Two-dimensional image edge enhancement by two-phonon Bragg diffraction

A model of acousto-optic interaction is developed for describing two-phonon Bragg diffraction in a gyrotropic single TeO₂ crystal, which makes allowance for ellipticity of crystal optical eigenwaves. Formation of a two-dimensional edge of an image in the first diffraction order is explained by invoking a three-dimensional description for the wave surfaces of optical eigenwaves.