Some aspects of fanning, self-focusing and self-defocusing in a photorefractive Ba0.77Ca0.23TiO3crystal

Abstract

We present some aspects of wave self-focusing and self-defocusing in a photorefractive Ba0.77Ca0.23TiO3 (BCT) crystal without external electric field and without background illumination. The effects depend on the cross-section of the input beam. We show that by decreasing the diameter of the input beam from 730 µm the fanning effect disappears at 150 µm. A symmetrical self-focusing is observed for input diameters from 150 µm down to 40 µm and a symmetrical self-defocusing for input diameters from 40 µm down to 20 µm. The 1D self-trapping is detected at 65 µm in BCT. Light intensity and wavelength are correspondingly 3 mW and 633 nm.