MEASUREMENT OF THE SPATIAL PHASE-SHIFT IN HIGH-GAIN PHOTOREFRACTIVE MATERIALS

The correct determination of the spatial phase shift phi(p) in photore fractive materials is crucial to the proper characterization of novel materials. It is shown that the grating translation techniques commonl y used for the measurement of phi(p) need to be reevaluated for high-g ain materials. Strong energy and phase coupling leads to nonuniform sl anted gratings, which result in an apparent dependence of the phase sh ift of the beam ratio and the optical polarization. A revised theory i s presented, and analytical solutions are obtained for the special cas e of phi(p) congruent to pi/2. Numerical solutions for arbitrary phi(p ) are in good agreement with measurements in a photorefactive polymer. (C) 1997 Optical Society of America.