Influence of Acoustic Anisotropy on Frequency Bandwidths of Bragg Diffraction in Two Orthogonally Polarized Diffraction Orders

This paper theoretically and experimentally examines a specific regime of acousto-optic diffraction during which an arbitrarily polarized incident light in a paratellurite crystal is scattered simultaneously into two orthogonally polarized diffraction maxima. We examined acoustic energy walk-off in the crystal and its influence on phase matching as well as on distribution of light energy between the two diffraction orders. This influence was theoretically considered by means of wave vector diagrams illustrating momentum conservation law during the photon phonon interaction. We obtained expressions for mismatch parameters in the ordinary +1 and extraordinary 1 diffraction orders both depending on the walk-off angle. The obtained parameters were used in the Raman Nath system of coupled-wave equations to calculate the diffracted light intensities and frequency bandwidths of diffraction. We measured the bandwidths in experiments carried out in the (110) plane of paratellurite crystal at the walk-off angle equal to 54 degrees