Decai Ma

Growth and photorefractive properties of an Fe-doped near-stoichiometric LiNbO3 crystal

A near-stoichiometric LiNbO3 crystal with 0.02 wt% Fe2O3 doping was grown from a Li-rich melt (Li/Nb = 1.38, atomic ratio) by the Czochralski method in air atmosphere. The OH− absorption band was characterized by infrared transmittance spectra. The appearance of the 3466 cm−1 absorption band (2.89 µm) manifests that the composition of the grown crystal is close to the stoichiometric ratio. The photorefractive properties were measured by a two-wave coupling experiment. The measured results show that the Fe-doped near-stoichiometric LiNbO3 crystal has a larger exponential gain coefficient than the Fe-doped congruent LiNbO3 crystal. The remarkable gain can be attributed to the photovoltaic field being comparable with the effective limiting space-charge field.

INFLUENCE OF POST-TREATMENT ON OPTICAL PROPERTIES OF Sc:Ce:Cu:LiNbO3 CRYSTALS

The congruent Sc(3 mol%):Ce:Cu:LiNbO3 single crystals were grown by the Czochralski method and three kinds of different samples were prepared by proper reduction or oxidation post-treatment processes. The extrinsic defect structures of samples were determined by infrared transmittance spectra. Two-wave coupling and light induced scattering experiments were used to measure the photorefractive properties. It is found that the reduction treatment made erasure time and diffraction efficiency decrease, but light-induced scattering resistance increase; the inverse case occurred with oxidation treatment. Analysis indicated that photoconductivity change was responsible for photorefractive properties.

Investigation of structure and optical properties of Nd, Zn double-doped LiNbO3 crystals

A serial of Nd, Zn double-doped LiNbO3 crystals were grown. The dependence of structure on the concentration of ZnO was investigated on the basis of analysis of UV-visible absorption spectra and IR transmittance. In addition, the photoconductivity and the loss of signal-to-noise-ratio coefficient of these as-grown crystals were also measured in terms of two wave coupling. Finally, one of Nd, Zn:LiNbO3 crystals was applied to holographic associative memory system, and excellent output performance was gotten. The results indicate that Zn doping with various concentration in Nd:LiNbO3 crystal change the defect structure, especially increase the photoconductivity, and therefore efficiently suppress the noise generation.