Extraordinary Variants of Anisotropic Acousto-Optic Interaction in Optically Biaxial Crystals

Using as an example rhombic crystal Tl3AsS4, we investigated unusual variants of acousto-optic scattering of light that occur when interacting beams propagate near one of the optical axes of a biaxial crystal. The main attention is paid to the peculiarities of frequency dependences of Bragg angles for different directions of acoustic wave propagation. A number of unusual regularities of the acousto-optic effect in biaxial crystals have been established, which may have practical significance. In particular, it is shown that a non-polarized radiation modulator can be implemented on the basis of Tl3AsS4 crystal, which significantly exceeds the existing serial analogues in its characteristics.