Narrow-Band Wide Field-of-View Filter Study
Final rept. 7 Jul 80-30 Oct 81
ROCKWELL INTERNATIONAL CORP THOUSAND OAKS CA SCIENCE CENTER
Pagination or Media Count:
With the advent of free space laser communicationss, and communication to submerged submarines in particular, the state-of-the-art in narrowband wide field-of-view spectral filters is being pushed to its limit. In the case of underwater communication, the combined effects of absorption and scattering result in a radiance function of large angular extent. Conventional narrowband filters simply do not have suitably large angular fields-of-view to receive light from the full range of angles encountered. A shift of the transmission passband with angle of incidence leads to a decrease of signal transmission and proportionally larger background intensity. It was recently realized that a material modification of traditional birefringence interference filters, by using materials having large dispersion in birefringence near an isotropic point, could result in compact, narrowband filters having a dramatically increased field-of-view. Under this contract the development of a dispersive birefringence filter was pursued both theoretically and experimentally. This study of birefringence filters at extremely large angles of incidence has stimulated additional work to study the effects of sheet polarizers and conventional waveplates under these conditions. The developments in dispersive birefringence filters represent a major jump in the capabilities of narrowband spectral filters. Literature surveys and subsequent laboratory studies have led to the identification of potential dispersive birefringence materials which may extend the spectral range of operation to both shorter and longer wavelengths.
- Non-Radio Communications