THEORETICAL-STUDY OF FE DOPING AND OXIDATION-REDUCTION INFLUENCE ON THE PHOTOREFRACTIVE EFFECT IN BATIO3

We numerically solve charge-transport and Poisson equations for photorefractive BaTiO3 single crystals with a band model, using four impurity levels, Fe2+-Fe3+, Fe3+-Fe4+, V(o)..-V(o)., and V(o).-V(o)x. Densities and photoinduced spatial distributions of each population are computed as a function of annealing O partial pressure. Space-charge field and beam-coupling gain are also computed as a function of annealing O partial pressure, temperature, Fe concentration, grating wave vector, and light intensity. We discuss the intervening mechanism of impurity centers and the correlations between experimental conditions of crystal growth, oxidation-reduction treatments, and measurement parameters.