Narrow Band, High Reflectivity Optical Elements in the Infrared

Fabrication of narrow band, far infrared (FIR), high reflectivity optical elements (notch filters) requires development of an interference filter that is approximately ten times thicker than standard FIR interference filters. In Phase I we developed designs capable of meeting 2% bandwidth FIR filters using rugate techniques. We selected high refractive index materials to minimize filter performance shift with angle of incidence and minimize thickness and demonstrated thick film deposition capability of the selected materials. In Phase II, we will develop the capability of depositing thick blended films (two or more materials), select the most effective average index, and deposit single notch filters, of decreasing bandwidth. Key to success of Phase II will be full development and integration of our deposition control system and optical monitor. Filters will be characterized for optical performance, environmental durability, and laser damage threshold.