Close to collinear acousto-optical interaction in paratellurite

First results on the investigation of close to collinear acousto-optical interaction in paratellurite single crystals are presented. Anisotropic Bragg diffraction of light on ultrasound in TeO₂ with a length of interaction of up to several centimeters is examined. A peculiarity of the interaction is optical beam propagation in the crystal collinearly with group velocity of ultrasound. It is shown and verified experimentally that the interaction is characterized by an extremely high selectivity of scattering. Some applications of the examined regime of diffraction are discussed.