Acoustooptic interactions in the presence of diffraction for optical beams with arbitrary profiles

Abstract

Starting from the coupled wave equations describing acoustooptic (AO) interactions in the presence of propagational diffraction, a Fourier transform technique is used to express the interactions in the spatial frequency domain. The method used is identical to the technique for solving the paraxial wave equation to derive the transfer function of propagation and, hence, the Fresnel diffraction formula during free-space propagation of a light beam in the presence of diffraction. The coupled interaction equations in the spatial frequency domain clearly bring out the effect of propagational diffraction of the various scattered orders on the interaction process. To check the formulation, Bragg diffraction of a Gaussian light beam is considered. Results indicate, among other things, a shift in the expected centers of the zeroth-order and the first-order light beams. Detailed numerical simulations, comprising Fourier transforming the input beam profile to calculate the spectra of the scattered beams and hence, their profile in space using the inverse transform, are also presented.