结构光场的传输特性及其应用

发布时间：2018-02-17 03:58

本文关键词： 角谱法矢量光场艾里光束偏振态自旋角动量　出处：《浙江理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：光是一种电磁波,以麦克斯韦方程为基础的经典电磁场理论可以用来解决光的衍射、传输等问题。虽然目前来说,光场标量衍射理论对于大多数光学传输的实际问题仍然有效,但是伴随着近场理论光学的逐渐完善与发展,标量近似的光学理论本身的不自洽矛盾越来越突出,尤其是近年来,随着半导体二极管激光器、微腔激光器、微光学、近场光学和光子晶体等的迅速发展,实际工作中也需要用较为严格的矢量理论来处理一些应用领域的近场光场特性。本文主要研究与传统标量场区别的矢量光场,即在光场的横截面的偏振态分布是不一致的光场。本文的研究方法是基于电磁波的矢量衍射理论。首先通过矢量衍射理论的角谱分析法和近似法分析了艾里光束的矢量结构特征和偏振态沿径向变化的圆柱型矢量光场在自由空间的传输特性,通过理论计算以及数值计算给出了整个衍射空间的精确矢量解,并且分别分析了其在自由空间的传输特性。主要研究内容分为以下三个部分进行说明:1.利用矢量角谱法和近似法推导、分析电磁场不同分量传输的解析表达式。以Airy光束(艾里光束)为研究对象,研究艾里光束的矢量结构特征,发现艾里光束的横向能量流密度与纵向能量流密度之比随着传播距离的增大而增大的。在菲涅尔衍射区域,TM(横磁模)分量的能量流密度与TE(横电模)分量能量流的比值随着传播距离的增加而逐渐增加,这个比值由λ和横向分量尺寸大小x0决定。该光场的矢量结构特征从艾里光束的传播动力学的物理图像给予进一步进行阐述和分析,这些结果可以为艾里光束在相应领域的潜在应用提供理论依据和基础,如纳米光子学、紧聚焦光场等。2.基于角谱法分析了偏振态沿径向变化的圆柱矢量光场的近场特性。其倏逝波和行波的矢量结构提供了一个直观的图像来描述该矢量光场在近场的特征。其中详细分析了纵向分量对总光场分布的影响以及对光自旋角动量(SAM)的密度影响。经过数值计算发现,具有不同偏振拓扑核的矢量光场的倏逝波和行波的光场分布结构是不同的,并且与光场横截面的初始偏振态分布密切相关。纵向分量的存在,对光学自旋角动量密度的影响,导致了自旋角动量密度的一个矢量分布结构。该研究成果为如何通过在光场横截面上选择适当的偏振态分布,在近场空间操纵矢量光场的光场分布和角动量密度提供非常有用的信息。3.利用USB3.0外设控制器设计了一种图像采集设备的固件,开发光场的数据采集、成像设备,期望最终实现能够利用矢量光束进行数据采集和成像,进一步研究矢量光束的潜在应用。
[Abstract]:Light is a kind of electromagnetic wave. The classical electromagnetic field theory based on Maxwell's equation can be used to solve the problems of light diffraction and transmission. Although at present, the scalar diffraction theory of light field is still valid for most practical problems of optical transmission. However, with the gradual improvement and development of near-field theoretical optics, the self-consistent contradiction of scalar approximation optical theory is becoming more and more prominent, especially in recent years, with semiconductor diode lasers, micro-cavity lasers, micro-optics, With the rapid development of near-field optics and photonic crystals, it is necessary to use more strict vector theory to deal with the characteristics of near-field light in some application fields. In this paper, the vector light field, which is different from the traditional scalar field, is mainly studied. In this paper, the method is based on the vector diffraction theory of electromagnetic wave. Firstly, the theory of angular spectrum analysis and approximate method of vector diffraction theory are used to analyze the Ellie beam. And the propagation characteristics of the cylindrical vector light field in free space that the polarization state changes along the radial direction, The exact vector solution of the whole diffraction space is obtained by theoretical calculation and numerical calculation. The transmission characteristics in free space are analyzed respectively. The main research contents are divided into the following three parts: 1.The vector angular spectrum method and approximate method are used to deduce, The analytical expression of the propagation of different components of electromagnetic field is analyzed. The vector structure of Airy beam (Ellie beam) is studied. It is found that the ratio of transverse energy flow density to longitudinal energy flow density increases with the increase of propagation distance. In Fresnel diffraction region, the energy flow density of TMM component and the energy flow of TEM component increase with the increase of propagation distance. As the propagation distance increases, This ratio is determined by 位 and the size of the transverse component x 0. The vector structure characteristics of the field are further described and analyzed from the physical images of the propagation dynamics of the Ellie beam. These results may provide a theoretical basis for the potential applications of Ellie beams in the corresponding fields, such as nano-photonics. Based on the angular spectrum method, the near-field characteristics of the cylindrical vector light field with polarized state varying along the radial direction are analyzed. The vector structure of evanescent and traveling waves provides an intuitive image to describe the vector light field in the near field. The influence of longitudinal component on the distribution of total light field and on the density of optical spin angular momentum (SAM) are analyzed in detail. The distribution structure of evanescent and traveling waves of vector light field with different polarized topological nuclei is different, and it is closely related to the initial polarization state distribution of the cross section of the light field. The existence of longitudinal component affects the optical spin angular momentum density. This results in a vector distribution structure of the spin angular momentum density. The research results show how to choose the appropriate polarization state distribution on the cross section of the light field. The distribution of light field and angular momentum density of vector light field in near-field space is very useful. Using USB3.0 peripheral controller, the firmware of an image acquisition device is designed, and the data acquisition and imaging equipment of light field is developed. It is expected that the vector beam can be used for data acquisition and imaging, and the potential applications of vector beam can be further studied.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O436

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