Plasmonic attenuator for infrared imager testing

Robert E. Peale; Pedro N. Figueiredo; Justin R. Phelps; Kevin C. Chan; Reza Abdolvand

doi:10.1117/12.2618485

27 May 2022 Plasmonic attenuator for infrared imager testing

Robert E. Peale, Pedro N. Figueiredo, Justin R. Phelps, Kevin C. Chan, Reza Abdolvand

Proceedings Volume 12106, Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXXIII; 121060L (2022) https://doi.org/10.1117/12.2618485
Event: SPIE Defense + Commercial Sensing, 2022, Orlando, Florida, United States

Abstract

We describe a variable attenuator for use with conventional IR quantum cascade or carbon dioxide lasers to create a source with widely and rapidly controllable effective radiant temperature. This would have application to testing of imagers, which must observe scenes that change rapidly between ambient background and very hot objects. The mechanism is controllably frustrated surface plasmon resonance. The device comprises an IR transparent prism with one face coated by a semitransparent (optically-thin) semiconductor having suitable infrared plasma frequency, followed by a controllable gap to a conventional metal mirror. For the mid-wave infrared band (MWIR, 3-5 micron wavelength), we consider a sapphire hemicylindrical prism coated with the transparent conductor gallium-doped ZnO (GZO). For the long-wave infrared band (LWIR, 8-12 micron wavelength), we consider an undoped-Si prism with one heavily-doped surface. Due to the exponential decay of the surface-plasmon-polariton evanescent wave above the conducting film, the log of internal reflectance of the conducting film decreases linearly with increasing gap, typically by about 1 decade per micron, with a total variation of over 5 orders of magnitude. The effective radiance is determined by laser intensity, reflectance, and reflected-beam divergence. Comparison of the effective radiance values to the band radiance of a black body indicates effective radiant temperatures that can be varied from 300 to over 4000 K for a mirror diameter of 100 (MWIR) or 650 (LWIR) microns. At low effective radiant temperature the device can provide 0.1 K resolution.

Conference Presentation

Citation Download Citation

Robert E. Peale, Pedro N. Figueiredo, Justin R. Phelps, Kevin C. Chan, and Reza Abdolvand "Plasmonic attenuator for infrared imager testing", Proc. SPIE 12106, Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXXIII, 121060L (27 May 2022); https://doi.org/10.1117/12.2618485

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