ACOUSTIC BEAM STEERING BY AN INTERDIGITAL TRANSDUCER FOR WIDEBAND BULK WAVE ACOUSTOOPTIC DEFLECTORS.

An interdigital transducer method has been exploited for generating and steering the acoustic beam on a LiNbO//3 bulk wave acoustooptic Bragg cell. The interdigital transducer, deposited on the x surface of a LiNbO//3 crystal, is effective in generating longitudinal waves with the wave vector lying in the xz plane. The acoustic radiation pattern consists of two main lobes whose directions depend on the acoustic frequency and axis. The acoustooptic interaction geometry is such that one of the steered acoustic beams tracks the Bragg angle and reduces the momentum mismatch over a wide range of frequencies. Results are reported for two LiNbO//3 cells operating in the frequency range 1. 4-2. 1 GHz and 1. 05-2. 0 GHz, with a diffraction efficiency of approximately 2% per watt of acoustic power.