DEFECT PROPERTIES AND THE PHOTOREFRACTIVE EFFECT IN BARIUM-TITANATE

Barium titanate (BaTiO3) is a photorefractive material that exhibits high gain. However, significant improvements in performance can be achieved through proper control of defect properties. Our approach to optimizing these properties involves growth of pure and doped BaTiO3 crystals. Annealing under controlled atmospheres is used to control the valence state of the dopants. The effects of growth conditions on the defect and photorefractive properties are characterized by optical absorption, electron paramagnetic resonance, and two-beam coupling measurements. Theoretical modeling of defect equilibria aids in understanding the relation between processing conditions and photorefractive behavior. Substantial differences in behavior are observed for various dopants and annealing conditions. Thus far, cobalt-doped crystals are the most promising for visible and near-infrared applications.