Abstract

When coherent optical beams cross in a photorefractive crystal such as BaTiO₃, SBN, there is an automatic 90° phase shift between beams A and B at the place of maximum refractive index of the photorefractive grating, because there is a 90° phase shift between the grating and the interference pattern of two beams A, B (A, B also indicate the amplitude of beams A, B). Because of the energy conservation law there is a 90° phase difference between A_t and A_d, B_t and B_d (beams A and B will be divided into transmitted beam A_t, B_t and diffractive beam A_d, B_d, respectively).

© 1989 Optical Society of America