Acoustic diffraction of light in anisotropic media

The Bragg formalism which describes the diffraction of optical radiation by traveling acoustic waves is generalized to include diffraction in anisotropic media. When the diffracted and incident optical polarizations are different, the Bragg relations require important modification. The correctness of the suggested modifications is confirmed by experiments using optical diffraction from longitudinal and transverse acoustic waves in crystal quartz and in sapphire. A special case of diffraction from longitudinal waves in an anisotropic medium is discussed as a simple example of a collinear parametric interaction.