Simple methods of measuring the net photorefractive phase shift and coupling constant

We report measurements of the photorefractive phase shift and coupling constant of several photorefractive materials. We solve the problem of beam coupling and diffraction in a material with a dynamically written grating for arbitrary input beams. These solutions are used to determine the beam coupling as a function of the photorefractive phase ø and coupling constant g when one beam is either sinusoidally phase modulated or ramped in phase. Experimental results are obtained for LiNbO(3), BaTiO(3), and for paraelectric potassium lithium tantalate niobate as a function of applied electric field.