【作者】 荣振宇；

【导师】 国承山；

【作者基本信息】 山东师范大学 ， 光学， 2014， 博士

【摘要】 振幅、相位和偏振是光场的三个重要调控参量。经典的标量衍射理论主要涉及光波的振幅和相位参量，而不考虑偏振态的影响。近年来随着研究的不断深入，光场的偏振态在研究光子的本质属性及光与物质的相互作用中起到了越来越重要的作用。对光波偏振特性的研究使得设计新的具有偏振选择和调控特性的光学元件或光学系统变得越来越重要。通常，将偏振态在空间中呈非均匀分布的光场称为矢量光场。矢量光场的衍射及其与物质的相互作用的新效应拓展了其在生物光子学、超分辨率成像、数据存储、光纤通信、光学微操纵等领域的应用。正是由于矢量光场的新颖特性及其潜在的应用前景，使得对矢量光场的研究在近几年有了突飞猛进的发展。在这一研究领域，如何将一束普通的高斯光束调制为一束具有所需要的偏振态非均匀分布的矢量光场是一项基础研究工作。本论文针对矢量光场的生成及其调控进行了理论分析和实验研究，主要研究内容如下：1.综述了目前已有的矢量光场的生成方式。根据生成矢量光场的方法中是否有增益介质，分为主动式和被动式，介绍了一些典型的利用双折射晶体、Brewster光学元件、偏振选择腔镜等手段进行腔内模式选择来实现矢量光场的例子；另外，还介绍了利用Mach-Zehnder干涉仪光路、Sagnac干涉仪光路、衍射分光光学元件干涉光路等基于干涉手段实现偏振调控的例子；特别是随着光电子技术的发展，在传统的干涉手段中引入可程控光学元件实现光路的动态调控，介绍了在这一研究方向的最新进展。2.基于径向偏振矢量光场和旋向偏振矢量光场的两个正交线偏振分量及合成光场的偏振态分布的计算机模拟，逐步将所讨论的矢量光场的分布特性推广到具有偏振态空间非均匀分布以及混合偏振态形式的一般矢量光场，为实验研究如何调控矢量光场提供设计基础。3.基于程控液晶空间光调制器在光场动态调控中的应用，系统阐述了液晶的基本理论，并以液晶的连续弹性体理论为基础分析了液晶分子指向矢的模拟计算方法。根据论文后续工作的需要，以编号ZLI-4792的液晶材料及差分迭代算法为基础，通过计算机模拟研究了液晶池参数、迭代参数等对液晶指向矢空间分布计算的影响，确定了最佳液晶模拟计算参数。4.基于液晶的琼斯矩阵理论，对液晶池在关态和开态下的琼斯矩阵进行了数值计算，并以此为基础定量地验证了液晶的“波导效应”。重点以液晶在开态下的琼斯矩阵元与驱动电压的关系为基础，详细分析了液晶的调制特性，说明其显示灰度与驱动电压的关系，并模拟了其对入射线偏振光的振幅、相位及偏振态的调制作用，分析了液晶光学系统在商用配置模式、纯振幅调制配置模式和纯相位配置模式下的振幅、相位调制曲线，利用理论计算模型为设计实验提供必要的参数。5.以实现矢量光场调控为目的，开展了优化液晶空间光调制器调制特性的分析研究。理论分析表明，采用单个液晶空间光调制器难以直接实现对两个正交偏振分量的振幅、相位和偏振态同时调制。提出了基于Mach-Zehnder干涉仪光路的双通道正交偏振分量调制模式，通过模拟计算确定适于液晶光学系统输出两个正交偏振分量的系统配置条件；为了改进Mach-Zehnder干涉仪光路的缺陷，进一步提出了双级联液晶空间光调制器的设计思路，并通过计算模拟确定了适用于在级联系统中实现双通道正交偏振分量调制的液晶光学系统的配置条件，为实验工作的开展奠定了理论基础。6.根据理论分析结果，实验建立了基于双级联液晶空间光调制器的矢量光场调控实验系统。利用琼斯矩阵理论分析了双级联液晶空间光调制器的调制特性及双通道计算全息图的设计原理；分析结果表明该系统能够对输出矢量光场的两个正交偏振分量的振幅和相位进行双通道的、独立的控制。基于该实验系统和专门设计的双通道偏振选择计算全息图，不仅实验生成了各种典型的矢量光场，成功实现了具有“无衍射特性”的矢量Bessel光束和同时具有偏振涡旋和相位涡旋的矢量光学涡旋等新型矢量光场。此外，利用该实验系统还能实现偏振奇点与相位奇点在空间中的二维调控，为进一步研究光子的自旋角动量与轨道角动量的转化提供了很好的实验条件。更多还原

【Abstract】 Amplitude, phase and polarization are important parameters of optical beams which can bespatially modulated. It considers only the amplitude and phase of optical beams in classicalscalar diffraction theory without any consideration for the polarization. In recent yearspolarization property has played an important role in researching the nature of light and itsinteraction with materials. The study on the polarization of optical beams makes it important todesign optical devices and optical system with polarization-selective and polarizationcontrolling characteristic. The optical beams with inhomogeneous polarization distributiongenerally named vector beams. Vector beams’ propagation and interaction with materials haveextensively extended the application in the field of biophotonics, superresolution imaging, datastorage, optical communications and optical manipulation. Because of their interestingproperties and potential applications, there has been a rapid increase of study on vector beams.How can we transform a Gaussian beam to a wanted vector beam with spatially variantpolarization is a foundational work. The objective of this dissertation is to develop a newmethod to generate and control of vector beams in theoretical analysis and experimentalresearch. The main points of this dissertation are as follows:1. The general methods to generated vector beams have been introduced. The ways togenerate vector beams classified into active way and passive way depending on whether ornot involving amplifying media. The active methods realize the intracavity polarized modeselection with aid of the optical birefringence, Brewster optical elements, polarizinggrating mirror and so on. The passive methods rely on interferometry are mainlyintroduced include the Mach-Zehnder interferometry, the Sagnac interferometry andinterferometry based on diffractive optical elements. With the rapid development ofphotoelectronic technique, the programmed optical elements are introduced into thetraditional interferometry to realize the dynamic controlling.2. Simulating the polarization states distribution of the orthogonal linearly polarizedcomponents and their superposition basing on the radially polarized beams and azimuthalpolarized beams. The analysis is extended to the vector beams not only possess the polarization inhomogeneous distribution but also consist of hybrid polarization.3. The liquid theory and the simulation the distribution of liquid crystal directors areintroduced basing on the liquid crystal spatial light modulator applied to optical beamscontrolling. According to the requirement of the theoretical analysis, the differenceiterative method is used to calculate the distribution of liquid crystal directors, take thecode: ZLI-4792for example, from which we can approach the optimal parameters of theliquid crystal cell and its iterative algorithm.4. Numerically simulating the Jones matrix of the liquid crystal cell on ‘off’ state andanalysing the wave-guided effect of liquid crystal. Numerically simulating the relationshipbetween the Jones matrix of the liquid crystal cell on ‘on’ state and the applied voltage.Revealing the relationship between the gray levels displayed on the liquid crystal displayand the applied voltage by analyzes the modulating characteristic of liquid crystal cell. Wealso simulate the results by modulating the amplitudes, phase and polarization of theincident optical beams. We numerically calculate the modulating curve of the commercialmode, pure amplitude-modulating mode and pure phase-modulating mode which canprovide the optimal parameters for the designing of the experimental system.5. We optimize the modulating characteristic of liquid crystal spatial light modulators inorder to generate and control the vector beams. Firstly we confirm that single liquid crystalspatial light modulator can’t realize the controlling of the amplitude, phase andpolarization modulating of the orthogonal polarized components directly andsimultaneously. After that a double-pass orthogonal polarization modulating mode basedon the Mach-Zehnder interferometry is proposed and we find the optimal systemparameters for this condition. At last, we present the design of cascaded liquid crystalspatial light modulators to improve the fault of the previous interferometry and discuss theoptimal system parameters in this condition.6. We present the configuration of the vector beams generating and controlling system basedon the cascaded liquid crystal spatial light modulators. We analyse the modulatingcharacteristic of the cascaded system and the design of a double pass computer generatedhologram. The analysis indicates that we can realize the double pass and independentcontrol of the amplitude and phase of the orthogonal linearly polarized components withthe help of the double pass computer generated hologram and the cascaded liquid crystalspatial light modulators. The experiment results demonstrate that the system can carry outthe designed operation on the orthogonal linearly polarized components. We achieve thevector Bessel beams which possess the non-diffractive characteristic and the vector beams with helical phase distributions which possess polarization vortices and optical vorticessimultaneously. The most important is that we can achieve the2-D control of thepolarization singularity and the phase singularity in the beam cross section. We hope thiscascaded system can provide a convenient way to study the properties of other complexvector beams and the interaction between the optical spin angular momentum and opticalorbital angular momentum in experiments.更多还原