Bragg shift for reflection-type photorefractive holographic gratings

The steady-state differential equations of two waves coupling in photorefractive materials for reflection geometry have been numerically solved, and the Bragg-shift are calculated for a range of the coupling intensity and the phase shift. By means of a quasi-steady state approximation, the Bragg-shift as a function of the coupling intensity has been found, and hence as a function of the recording time. There is a good agreement between experimental measurements and numerical calculation.