrared", Proc. SPIE 6940, Infrared Technology and Applications XXXIV, 69400X (15 May 2008); doi: 10.1117/12.771410; https://doi.org/10.1117/12.771410

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