Measurement of the photorefractive phase shift by polarization interferometry

Abstract

We present a new approach to measure the phase shift between the photorefractive grating and the interference pattern in two-wave-mixing experiments. This approach is based on using two polarizations for one of the input beams and making them interfere after propagation through the crystal. The real and imaginary parts of the exponential gain are determined independently during grating buildup and erasure. Active stabilization of the optical paths based on this technique is also described and is shown to provide optimal grating formation. The method is applied to an undoped BaTiO3 crystal in which the contribution of traps grating is found negligible.