Very Large Solar Rejection Filter for Laser Communication

Surface Optics Corporation (SOC) will develop a band pass filter comprised of a visible dielectric mirror and an induced transmission filter, applied to two sides of a cast polyimide membrane. The mirror/filter combination will block 95% of the incident solar radiation, while allowing a narrow pass-band for YAG laser communication. The combination of a visible dielectric mirror constructed on one side of a membrane and a band-pass filter on the second surface, offers a means of creating a very efficient solar reflector with relatively few coating layers. The exceptionally thin and flat optical substrate will minimize degradation of the laser signal. Meter-class membrane filters are sought by NASA to prevent over-heating of ground-based laser communication receivers operating during daylight hours. In Phase I, induced transmission filter designs based on both silver and germanium films will be evaluated for overall filter performance. Small filters will be constructed and measured for optical performance and agreement with predictions. In Phase II, the best designs will be applied to large membrane substrates approximately 2-m in diameter.