Isotropic diffraction of a light beam by acoustic waves of fundamental frequency and harmonics

A set of equations describing acoustooptic diffraction of a light beam by acoustic waves of a fundamental frequency and its harmonics in an isotropic medium is obtained. The possibility of suppressing higher diffraction orders by adding the second or third harmonic to the fundamental monochromatic acoustic signal is theoretically justified. It is demonstrated that the maximum degree of suppression decreases with an increase in the light beam divergence. Results of simulation are presented for some particular cases of diffraction.