【作者】 韩小红；

【导师】 杨艳芳；

【作者基本信息】 上海大学 ， 无线电物理， 2011， 硕士

【摘要】 有限光束由光密介质入射到光疏介质界面处发生全反射时,实际的反射光束相对于几何光学的反射光束存在一段侧向位移,该位移被称作Goos-H(a|¨)nchen (GH)位移。近年来,有限光束被不同的光学微结构反射的规律得到了人们的重视和大量的理论研究。在实验上对于GH位移的测量也进行了大量的研究,主要有:多次反射来增大位移,位置灵敏探测器,微波法测量GH位移等。本文利用液晶光阀和光束分析仪实现了棱镜全反射GH位移的简单而精确的测量,并与用稳态相位法进行的理论计算进行了分析对比。为基于GH效应设计新型光学开关等光学器件提供诸多可能。矢量光束由于其特殊的偏振分布,当与物质相互作用时会产生一些特殊的效应。尤其经过高数值孔径聚焦后可以得到一些独特的聚焦场性质,例如可以产生很强的纵向场、很小的焦斑尺寸、光学囚笼等。这对我们认识和了解物质的属性和光束(光子)的本质提供了新的途径,具有丰富的研究内容。围绕古斯-汉欣位移和空间偏振变化矢量光束,本文主要作了两部分工作:一是提出了基于液晶光阀和光束分析仪测量GH位移的简单方法;二是空间偏振变化矢量光束的生成和强聚焦性质的研究。对于这两部分工作,主要分三部分来讨论:1.设计和改造了GH光学微小位移的实验系统。新的实验方法是一种基于液晶光阀和光束分析仪的简单测量,该方法将测试精度提高到了纳米量级。实验中研究了液晶光阀对光偏振态调制的特性,结果表明当外接电压发生变化时,光的偏振态也随之变化。利用液晶光阀对光偏振态的调制和光束分析仪记录光斑重心位置的变化,我们能直接测量出TE和TM两种偏振态入射时棱镜单界面反射光束的GH位移差。结果表明,实验结果与理论结果很吻合。2.空间变化偏振矢量光束的生成。首先调节偏振转换器,将入射的线偏振光束转换为角向或者径向偏振矢量光束并实现二者的转换;然后将径向偏振或者角向偏振光束经过液晶可调相位延迟器就可以得到空间偏振变化矢量光束。由于液晶相位延迟器由外部电压直接控制,使其相位延迟角度δ能在0到π之间连续取值,因此能通过实时控制液晶相位延迟器的相位延迟角度在0到π之间连续变化实现对空间偏振分布矢量光束的实时改变。3.空间偏振变化矢量光束强聚焦性质的研究。数值孔径角α和光瞳半径与光束束腰半径比β决定了光束的聚焦能力,但聚焦强度并不与α和β成简单的正比关系。本文数值模拟分析了α与β变化时对纵向场强的影响,得到了最大纵向聚焦场对应的α与β的取值。用最佳值α与β数值模拟了空间偏振变化矢量光束强聚焦时在焦平面上的场分布。结果表明聚焦场强烈依赖于相位延迟角度δ。当液晶相位延迟器的δ在0到π之间变化时横向场强分布基本不变,但纵向场强分布有很明显的变化。因此调节液晶相位延迟器的驱动电压可以实现对焦平面上的纵向场强的实时调控。更多还原

【Abstract】 Bounded beam totally reflected from an interface between two different dielectric media may undergoes a lateral shift from the position predicted by geometrical optics. This phenomenon was referred to the Goos-H(a|¨)nchen (GH) effect. In recent years, people has attached great importance and done a great deal of research to the rule of limited light beam reflected by different optical microstructures. People also offer a lot of studies on experimental measurement of GH shift, such as: multiple reflections to increase displacement, position sensitive detectors (PSD), microwave method for measuring the GH displacement etc. This paper has simply and precise measured the GH shift of total reflection in prism by the light crystal light valve (LCLV) and the light beam profiler (LBP), compared and analyzed with the theoretical calculation. For the potential applications in new optical devices such as optical switches.As the vector beams has special polarization distribution, some innovative properties may happened when it has interaction with matters. Especially when it is tightly focused, we can gain some particular properties, such as can form a strong longitudinal field, can form a smaller spot size, optical cage and so on. This has great research significance and provide us new path to know and understand the properties of matters and the essence of the light beam.Base on research of GH shift and spatial-variant states of polarization vector beams, this paper has mainly completed two parts works: firstly, a novel approach to directly observe the small optical beam shift(GH shift)based on LCLV and the LBP; secondly, research of the generation and tight focusing properties of spatial-variant states of polarized vector beams. For the two parts job are mainly divided into three parts to discuss:1. Design and modify the experimental system of small optical shift GH. The novel experimental approach is a simple measurement based on LCLV and the LBP, which can be raised the accuracy of experiment result to nanometer scale. We studied the optical modulation characteristics of LCLV in experiment, and the results show that the polarization states of light changed when external voltage changes. The difference between the TM and TE polarized longitudinal GH shift at the condition of total internal reflection on a prism-air interface can be modulated the polarization state of the beam by the LCLV and detected by LBP registered the barry center of the beam. This method doesn’t need complex external processing circuit, and the experimental result shows good agreement with theoretical calculation.2. The generation of spatial-variant states of polarized vector beams. Firstly, adjust the polarization converter, convert the linearly incident polarized beam into radially or azimuthally polarized beam and changed between them. Then the spatial-variant states of polarized vector beams can be obtained when radially or azimuthally polarized beam after the Liquid Crystal Variable Retarder (LCVR). As the LCVR are controlled by external voltage, we can obtain the continuous retardation angleδfrom 0 toπ, therefore the polarized distribution can be continuously changed by varying retardation angleδfrom 0 toπin real-time.3. Research of tightly focusing properties of spatial-variant states of polarization vector beam. The magnitude of the intensities strongly depends on the focusing angleαand the ratio of the pupil radius and the beam waistβ. However, the focusing intensity is not proportional toαorβ. In this article, we simulated and analyzed the impact to longitudinal electric field intensity whenαandβchanges, got the maximum longitudinal focus field and the corresponding optimum value ofαandβ. Then, we numerically simulated the transverse and longitudinal electric field intensity of spatial-variant states of polarized vector beams in the focal plane with the optimum value ofαandβ. The numerical results indicate a strong dependence of the field near the focus on the phase retardation angleδ. The evolution of the transverse focal pattern has little changes when the phase retardation angle changes from 0 toπ, while the longitudinal focal pattern is varied remarkably. Therefore,the longitudinal focal pattern can be continuous changed by varying retardation angleδfrom 0 toπin real-time.更多还原