Cascading processes in the nonlinear diffraction of light by standing acoustic waves

Abstract

International audienceThe contribution of two types of cascading process to the nonlinear optical diffraction of electromagneticwaves from a standing acoustic wave in a GaAs crystal is theoretically studied. The first type of cascadingprocess results from second-harmonic generation followed by linear acousto-optical diffraction, while the secondtype involves linear acousto-optical diffraction from the standing acoustic wave and subsequent sum-frequencygeneration. In contrast to the third, direct, nonlinear acousto-optical diffraction processwe previously investigated,the photoelastic interaction between electromagnetic and acoustic waves is here linear. We establish the rulesgoverning the cascading processes and show that in most cases the output signal simultaneously results from twoor even three of the possible nonlinear diffraction mechanisms. However, we demonstrate that a careful choice ofthe incidence angles of the incoming electromagnetic waves, of the polarization combinations of the incomingand diffracted waves, and of the type of acoustic wave (longitudinal or transverse) makes it always possible todistinguish between the direct and either of the two cascading processes