杂化偏振矢量光束紧聚焦和焦斑整形研究

发布时间：2019-05-17 09:09

【摘要】：光的重要性质中,人们对频率、振幅、相位等几个性质早已进行了深入的研究。近年来,光的另一个重要性质——偏振性成为了人们研究的热点,尤其是对非均匀偏振分布的矢量光束的研究引起了研究人员极大的兴趣。柱矢量光束作为最基本和最简单的矢量光束,由于其独特的聚焦特性和潜在的应用价值得到了人们广泛的研究。如径向偏振光经过高数值孔径透镜紧聚焦后焦区的光场会有非常强的纵向分量,使得其在超分辨聚焦、光存储、光刻等领域有着突出的应用。除了柱矢量光束,最近研究人员生成了按照任意规律分布的局域线偏振矢量光束和同时包含线偏振、圆偏振、椭圆偏振的杂化偏振矢量光束,使得矢量光束得到丰富,为产生新奇的紧聚焦特性提供了可能性。本论文以其中一种杂化偏振矢量光束为研究对象,分别研究了径向变化杂化偏振矢量光束和角向变化杂化偏振矢量光束的紧聚焦特性。然后针对径向变化杂化偏振矢量光束,分别用环形光阑和二元相位元件对其调制,进行焦斑整形的研究。主要的研究内容和结论如下:1.详细介绍了本论文所作研究依据的理论基础——Richards-Wolf矢量衍射理论,这个理论推导出入射光为均匀振幅分布的x方向线偏振光紧聚焦后焦区的光场表达式。我们在此基础上推导出更为普遍的入射光为任意振幅分布的沿x方向和沿y方向偏振的线偏振光经过高数值孔径透镜紧聚焦后焦区的光场表达式。2.分别研究了径向变化杂化偏振矢量光束和角向变化杂化偏振矢量光束的紧聚焦特性。对径向变化杂化偏振矢量光束,研究了线偏振基矢的取向角Ф_0,偏振分布的初相位δ_0和径向指数n对紧聚焦特性的影响。研究发现,取向角的变化会使焦平面上的焦斑旋转相应的角度;初相位的变化会影响焦平面上的焦斑形状;径向指数由小变大时,轴截面上将由一个焦斑分裂成两个焦斑,并且两个焦斑之间的距离随径向指数的增大而增大,同时焦平面上由一个椭圆形焦斑变成一个环形焦斑,并且环的半径随径向指数的增大而增大。对角向变化杂化偏振矢量光束,研究了线偏振基矢的取向角Ф_0,偏振分布的初相位δ_0和角向指数m对紧聚焦特性的影响。研究发现,取向角和初相位的改变产生的影响一致,使得焦平面上的光强分布旋转一定的角度,同时中心光强发生改变;角向指数的改变使得焦平面上形成多个焦斑,焦斑个数为2(m+1)。3.针对n较大的径向变化杂化偏振矢量光束,我们首先用环形光阑对其进行焦斑整形,发现经调制的径向变化杂化偏振矢量光束紧聚焦后能形成光针状光强分布,光针的焦深随径向指数的增大而增长,焦平面上形成椭圆形焦斑,焦斑的椭圆率随径向指数的增大而增大。为了提高光能利用率,我们用二元相位元件对径向指数为1的径向变化杂化偏振矢量光束进行焦斑整形,通过matlab遗传算法对二环到八环相位元件进行优化,调制后得到了光针。光针的焦深随环数的增多而增长,焦平面上的焦斑随环数的增多由椭圆形变为近似圆形。最后通过对光针范围内不同位置横截面光强分布的研究,发现两种方法形成的光针横截面的光强分布沿光束传播方向都存在旋转现象。径向指数的正负控制旋转的方向,取向角的改变能够使光针沿光轴旋转一定的角度。
[Abstract]:In the important properties of the light, the frequency, amplitude, phase and so on have been studied in depth. In recent years, the other important property _ polarization of light has become the hot spot of people's research, especially the research of the vector light beam with non-uniform polarization distribution has caused great interest in the researchers. The column vector beam, as the most basic and simplest vector beam, has been widely studied because of its unique focusing characteristics and potential application value. As the radial polarized light passes through the high-numerical aperture lens, the light field in the focal area can have a very strong longitudinal component, so that it has outstanding application in the fields of super-resolution focusing, optical storage, and photoetching. in addition to that column vector light beam, the most recent researcher generate a local linear polarization vector light beam which is distributed according to an arbitrary rule and a hybrid polarization vector light beam which simultaneously comprises a linear polarization, a circular polarization and an elliptical polarization, so that the vector light beam is rich, A possibility is provided for the creation of a novel compact focusing characteristic. In this paper, a hybrid polarization vector light beam is used as a research object, and the tight focusing characteristics of the hybrid polarization vector light beam and the angular change hybrid polarization vector beam are studied. Then, aiming at the radial variation hybrid polarization vector light beam, the annular optical element and the binary phase element are respectively used for modulating the polarization vector light beam to carry out the research of the focal spot shaping. The main contents and conclusions are as follows:1. In this paper, the theoretical basis of the study and the theory of Richards-Wolf's vector diffraction are introduced in detail. On the basis of this, we derive more general incident light as the light field expression of the focal area after the linearly polarized light polarized in the x-direction and in the y-direction through the high-numerical aperture lens, and the polarized light in the y-direction is focused by the high-numerical aperture lens. In this paper, the tight focusing characteristics of the hybrid polarization vector beam and the angle-direction-varying hybrid polarization vector beam of the radial-varying hybrid polarization vector are studied. In this paper, the influence of the orientation angle of the linear polarization vector, the initial phase angle of the polarization distribution and the radial index n on the tight focusing property is studied. it is found that the change of the orientation angle will cause the focal spot on the focal plane to rotate the corresponding angle; the change of the initial phase will affect the shape of the focal spot on the focal plane; when the radial index is large, the axial cross-section will be divided into two focal spots by a focal spot, And the distance between the two focal spots increases with the increase of the radial index, while the focal plane is changed from an elliptical focal spot to an annular focal spot, and the radius of the ring increases with the increase of the radial index. In this paper, the influence of the orientation angle of the linear polarization vector, the initial phase angle of the polarization distribution and the angular index m on the compact focusing property is studied. It is found that the influence of the change of the orientation angle and the initial phase is consistent, so that the light intensity distribution on the focal plane is rotated to a certain angle, and the central light intensity is changed; the change of the angular index makes the focal plane form a plurality of focal spots, and the number of the focal spots is 2 (m + 1). aiming at the large radial variation hybrid polarization vector light beam, firstly, the annular optical beam is used for shaping the focal spot, and the modulated radial variation hybrid polarization vector light beam is found to be tightly focused, so that the light needle light intensity distribution can be formed, the focal depth of the light needle is increased with the increase of the radial index, An elliptical focal spot is formed on the focal plane, and the ellipticity of the focal spot increases with the increase of the radial index. In order to improve the utilization of light energy, we used the binary phase component to shape the focal spot of the radial variation hybrid polarization vector beam with the radial index of 1, optimize the two-to-eight-ring phase element by the matlab genetic algorithm, and obtain the optical needle after modulation. The focal depth of the light needle increases with the increase of the number of rings, and the focal spot on the focal plane changes from the ellipse to an approximately circular shape with the increase of the number of rings. Finally, the light intensity distribution of the cross-section of the light needle formed by the two methods is found to be rotating in the direction of the beam propagation through the study of the light intensity distribution of the cross-section at different positions in the range of the optical needle. The direction of the positive and negative control rotation of the radial index and the change of the orientation angle can rotate the light needle at a certain angle along the optical axis.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O436.3

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