Abstract

We experimentally determined materials parameters in photorefractive barium titanate using a Raman-Nath probe technique of laser induced dynamic gratings. In this technique, shown in Fig.1, coherent co-planar writing beams (wavelength λ_w) propagating in the X-Y plane intersect inside the crystal and form an interference pattern, inducing refractive index grating planes via the photorefractive effect. A probe beam (wavelength λ_p) propagating in the Z-direction passes through and parallel to the grating planes and is diffracted. The resulting diffraction pattern on a screen which is parallel to the X-Y plane and located beyond the crystal consists of a set of discrete intensity maxima (modes) which are symmetrically located about the m=0 (undiffracted) order. The angle of diffraction, θ_Dm, of a particular mode, m, (where m=0, 1, 2, 3,…, integer) is a function of the ratio of the probe beam wavelength to the grating spacing in the crystal. The grating spacing, Λ_G, in the crystal is a function of the ratio of writing beam wavelength to intersection angle of the write beams in the crystal.

© 1987 Optical Society of America