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 emerge in photorefractive crystals even in the absence of an applied electric field if the recording pattern is oscilliating in a definite law. We 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 is a linear coordinate, t is time, and m, k, omega, and phi are constants). In this case the dc component is j0 approximately -sin phi. One can detect the relative phases of the harmonics by this means.