Photoconductivity of photorefractive Sr0.61Ba0.39Nb2O6:Ce crystals at high light intensities

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Abstract
A method is presented to perform direct photoconductivitymeasurements of Sr0.61Ba0.39Nb2O6:Ce crystals at high intensities: A high voltage is applied to the sample and subsequent illumination yields a photocurrent through the crystal which charges a capacitor. Finally an electrometermeasures the voltage of this capacitor. From voltage, capacity and exposure time the photoconductivity is calculated. Measurements with light pulses of a Q‐switched frequency‐doubled Nd:YAG laser (pulse duration 20 ns, light wavelength 532 nm) are performed. The photoconductivity σph increases sublinearly with light intensity I according to σph∝I x with x<1. The experimental results point to Ce3+/4+ as the dominant photo‐ refractive center in Sr0.61Ba0.39Nb2O6:Ce at high intensities.