Improved and Tuanble Infrared Rugate Filters

Rugate Technologies, Incorporated, proposes to develop improved narrow notch and tunable Rugate filters for the infrared. Four problems are addressed in this study: (1) identification of Rugate material pairs for use in the far infrared (out to 30 microns); (2) development of polarization and non-polarization sensitive narrow notch filters, as well as control of sensitivity to incidence angle; (3) novel filter designs; and (4) wavelength tunable filters. Rugate filters use the blending ratio of two materials of different refractive index to produce a continuously varying, periodic index profile. Typical IR materials used to date are limited in spectral range. New materials will be sought to extend the present far IR limit out to 30 microns. Techniques for controlling the sensitivity of the film to polarization and field of view will be developed. Wavelength tunable filters are a keen interest. Limitations in current methods of tuning notch position will be studied and new approaches developed. In Phase 1, we will execute material studies on blended materials pairs, and develop new design techniques. In Phase 2, we will fabricate prototypes of the more promising designs.