Bragg coupling efficiency for guided acoustooptic interaction in GaAs

The guided acoustooptical interaction on the (100) plane of GaAs is investigated as a function of waveguide thickness type of mode, acoustic frequency, direction of acoustic wave propagation, and substrate refractive index Our calculated results indicate that best efficiency is obtained for TE(0) ? TE(0) optical modes and for acoustic surface wave propagating along the ?01l? direction at a waveguide thickness close to cut-off Under these conditions, approximately 75 mW of acoustic power is required for 100% diffraction. For a transducer aperture giving 50 Omega of radiation resistance, the rf bandwidth of the diffraction is limited essentially by the frequency bandwidth of the interdigital transducer. A comparison of the calculated results with experimental data at 1.06-microm optical wavelength is also given.