Abstract

Light-induced grating erasure, beam coupling, and photoinduced absorption experiments on pure and iron-doped samples of BaTiO₃ were performed. These measurements were made over a wide range of intensities, and it was found that the effective trap density, mobility-lifetime product, photoinduced absorption, and photoconductivity all displayed a nonlinear intensity dependence. Our data semiquantitatively fits a model based on the work of Bube¹ in which there is a distribution of trapping centers within the band gap. However, in contrast to the assumptions of Bube, it appears that the photoionization and recombination rates of these centers also vary with trap depth. The model assumes that illuminating the crystal results in (1) an increase in the density of filled trapping states above the dark Fermi level and thus an increase in the absorption, (2) an increase in the density of ionized deep centers which results in both a decrease in the recombination time and an increase in the effective trap density, and (3) essentially no change in the mobility since this is dominated by shallow trapping states. It is shown that the photoinduced absorption correction appropriate for beam coupling measurements is more complicated than the addition of a constant term to the background absorption.²

© 1988 Optical Society of America