Сoupled-Mode Equations for the Acousto-Optic Diffraction of a Divergent Beam in an Absorbing Medium

Acousto-optic (AO) interaction in optically isotropic media is studied. Vector differential equations are obtained that describe the Raman–Nath diffraction of light on ultrasound in an absorbing medium. Particular emphasis is placed upon light-beam divergency caused by its transverse restriction.