Measurement of Spatial Phase-Shift in High Gain Photorefractive Materials

A. Grunnet-Jepsen, C. L. Thompson, and W. E. Moerner

The correct determination of the spatial phase-shift, f_p, in photorefractive materials is crucial to the proper characterization of novel materials. It is shown that the grating translation techniques commonly used for the measurement of f_p need to be reevaluated for high gain materials. Strong energy- and phase-coupling lead to non-uniform slanted gratings which result in an apparent dependence of the phase shift on the beam ratio and optical polarization. A revised theory is presented and analytical solutions are obtained for the special case of f_p@p/2. Numerical solutions for arbitrary f_pare in good agreement with measurements in a photorefractive polymer.