NEARLY DEGENERATE 2-BEAM COUPLING IN PHOTOREFRACTIVE CRYSTALS WITH 2 SPECIES OF MOVABLE CARRIERS

Two-beam intensity coupling is calculated for photorefractive crystals with two types of movable charge carrier in the undepleted-pump appro ximation. The analytical expressions are derived for the temporal evol ution of the space-charge field; for weak coupling they are used for c alculation of the transmitted beam intensities. The results of the cal culation are compared with the experimental observations in photorefra ctive tin hypothiodiphosphate (Sn2P2S6). All experimental data are in reasonable quantitative agreement with the calculations. (C) 1998 Opti cal Society of America.