全矢量光场的产生及其应用

发布时间：2017-12-31 08:25

本文关键词：全矢量光场的产生及其应用　出处：《南京大学》2016年博士论文　论文类型：学位论文

【摘要】：随着激光技术的发展进步,人们越来越多地认识到光所携带的丰富信息可以作为探测和感知物质世界的手段。若要充分发挥光子作为信息载体的优势,对光场的调控至关重要。光场调控主要包括在时间域和空间域对光场进行调控两大类,调控的光场参量主要是频率、振幅、相位和偏振。在时间域可以调控光场的频率。对光场的振幅、相位和偏振分布的调控构成对光场的空域调控,这也是本论文的主要研究内容。在光学的发展历程中,对振幅和相位的调控技术已经比较成熟有效,而对偏振的调控相对较难,特别是要同时实现对振幅、相位和偏振的调控就更为复杂。通过偏振自由度的引入加之对振幅和相位的调控,无疑会导致光场演化以及光与物质相互作用的新效应。本文将集中研究对光场空间参量的完全调控也即全矢量光场的产生及其应用。本论文工作的主要创新如下：1.提出了一种振幅、相位和偏振可被同时完全调控的矢量光场生成方案。论文回顾了前人提出的基于4f系统和空间光调制器的矢量光场产生方案,该方案的原理是光束的先分解后合成,基模的高斯光束经过空间光调制器和空间滤波后变为两束偏振方向相互垂直的基矢量光,而后这两束基矢量光通过一个Ronchi光栅合成为一束矢量光。在之前的方案中,受空间光调制器工作模式的限制,只能调控两个基矢量光场的相位分布,不能调控其振幅分布,这样就只能调控所合成光场的偏振和相位而不能调控光场的光强分布；而且所合成的矢量光场的偏振态只能位于Poincare球的一个大圆上,不能覆盖整个Poincare球。为了突破上述局限,我们采用了光场复振幅的纯相位编码算法,可以利用相位型空间光调制器完全调控两个基矢量光场的振幅和相位,因此可以实现对由它们所合成的矢量光场的振幅、相位和偏振的完全调控,也就是可以产生全矢量光场。论文中提出的全矢量光场生成方案,是普遍适用的。要产生任意所需的矢量光场,首先将其分解为偏振正交的两个基矢量光场,然后使用纯相位编码算法编码两个基矢量光场的复振幅,最后通过基于4f系统的矢量光场生成系统来生成这一光场。我们设计了相应的实验验证了该方案的实用性和可靠性。2.提出了一种聚焦光场的逆向设计方案,实现了对焦场空间参量的完全调控。焦场设计要解决的主要问题是如何获得与焦场对应的入射场,现今被普遍采用的方案,一种是迭代方案,一种是正向方案。正向方案本质上是一种试探方案,根据经验主动改变入射场的结构来获得所需的焦场。但是由于试探过程复杂,而且只对某些特定类型的焦场有效,因而该方案应用范围有限。而迭代方案是一种近似方案,而且迭代的收敛性与焦场具体结构有关；此外,迭代过程中要求至少有一个光场参量作为自由参数,因而不能用于全矢量光场的设计中。由于正向设计和迭代设计都比较费时,所以很难用在需要对焦场进行实时动态调控的场合。本论文中提出的全矢量焦场的设计方案,是通过逆向计算获得与焦场对应的入射场的。逆向计算的基础是Richards-Wolf矢量衍射理论以及根据坐标变换获得的光场在物镜出瞳和入瞳之间的转换矩阵；在逆向算时可使用快速傅里叶变换和啁啾变换,以保证计算的快速和准确。在逆向设计方案中,入射场的获取仅需一步计算,不需要试探,不需要设定自由参数,因而该方案可以实现对焦场的实时动态的全矢量调控。我们通过实验验证了该设计方案的有效性和普适性,论文还首次提出并使用逆向设计方案在焦场中产生了完美矢量涡旋光场。3.提出了一种基于剪切干涉的相位涡旋拓扑荷检测方案。此方案不仅可以用于标量光场相位涡旋拓扑荷的检测,还可以用于矢量涡旋光场的相位拓扑荷检测。该方案是将带相位涡旋的光场通过一个平行偏振分束镜后一分为二,所产生的两束光的传播方向平行且偏振态相互垂直,而它们的光束中心有一个横向平移。通过这两束光的偏振干涉条纹就可以判断出涡旋的大小和手性。该方案用于检测标量光场相位涡旋拓扑荷时,干涉条纹中围绕两个光强奇点的干涉臂的数目相等且与相位涡旋拓扑荷的绝对值相等,而干涉条纹的方向对应拓扑荷的正负；用于矢量涡旋光场的相位拓扑检测时,围绕两个光强奇点的干涉臂的数目,分别反映两个正交圆偏振偏振分量所携带的相位涡旋拓扑荷的绝对值,而干涉臂的方向则分别反映相位涡旋拓扑荷的正负,通过两个正交偏振分量的相位拓扑荷,就可以逆推出矢量涡旋光场的相位涡旋拓扑荷。相比于其它检测涡旋拓扑荷的方法而言,基于剪切干涉的涡旋拓扑荷的检测方案的优点是,该检测方案不依赖于具体的光场产生光路,可以独立构建和使用；所用元器件精简,光路搭建十分方便；抗干扰能力强,因为我们的光路不要求对涡旋光的中心进行对准,各元件的距离也没有特殊要求,只需要依次通过各个光学元件,就可以产生足够区分不同拓扑荷的实验现象；通过这些现象不仅能区分拓扑荷的大小也能区分拓扑荷的正负；并且不需要对CCD所记录的图像进行后续处理,甚至某些情形下,相位拓扑荷可以用肉眼直接分辨出来；此外,该方案中所用核心元器件具有很大损伤阂值,可以用于高功率情况下涡旋相位拓扑荷的检测。我们通过实验验证了所提出的拓扑荷检测方案,并证实该方案对相干光和部分相干光都有效。
[Abstract]:With the development of laser technology, more and more people realize that the rich information carried by the light can be used as detection and awareness of the physical world. To give full play to the advantages of photon as the information carrier, the regulation is vital field. Mainly includes the regulation of light field in time and space domain of light field regulation two large, light field control of frequency, amplitude, phase and polarization. The frequency of light field can be controlled in time domain. The light field amplitude, phase and polarization distribution of spatial regulation of light field, is the main research contents of this paper. In the course of development of optics. The amplitude and phase control technology is relatively mature and effective regulation of the polarization is relatively difficult, especially the amplitude, phase and polarization control is more complicated. The polarization degree of freedom by introducing The control of amplitude and phase, will undoubtedly lead to evolution of optical field and the interaction between light and matter. This paper will focus on the new effect of light field space parameters completely namely regulation of generation and application of the vector field. The main contributions of this dissertation are as follows: 1. a vector amplitude, phase at the same time and polarization can be completely control the light field generation scheme. This paper reviews the previous proposed 4f system based on spatial light modulator and optical field vector generation scheme, the principle of the project is the first beam after the decomposition synthesis, Gauss beam mode through spatial light modulator and spatial filtering into base vector light beams the polarization direction perpendicular to each other, then the two beam based vector light through a Ronchi grating synthesis for a beam of light vector. Before scheme, by the spatial light modulator working mode limit, only control two The base phase vector light field distribution, can not control the amplitude distribution, so it can only control the synthesis of light field polarization and phase and intensity can not control the light field; a great circle and the synthetic vector light field polarization than in the Poincare sphere, cannot cover the entire Poincare. In order to break the ball limitations, we use a light field complex amplitude phase encoding algorithm, the amplitude and phase using phase spatial light modulator completely control two base vector light field, it can be achieved on the synthesis by the vector light field amplitude, phase and polarization adjustment, is also can produce the full vector light field. The full vector light field generation scheme is universally applicable. To produce any desired vector light field, firstly, it can be divided into two basic vector orthogonal polarization light field, and then use the pure phase A complex amplitude encoding algorithm encoding two base vector light field, finally to generate a light field based on the vector 4f system of light field generation system. We designed the experiment to verify the practicability and reliability of the.2. scheme presents a reverse design focused light field, to achieve a complete regulation focusing field space parameters. The main problems of coke field design to solve is how to get the incident field corresponding to the focal field, is now widely adopted, an iterative scheme is a scheme, is positive. The positive solution is essentially a kind of tentative plan, take the initiative to change the structure of the incident field to obtain the focal field according to the required experience. But because the test process is complex, and only on certain types of focal field effectively, thus the scheme of limited application range. And the iterative scheme is an approximation scheme, and iterative convergence and focal field The structure of the body; in addition, the iterative process requires at least one light field as a free parameter, so it can not be used to design the full vector light field. The forward design and iterative design are more time consuming, so it is difficult to use in the field of real-time dynamic control need to focus the occasion. The design scheme of the vector field of coke in this paper, is obtained by reverse incident and corresponding focal field. Based on the reverse calculation of Richards-Wolf vector diffraction theory and coordinate transformation to obtain the optical field in the objective lens and the entrance pupil of the pupil conversion matrix according to the calculation can be used in reverse; fast Fourier transform and chirp transform, to to ensure fast and accurate calculation. In reverse design, access to the incident field only one step calculation, no need to test, do not need to set the free parameters, so the scheme can realize the focusing field. Full vector dynamic regulation. We experimentally verify the validity of the design scheme and universality, this paper also put forward for the first time and the use of reverse design in the focal field produces a perfect vector optical vortices.3. proposed a measuring scheme for phase vortex shear interference detection based on topological charge. This scheme not only can for the detection of scalar light field phase vortices of the topological charge, can also be used for phase topological vector optical vortices bearing detection. The program is going through a parallel polarization beam splitter with phase vortex after One divides into two. light field, the propagation direction of light beams generated by the parallel and perpendicular polarization, and their beam the center has a transverse translation. We can estimate the vortex size and chirality by the polarization of the two laser beams interference fringes. The scheme for the detection of scalar light field phase vortices of topological charge, the interference fringe around An equal number of interference arms around two light intensity and phase singularities of the vortex topological charge is equal to the absolute value, and the positive and negative direction of the interference fringes corresponding to the topological charge for phase detection; topological vector vortex optical field, the number of interference arms around two intensity singularities, the absolute value respectively reflect the two orthogonal circle polarization component with phase vortices of topological charge, and the direction of interference arms respectively reflect the positive and negative phase vortices of topological charge, the phase topology of two orthogonal polarization components of charge, you can launch the inverse phase vortices of topological vector optical vortices. Compared to other methods for load detection of vortex topological charge, advantages vortex shear interference detection scheme topology based on the load, the detection scheme does not depend on the specific light field produced light path, can be built and used; components used in optical structures is very streamlined, Convenient; strong anti-interference ability, because we do not require the optical path of the vortex center alignment, each component distance also has no special requirements, only need to loop through each optical component, they can produce enough to distinguish the experimental phenomena with different topological charges; distinguish topological charge size can also distinguish negative topological charge by these phenomena can not only; and does not require the recorded images to the CCD for further processing, and even in some cases, phase topological charge with the naked eye can distinguish; in addition, the core components used in the scheme has very high damage threshold, can be used for the detection of high power vortex phase topological charge. We to verify the proposed topology load detection scheme by experiment, and the scheme of coherent and partially coherent light are effective.

【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O436

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