INTENSITY-DEPENDENT ABSORPTION AND PHOTOREFRACTIVE PROPERTIES IN CERIUM-DOPED BATIO3 CRYSTALS

We report the optical absorption and photorefractive properties of a s eries of cerium-doped barium titanate crystals. The light-induced abso rption and the intensity-dependent two-beam coupling gain coefficient indicate that there are at least two active trap levels in cerium-dope d BaTiO3 crystals. The total effective trap density, the Debye screeni ng wave vector, and the intensity-dependent factor increase with ceriu m-doping concentration as well as the pump beam intensity. The positiv e tight-induced absorption and the negative absorption gain coefficien t as the grating wave vector approaches zero indicate that the excitat ion cross section of shallow traps is larger than that of deep traps. One of these crystals exhibits a two-beam coupling coefficient of 8.06 cm(-1) for ordinarily polarized beams, which is the highest ever repo rted to date. Both electro-optic index grating and absorption grating are contributing to the coupling coefficient. The response time of as- grown cerium-doped BaTiO3 with 15 ppm cerium is 220 ms at an intensity of 800 mW/cm(2). (C) 1995 American Institute of Physics.