NARROWBAND OPTICAL FILTER FOR LASER RADAR APPLICATIONS

The objective of the proposed program is to develop a widefield narrowband optical filter (WNOF) for use in laser radar receivers. The WNOF provides the necessary discrimination against strong solar bandground that limits the daytime performance of the laser radar system. The proposed approach is based on a new design of field widened birefringent filter. Preliminary analysis shows the following performance goals can met: bandwidth = 0.5A, field of view = +/- 7.5 degrees, optical aperature = 6.5 cm, tranmission = 20 percent, and can be designed to match a selected laser wavelength anywhere in the green wavelength region (510 - 550 nm). A number of critical issues for the proposed approach are identified. These include the need of fine tuning for compensating thermal effect and fabrication errors, reduced optical transmission due to fresnel loss, polarizers and additional loss from electro-optic elements. A risk reduction effort is proposed in Phase I that includes these tasks: (a) analyze proposed WNOF design and method of tuning, (b) investigate the issues associated with production of the filters and (c) development of a single stage prototype for demonstration of the tuning of the filter.