LIGHT-INDUCED ABSORPTION IN PHOTOREFRACTIVE STRONTIUM BARIUM NIOBATE

Sr0.59Ba0.41Nb2O6 and Sr0.75Ba0.25Nb2O6 exhibit an intensity-dependent absorption in the visible spectral range. We perform pump (green)-pro be (red) measurements and find variation as high as 0.45 cm-1 in the a bsorption coefficient, which depends significantly on the polarization of the probe light beam. Our results indicate a nonexponential dark d ecay time of the induced absorption and suggest that the trapping pote ntial of the shallow traps varies significantly from one trap to anoth er (multiple isolated shallow traps).