【作者】 段倩倩；

【导师】 周忠祥；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2009， 硕士

【摘要】 顺电相钽铌酸钾锂(KLTN)晶体是近年发展起来的性能优异的新型电控光折变材料。在相变温度附近电光效应显著,是目前发现的具有最大二次电光系数的晶体,通过外加电场可以显著提升其光折变效应。目前,尚未有基于二次电光效应的顺电相KLTN晶体简并四波混频相位共轭特性的报道。因此,对顺电相KLTN晶体相位共轭特性进行研究将促进电控相位共轭器件的发展,具有重要的应用价值。采用折射率椭球法描述了顺电相晶体中二次电光效应,讨论了顺电相晶体中的体相位光栅。由Maxwell方程出发,在泵浦光非耗尽和忽略吸收时,推导出顺电相晶体中基于二次电光效应的简并四波混频耦合波方程及其解,得到了其相位共轭反射率的表达式。并根据这个表达式,模拟了相位共轭反射率R随泵浦光强比q、外加电场E0和有效电光系数seff的变化规律。测量了KLTN晶体的基本物理性质,确定了其居里温度、透过性能及光激载流子类型。实验研究了温度、外加电场、写入光夹角等因素对顺电相KLTN晶体二波耦合衍射效率的影响。搭建了四波混频相位共轭光路,实现了电控相位共轭输出,得到了高达208%的相位共轭反射率。实验研究了相位共轭反射率随泵浦光与信号光光强比?、外加电场E0和温度T的变化规律。介绍了光学全息的基本原理,在KLTN晶体中实现了二波耦合全息的存储和再现和相位共轭图像全息再现。由实验结果可知,KLTN晶体具有良好的全息存储与再现性能。更多还原

【Abstract】 Paraelectric potassium lithium tantalate niobate (KLTN) crystal is a new voltage controlled photorefractive material with excellent performance in recent years. It has the largest quadratic electro-optic coefficient at present, and remarkable electro-optic effect near the phase transition temperature. It shows enhanced photorefractive effect under external electric field. To the best knowledge of the author, there is no report about four-wave mixing (FWM) phase-conjugation based on quadratic electro-optical effect of paraelectic KLTN crystal. Researching on four-wave mixing phase-conjugation of paraelectric crystal will promote the development of voltage controlled phase-conjugation device, and has important application value.Quadratic electro-optic effect of paraelectric crystal was described using index ellipsoid and volume phase grating of paraelectric crystal was discussed. From Maxwell equations, the coupled wave equations basing on quadratic electro-optical effect was obtained. According to the expression of phase-conjugation reflectivity, the dependences of phase-conjugation reflectivity changed with the ratio of pump intensity to signal intensity, external field and effective electro-optic coefficient were simulated.The Curie temperature, optical transmission properties and dominant charge carrier were determined. The influence of temperature, external field and two writing beams’s angle on two-wave coupling diffraction efficiency were measured. Voltage controlled phase-conjugation output was implemented, and high phase-conjugation reflectivity of 208% was achieved. The influence of the ratio of pump intensity to signal intensity, external field and temperature on phase-conjugation reflectivity was investigated.The basic principle of optical holography was described. The two-wave coupling storage and reconstruction and phase conjugation holography reconstruction of images were realized. The result indicates that paraelectic KLTN crystal has nice holographic storage and reconstruction capacity.更多还原