Harmonic modulation of light by means of collinear acousto-optic interaction

The collinear anisotropic interaction of light with a standing acoustic wave generated in a lithium niobate crystal is discussed. Diffraction may be applied for harmonic modulation of laser light. The analysis of the light modulation is based on the concept of vector diagrams. A set of differential equations is derived to describe up to five interacting optic waves in the material. It is shown that solution of the equations by the method of successive approximations yields amplitudes of electric fields corresponding to diffracted and transmitted optical beams at the output of the crystal. Dependences of the amplitudes of the interacting waves on the acoustic frequency and length of the acousto-optic interaction are also discussed.