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Proceedings Paper

Development of tunable longwave infrared filters based on guided-mode resonance
Author(s): Neelam Gupta; Mark S. Mirotznik; Robert Magnusson
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Paper Abstract

We describe development of spectrally tunable micro-engineered filters operating in the longwave infrared (LWIR) region from 8 to 12 μm based on using the guided-mode resonance (GMR) effect. The device structure consists of a subwavelength dielectric grating on top of a homogeneous waveguide using high index dielectric transparent materials, i.e., germanium (Ge) with a refractive index of 4.0 and zinc selenide (ZnSe) substrate with refractive index of 2.4. The filters are designed to reflect the incident broadband light at one (or more) narrow spectral band while fully transmitting the rest of the light. The tuning of the reflection wavelength is achieved by changing the angle of incidence of light by mechanically tilting the filter. Filters based on one-dimensional gratings are polarization dependent and those based on two-dimensional gratings are polarization independent at normal incidence of light. Both 1-D and 2-D gratings were designed and characterized. Anti-reflection coatings were applied on substrate interfaces to improve transmission over the entire spectral region. We carried out transmission measurements of these filters using an automated tunable room temperature quantum cascade laser (QCL) system operating from 7.3 to 12.9 μm, and a modified Fourier Transform Spectrometer with a custom designed chamber for normal incidence of light on the sample. We present detailed characterization experiments and compare the theoretical and experimental results.

Paper Details

Date Published: 26 February 2020
PDF: 9 pages
Proc. SPIE 11284, Smart Photonic and Optoelectronic Integrated Circuits XXII, 112840N (26 February 2020); doi: 10.1117/12.2545136
Show Author Affiliations
Neelam Gupta, U.S. Army Research Lab. (United States)
Mark S. Mirotznik, Univ. of Delaware (United States)
Robert Magnusson, The Univ. of Texas at Arlington (United States)

Published in SPIE Proceedings Vol. 11284:
Smart Photonic and Optoelectronic Integrated Circuits XXII
Sailing He; Laurent Vivien, Editor(s)

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