Long wave infrared liquid crystal tunable thin film filter

A long wave infrared liquid crystal tunable thin film filter operating in the 8 to 12 mum spectral region is presented in this thesis for a high throughput free space optical communication system. A cavity consists of reflector layers, comprised of alternating Germanium and Barium Fluoride thin films, and an E7 liquid crystal layer. By coupling multiple cavities using a Germanium thin film, a desired transmission profile can be achieved. An optimum number of cavities were selected to minimize coupling distortion while maintaining the desired transmitted output profile. This thesis shows that coupling three cavities results in an optimum transmitted output. The three cavity design results in the magnitude of the output distortion from -0.16 to -1.29 dB and a full width half maximum from 2.7 to 9.5 nm across the 8 to 12 mum spectral region.