【作者】 尚野；

【导师】 侯春风；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2009， 硕士

【摘要】 向列相液晶是一种高性能的非线性光折变材料,而且通过掺杂染料可使其性能大为改良。由于向列相液晶大的非线性系数,使得利用向列相液晶产生光学相位共轭波称为可能。从19世纪80年代起,已经有很多学者在这种材料中进行了光学相位共轭实验。本论文主要用简并四波混频的方法产生光学相位共轭波,对掺杂甲基红(MR)和掺杂C60的向列相液晶E7中的光学相位共轭特性进行了理论与实验的研究。我们利用向列相液晶中在相干光入射下形成的折射率光栅结合麦克斯韦方程组,参考相关文献推导了向列相液晶中四束光相互作用的四波耦合方程。并依据材料吸收系数的大小求得了方程的解析结果和数值结果,分别适合对不同样品的分析。我们制作了实验所需的E7+1%MR和E7+0.5%C60液晶盒,从理论上定性分析了两种样品各自的取向光折变的特点。搭建了用来产生光学相位共轭光的简并四波混频光路,测量了样品的基本光学特性,对两种样品都成功观察到了光学相位共轭波的产生。对不同实验条件下产生的相位共轭波进行了测量,得到了最佳的实验条件包括:样品厚度、入射光夹角、入射光偏振态等。在确定以上实验条件的前提下,两种样品在入射光强影响下的光学相位共轭波的变化和响应时间特性被详细测量。发现相位共轭光随入射光功率的变化存在饱和效应,并且E7+1%MR样品中形成了永久光栅,E7+0.5%C60样品中形成了瞬时光栅。另外还详细的研究了E7+0.5%C60样品的外加电压特性,得到了产生相位共轭光的阈值电压和最佳电压。并对比数值结果与理论结果分析讨论以上的测量数据,发现数值方法与实验结果符合很好。更多还原

【Abstract】 Nematic liquid crystal (NLC) is an excellent nonlinear photorefractive material with high performance. The properties of materials are improved greatly by doping them with dye. Nematic liquid crystal has a large non-linear coefficient, so it is possible to produce optical phase conjugation (OPC) wave in right condition. Since 1980s, a number of scholars have done optical phase conjugation experiment using liquid crystals. In this paper, degenerate four-wave mixing method is adopted to produce OPC wave. OPC properties of Methyl red-doped and C60-doped nematic liquid crystal are researched by theoretical and experimental studies.Four-wave coupled equations in nematic liquid crystal have been derived using combination of the refractive index grating formed by incident coherent light and Maxwell’s equations. According to the magnitude of absorption coefficient, analytical solution and numerical solution have been obtained.E7+1%MR and E7+0.5%C60 LC cell were prepared in our experiments. The photorefractive orientationnal properties of two samples have been analyzed. Optical circuit for degenerate four-wave mixing used in phase conjugation has been set up. OPC wave was measured in different experimental conditions including the sample thickness, probe and pump light angle, incident light polarization, applied voltage and so on. And the best experimental conditions have been obtained.Based on the best experimental conditions,the change of OPC wave and response time characteristics were measured in detail under the influence of the variation of optical power. Saturation effect was found in OPC changing with incident light power. And permanent grating was formed in E7+1%MR samples, transient grating was formed in E7 +0.5%C60 samples. Voltage characteristics of E7 +0.5%C60 samples have also been researched. And experiment data has been discussed compared to numerical and analytical results.更多还原