Dark decay behaviours of photorefractive grating induced by two deep-trap levels in Ce:BaTiO₃

Dark decay behaviors of photorefractive grating in Ce:BaTiO₃ crystal are studied experimentally. It is observed that two deep-trap levels, i.e. Fe-ion deep level and Ce-ion deep level, both participate in the photorefractive process. A simplified two-deep model is presented based on the one-deep trap model and the shallow-deep trap model, with which we analyze quantitatively the contribution of each deep level to the whole space-electric field and thus the photorefractive grating varying with the different grating wave vectors and different writing intensities.