Polarization Characteristics of Bulk Ultrasonic Waves in Acousto-Optic Paratellurite Crystal

The paper examines the orientation of the acoustic polarization vector of bulk plane ultrasonic waves propagating along various directions relatively to the crystalline axes of tetragonal acousto-optic crystals. In particular, the strongly anisotropic tetragonal crystal tellurium dioxide (TeO₂) is considered in details in the paper. Theoretical analysis and numerical calculations confirm that in the tetragonal materials the transformation of a quasi-longitudinal wave into a quasi-shear acoustic wave takes place if the elastic coefficient c ₆₆ exceeds c ₁₁. The carried out theoretical analysis also determines the maximum angle at which this transformation of the ultrasonic waves takes place in the tetragonal materials. Furthermore the angular range of the directions in the paratellurite crystal in which quasi-longitudinal waves are transformed into quasi-shear waves is determined.