Defect structure and photorefractive properties of In:Eu:Fe:LiNbO3 Crystals with various Li/Nb ratios

In: Eu: Fe: LiNbO3 crystals were grown by the Czochralski technique with various ratios of Li/Nb =0.946, 1.051, 1.200, 1.382 in the melt. The crystal composition and defect structure were analyzed by the UV-visible and IR spectroscopy and X-ray diffration. The results showed that increasing the Li/Nb ratio can decrease the In3+ doping threshold concentration of In: Eu: Fe: LiNbO3 crystals. In two-wave coupling experiments, the writing and erasure time constants, maximum diffraction efficiency, photorefractive sensitivity, photoconduction, photovoltaic field and space-charge field of the crystals were measured and calculated. The dependence of the photorefractive properties on the defect structure of In: Eu: Fe: LiNbO3 crystals were discussed.