Spatial coherence property of a laser beam during acousto-optic diffraction

The spatial coherence property of a partially coherent light during the Bragg acousto-optic interaction is investigated. Starting from the wave equation, four coupled, parabolic equations that can describe the evolution and the propagation of mutual intensity functions of the diffracted light during the acousto-optic interaction are derived. A partially coherent light beam with arbitrary spatial profile and complex degree of spatial coherence is assumed to be incident on the Bragg acousto-optic cell. With the use of a statistical theory of linear systems, a general formalism of angular-correlation functions for zero-order and minus-one-order light can be derived. The corresponding mutual intensity and complex coherence factor functions are hence implemented numerically. From the solutions one can note that, through the acousto-optic interaction, the degrees of spatial coherence of the diffracted light beams are controllable by the intensity and the frequency of the sound wave.