INITIALIZATION OF THE HOLOGRAPHIC CURRENT CONSTANT COMPONENT BY RECORDING PATTERN OSCILLATION IN PHOTOREFRACTIVE CRYSTALS

We show that a constant component of the holographic current may emerg e in photorefractive crystals even in the absence of an applied electr ic field if the recording pattern is oscilliating in a definite law. W e derive conditions on the oscillations for the effect to appear. For instance, a fringe pattern with an intensity I approximately 1 + m cos [kx + DELTA cos omegat + delta cos(2omegat + phi)] is fitted (here x i s a linear coordinate, t is time, and m, k, omega, and phi are constan ts). In this case the dc component is j0 approximately -sin phi. One c an detect the relative phases of the harmonics by this means.