Long Wave Infrared Acousto-Optic Materials:Development of Novel Materials for the Fabrication of LWIR (8-12 micron)Acousto-optic Tunable Filters for I

We propose to develop novel anisotropic materials that can be used to fabricate acousto-optic tunable filter (AOTF)-based spectral imaging systems in the LWIR (8 to 12 micron) spectral region. AOTF's are very attractive for multispectral and hyperspectral applications such as the detection of targets, backgrounds, and stand-off chemical and biological agents. Tellurium dioxide (TeO2) is the most commonly used AOTF material, and it has a spectral transmission range of 0.35-5.0 micron. However, chemical agent infrared absorption/emission primarily occurs in the 8-12 micron wavelength region. Currently, there is no technologically matured material for AOTF imaging in this wavelength range. Thus, we propose to investigate the mercurous halides (Hg2Cl2 and Hg2Br2) and tellurium (Te) for this purpose. These materials can be processed at relatively low temperatures, are nonhygroscopic, have high acousto-optic figure of merit (M2), high birefringence and relatively high transmission in the 8-12 micron spectral range. This long wave infrared (LWIR) region technology is relevant to the detection of buried mines and is an essential part of achieving the goals set forth in the Army's Third Generation Science and Technology Objective (STO).