Acceleration of a photorefractive response in Bi 12 TiO 20 crystals

Abstract

Significant acceleration of a photorefractive response has been obtained in a thin and long Bi<SUB>12</SUB>TiO<SUB>20</SUB> waveguide-like crystals using the nonlinear self-channeling of a laser beam. Total internal reflections of strong fanning beams and their coupling with the pump beam result in the light intensity redistribution inside the crystal and in the generation of the photorefractive surface wave of high intensity, which speeds up the photorefractive response by enhancing both the beam intensity and the interaction length. The exceptionally fast photorefractive response as well as its anomalous acceleration with the increasing amplitude of ac electric field applied to the crystal were experimentally demonstrated. The photorefractive surface wave can be used as the energy source for the amplification of weak signals in two-wave mixing experiments. This fact may lead to a fabrication of fast photorefractive devices operating with low power laser-diodes.