CHARGE-TRANSPORT PARAMETERS OF PHOTOREFRACTIVE STRONTIUM-BARIUM NIOBATE CRYSTALS DOPED WITH CERIUM

A complete set of charge-transport parameters of photorefractive ceriu m-doped strontium-barium niobate crystals is determined: the concentra tions of filled and empty traps, the photon-absorption cross section, the quantum efficiency for excitation of an electron upon absorption o f a photon, the recombination coefficient, and the charge-carrier mobi lity. These parameters are obtained evaluating optical absorption, con ductivity, nonsteady-state photocurrents, neutron-activation analysis, and x-ray photoelectron spectra. The effective absorption radius of t he filled electron traps is small and the effective trapping radius is large compared with the ionic radii. Before recombination with deep l evels the excited electrons are trapped several times by shallow level s. A detailed description of the charge transport is obtained, and the properties of optimized crystals are deduced. (C) 1998 Optical Societ y of America.