Ultra-High Dynamic Range Optical Modulators For Ladar Scene Projection

Scene Projectors enable improvements in the design and testing of LADAR systems, including full “hardware in the loop” testing, and require a large number of pixels whose intensity can be rapidly varied over an optical dynamic range exceeding 62 dB. Typically, such Scene Projectors may consist of a 256 x 256 array of pixels that can be modulated at rates approaching several gigahertz. One approach being investigated for the eye-safe wavelength of 1550 nm, employs a cw laser source with an array of external intensity modulators. Several hundred modulators can be fabricated on a single 4-inch lithium niobate wafer. Commercial optical intensity modulators have extinction ratio (ER) values between 20 and 30 dB, which is satisfactory for their intended applications. During the Phase I program, SRICO developed the world’s first optical intensity modulator based on a lithium niobate Mach-Zehnder Interferometer that has an ultra-high ER in excess of 62 dB - over one thousand times greater than provided by most commercial modulators. The Phase II program will develop and demonstrate an Optical Module containing an ultra-high dynamic range optical intensity modulator array with associated high speed drive circuitry. The Optical Module will be designed to fit in a VME-type rack card.