MECHANISM OF LOCK-IN DETECTION WITH THE A ID OF AN ALTERNATING-FIELD PERPENDICULAR TO THE SURFACE OF A PLANAR PHOTOREFRACTIVE WAVE-GUIDE

An analysis is made of the mechanism of formation of a stationary grat ing in a planar photorefractive waveguide by a travelling interference pattern with the aid of an alternating electric field applied perpend icular to the waveguide layer. A theoretical calculation is reported o f the distribution of the space-charge field in a transverse section o f the waveguide. Finite drift lengths and trap saturation are taken in to account in these calculations, which are carried out on the assumpt ion of a weak contrast in the interference pattern.