Light-induced absorption in photorefractive strontium barium niobate

Sr(0.59)Ba(0.41)Nb(2)O(6) and Sr(0.75)Ba(0.25)Nb(2)O(6) exhibit an intensity-dependent absorption in the visible spectral range. We perform pump (green)-probe (red) measurements and find variation as high as 0.45 cm(-1) in the absorption coefficient, which depends significantly on the polarization of the probe light beam. Our results indicate a nonexponential dark decay time of the induced absorption and suggest that the trapping potential of the shallow traps varies significantly from one trap to another (multiple isolated shallow traps).