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Study on self pumped phase conjugation and four wave mixing in a BaTiO_3 photorefractive crystal.

BaTiO_3光折变晶体自泵浦相位共轭和四波混频研究

基本信息

批准号：
06650379
负责人：
MISHIMA Teruhito
金额：
$ 1.09万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06650379/
关键词：
Optical phase conjugation Self-pumped phase conjugation Four wave mixing Photorefractive crystal Response time BaTiO_3 crystal Self-pumped four wave mixing

项目摘要

The location and profile of phase conjugate image produced by Gaussian beam pumped DFWM are studied. The equation describing the dependence of the conjugate image location and the transverse magnification factor on the gaussian beam parameters are derived. The reconstructed images of distorted probe object are calculated numericallyand it is found that the quality of the image is limited by the curvature, as well as, by the spot size of the Gaussian pump beams.Ordinary Self-Pumped Phase Conjugator (SPPCM) is demonstrated with use of a BaTiO_3 photorefractive crystal and analyzed. The comparison between the experiment and the theoretical analysis makes it possible to control the reflectivity of the SPPCM.Self-Pumped Four Wave Mixing (SPFWM) in a single BaTiO_3 crystal is demonstrated, which means that a simple phase conjugator with two incident beams is realized. At first, the conjugator was unstable and it is found that refractive index gratings were produced at a same region in the crystal and they sompete with each other. The competition is the origin of unstableness, so that separating the two index gratings leads to stable operation of SPFWN.The reflectivity and the response time of SPFWM are measured and found that it is as fast as ordinary four wave mixing and is faster than SPPCM by the order of two.As a result of this study, SPFWM in a BaTiO_3 crystal which uses phase conjugate beam as one of the pump beams which is generated by SPPCM in the same crystal is realized with rather simple optical system. It is found that the response of the SPFWM is as fast as ordinary four wave mixing.

研究了高斯光束抽运DFWM产生的相位共轭像的位置和形状。导出了描述共轭像位置和横向放大因子与高斯光束参数关系的方程。数值计算了畸变探测物的再现像，发现再现像的质量不仅受高斯泵浦光的光斑尺寸的限制，而且还受曲率的限制，并利用BaTiO_3光折变晶体演示了普通自泵浦相位共轭器（SPPCM），并对SPPCM进行了分析。实验结果与理论分析的比较表明，SPPCM的反射率是可控的。在BaTiO_3单晶中实现了自泵浦四波混频（SPFWM），即实现了一个简单的双光束相位共轭器。首先，共轭器是不稳定的，发现折射率光栅在晶体的同一区域产生，它们相互作用。这种竞争是不稳定性的根源，因此，将两个折射率光栅分开，可以使SPFWN稳定工作.测量了SPFWM的反射率和响应时间，发现它与普通四波混频一样快，比SPPCM快二个数量级.作为研究结果，利用BaTiO_3晶体中SPPCM产生的相位共轭光作为泵浦光，用简单的光学系统实现了晶体中的SPFWM。实验结果表明，该结构的响应速度与普通四波混频结构相当。