Tunable IR filters using flexible metallic microstructures

Abstract

Revolutionary advances in infrared (IR) imaging and sensing technology would be possible if focal plane tunable filters with high transmission, wide acceptance angles, and wide tunability were available. Tunable high-pass transmission filters are ideally suited for enhancing the capability of optical detectors and imaging systems. Most optical detectors have a characteristic low-energy cutoff, set by the energy bandgap or photoemission threshold of the detector material. A tunable high-pass frequency filter would allow variation of the long-wavelength cutoff over the useful wavelength range of the detector material. The decrease in detector output as the filter cutoff wavelength is decreased would provide direct measurement of the spectral content of the radiation causing the detector response. Thus, conventional broadband detectors and imagers could be programmed to give spectral information as well as total intensity information.