A Vanadium Doped ZnTe, A New Material For Real-Time Optical Signal Processing: Crystal Growth and Optical Characterization

This proposal deals with the growth of a relatively new class of photorefractive semiconductor, Vanadium Doped ZnTe, which has fast response at relatively low intensity and high sensitivity required for real-time applications. Brimrose Corporation, in collaboration with the Center for Photonic Technology at The University of Southern California and Hughes Research Laboratories, Malibu, California, has in recent years produced ZnTe:V crystals and reported photorefractivity in this material for the first time. Our preliminary study indicates that ZnTe is an outstanding photorefractive material with a sensitivity range expanding from 0.6um to beyond 1.3um. Available ferroelectric oxides and sillenites do not have required efficient response beyond visible wavelengths. Moreover, these classes of materials lack the sensitivity and speed of response necessary for real time applications at low laser power levels. Semiconductors such as GaAs and CdTe are demonstrated to have a sensitive and fast response; however, their energy band gaps limit their use to wavelengths longer than 0.9um. The large band gap III-V and II-V semiconductors such as GaP, CdS, and ZnTe have the potential for sensitive operation in the wavelength range of O.57um to 1.3um. A comparison of the figures of merit n3r/Er, corresponding to the electro-optic index change per separated charges suggests the highest sensitivity in ZnTe. The superior sensitivity of ZnTe with respect to other materials is now confirmed through our preliminary experimental findings. During Phase I, the major emphasis will be placed on the purification of the starting material, determination of optimum doping concentration of vanadium for operation in the wavelength range of 0.8um to 0.85um and the growth of photorefractive ZnTe Crystals. The crystals will be grown by Physical Vapor Transport (PVT) technique which has already been standardized at Brimrose. The major emphasis will be on the growth of large crystals (at least 6mm to 8mm3) with the diffraction efficiencies better than 3%. The crystals grown using PVT will be characterized with respect to crystallographic defects as well as electrical and photorefractive properties. Sam