MULTIPLE GRATINGS IN SEMIINSULATING GAAS CRYSTAL

Abstract

Analyzing anisotropic diffraction properties of photorefractive gratings in GaAs crystals and the symmetry difference of energy exchange between index-of-refraction and amplitude gratings, we identify three different kind of gratings, namely a photorefractive, a non-photorefractive index-of-refraction and a photochromic grating simultaneously occurring in semiinsulating GaAs crystals. We show that the latter two gratings probably originate from electric polarizability changes arising from spatial modulation of photoelectron traps occurring during photorefractive recording. Experiments are carried out using a continuous phase modulation technique in a two-wave mixing setup at a wavelength of 1.06 mu m.