PHOTOCONDUCTIVITY OF PHOTOREFRACTIVE SR0.61BA0.39NB2O6-CE CRYSTALS ATHIGH LIGHT INTENSITIES

A method is presented to perform direct photoconductivity measurements of Sr0.61Ba0.39Nb2O6:Ce crystals at high intensities: A high voltage is applied to the sample and subsequent illumination yields a photocur rent through the crystal which charges a capacitor. Finally an electro meter measures the voltage of this capacitor. From voltage, capacity a nd exposure time the photoconductivity is calculated. Measurements wit h light pulses of a Q-switched frequency-doubled Nd:YAG laser (pulse d uration 20 ns, light wavelength 532 nm) are performed. The photoconduc tivity sigma(ph) increases sublinearly with light intensity I accordin g to sigma(ph) proportional to I-x with x<1. The experimental results point to Ce-3+/4+ as the dominant photorefractive center in Sr0.61Ba0. 39Nb2O6:Ce at high intensities. (C) 1996 American Institute of Physics .