Studies of impurity levels in Rh-doped and Ce-doped photorefractive BaTiO3

Impurity levels, light-induced and thermo-induced charge transfer processes in Rh-doped and Ce-doped photorefractive BaTiO3 were studied. The thermal depths and optical transitions of these impurity levels in the crystals wer e determined by using such methods as light-induced absorption, thermo-indu ced absorption, and grating dark decay. The origins of these impurity level s were discussed. We demonstrated, for the first time to our knowledge, tha t thermoinduced absorption spectroscopy is a useful and complementary techn ique for investigating the impurity levels in photorefractive crystals. Wit h this technique, the deep impurity level generated by Ce in BaTiO3:Ce was revealed and identified.