Gaussian beam phase change and deflection in Raman-Nath interaction

In this work there is presented a description of the Gaussian light beam diffraction on the planar ultrasound wave in the Raman-Nath region by the complex optical rays method. The case of the perpendicular light beam incidence (i.e. its axis relatively to the direction of propagation of the ultrasound beam fulfilled the acoustics buffer of Δz width was considered. Final analytical formulae gives a possibility analyze the influence of such parameters as: a size and position of the Gaussian beam waist, a laser-screen (detector) distance, a position of the ultrasound beam and Raman-Nath parameter value on diffraction pattern. It has been proved that in some cases the diffraction beams have a fine structure. The light beam deflection contribution to the diffraction pattern was taken into account. Obtained analytical formulas were illustrated by some graphs of the light intensity distributions in beams diffracted on ultrasound wave propagated in fused quartz.