Abstract

Vanadium-doped cadmium telluride ingots were grown by the vertical Bridgman-Stockbarger method. After shaping, one sample was annealed under cadmium atmosphere. Picosecond four-wave mixing (FWM) on free carrier and photorefractive optical nonlinearities allowed us to characterize deep-impurity related carrier generation at 1.064 µm, transport and recombination mechanisms as well as space charge filed transients. All samples have shown strong photorefractive response and typical saturation of SC field with excitation. Temporal and exposure characteristics of FWM revealed the presence of some defect-related deep centers which have been transformed by annealing: the reduced electrical activity of deep centers resulted in slower recombination rate and faster diffusion while strength of the SC field remained nearly the same. Moreover, the relaxation times of both free carrier and photorefractive nonlinearities became significantly longer, and the later revealed contribution of pieziolectricity on the photorefarctive effect. These results point to a significant improvement of photorefractive quality of the crystals by annealing and potential of FWM techniques for its monitoring.

© 2005 Optical Society of America