We demonstrate a method of simultaneous holographic recording and readout in photorefractive crystals that provides high write-read beam isolation and wide angular bandwidth. The method uses orthogonally polarized read and write beams and parallel tangent diffraction geometry near the equal curvature condition to provide spatially separable, orthogonally polarized diffracted output beams with high isolation and wide Bragg-matched angular bandwidth. The available angular bandwidth of this read-write technique is analyzed, simulated, and experimentally investigated. The measured angular bandwidth internal to the crystal is approximately 18° × 6° for our 45°-cut BaTiO(3) crystal, yet the entire hologram still demonstrates high Bragg selectivity. In contrast, traditional nonparallel-tangent geometries yield angular apertures of the order of 1° × 4°.
We present an overview of continuing research on a dynamic optical system for producing variable delays of radio frequency (RF) signals. Our approach utilizes both a 16 & 64 tap programmable delay line. The approach uses a micro-laser diode array to tap an acousto-optic (AO) cell at various spatial positions along the acoustic channel. This generates multiple delayed versions of the input signal to the AO cell. The use of the laser diode array allows for a programmable time delay, programmable weighting of each delay, a large number of delays equal to the number of elements in the diode array, and multiple delays at one time. This architecture, upon completion of future compatibility testing will replace an existing multi AO cell tap delay line as part of an adaptive optical processor for side lobe jamming cancellation.
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