Investigation On Optical Properties In Biased Photorefractive Crystals

External applied field has a profound influnce on macro-optical properties of photorefractive(PR) crystals and people have done a lot to study, including the external applied field on diffraction efficiency, the external applied field on light induced scattering and the external applied field on coupling characteristics of light and so on. In this paper, part of the optical properties were investigated by theory and experiments in biased PR CSBN (Ca0.28Ba0.72)x(Sr0.60Ba0.40)1-xNb2O6)) and Ce:SBN crystals, which including conoscopic interference, the shape of light beam under the external applied field and translational characteristics of quasi-steady optical solitons and so on. The main research contents are as following:Based on the conoscopic interference in negative uniaxial crystals and the linear electro-optic effect of CSBN crystals, the properties of conoscopic interference in biased CSBN crystals and formulas of the linear electro-optic coefficientsγ33 andγ13 were studied and deduced in this paper. And then, an experimental method for measuring the linear electro-optic coefficients of CSBN crystals was proposed. According to this, an experimental platform was designed to measure the linear electro-optic coefficientsγ33 andγ13 of the crystal CSBN50. The results are:γ33= (141.0±0.5)×10-12m/V,γ13=(85.0±0.5)×10-12 m/V.Light beam self-focusing and self-defocusing process in biased Ce:SBN crystals were studied. In the case, the change of transported beam under the external applied field was observed while changing the strength and direction of the external applied field, and then its forming mechanism and the rule were analyzed. In the beam self-defocusing experiment, this paper majorly reports the evolution of self-defocusing to 'dark trace';Moreover, the quasi-steady bright spatial solitons had been observed in biased Ce:SBN crystals.On the basis of the experiment of the quasi-steady-state photorefractive spatial solitons, this paper improved the experimental device;a crystal translation device was added to achieve the crystal translation when the quasi-steady-state photorefractive spatial soliton is forming. The translation characteristics of quasi-steady bright spatial solitons in biased crystals were studied. In the case of crystal translation, the existence time of quasi-steady-state photorefractive spatial solitons is greatly extended. With the crystal translation, optical soliton will be deflected, just as a parabola. The direction of soliton bending relates to the translation of the crystal. These phenomena and the influence of diffusion effect on spatial solitons is very similar. The point of this paper thinks translation operation is a perturbation process, which causing a soliton deflection.