Optical Filter for Undersea Blue-Green Laser Communication

We propose to build a seven-filter array of wavelength selectable wide field Lyot filters. Each filter will have a hexagonal aperture of 100 mm in the largest dimension and the total clear aperture of the array will exceed 390 cm^2. All filters will have a passband full width at half maximum of approximately 0.3 nm at a wavelength of 532 nm and a free spectral range between adjacent passbands greater than 10 nm. We will provide six of these filters under the base contract and the seventh under the option. The seventh filter will have as an added function 3 selectable passband widths of 0.15nm, 0.3 nm and 0.6 nm. Liquid crystal elements accomplish all wavelength selection and passband width selection functions non-mechanically. We will also investigate the use of a high index birefringent crystal under the option to expand the angular field of view in future filters.