Optical and photorefractive properties of Nb-doped BaTiO3

The photorefractive properties of BaTiO3 are gradually modified by the addition of Nb which change the charge carrier from hole to electron. Before the compensation point, the dark conductivity decreases and the response time increases with increasing Nb concentration. Two beam coupling gain can be explained by using the deep and shallow trap model with hole as the major carrier. Near the compensation point, the deep and shallow trap model is needed, in addition to the electron-hole competition to explain this. After the compensation point, an absorption around 600 nm evolves, the dark conductivity increases very fast, and the electron becomes the major carrier. (C) 1999 American Institute of Physics. [S0021-8979(99)03104-7].