We describe an acousto-optic interaction geometry in a uniaxial crystal which uses acoustic beam steering to couple incident and diffracted optical beams with parallel group velocities. The device uses tangential acoustic beam steering to provide large RF bandwidths at high efficiency. As with the acoustooptic tunable filter, the choice of parallel optic group velocities provides for a large input angular aperture, useful in multiplicative optical processing architectures. The parallel optical group velocities and beam steering geometry allow use of the Bragg cell with optical beams propagating in close proximity to the transducer, eliminating the dead time which is crucial in correlation cancelation feedback optical processors. The wide angular aperture allows this same interaction geometry to be used for high-efficiency wide- band acoustooptic modulators as well.
Robert T. Weverka,
Kelvin H. Wagner,
"Wide-angular aperture acousto-optic Bragg cell", Proc. SPIE 1562, Devices for Optical Processing, (1 December 1991); doi: 10.1117/12.50771; https://doi.org/10.1117/12.50771