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题名	自由空间的光束传输特性研究
作者	吴国华
学位类别	博士
答辩日期	2009
授予单位	中国科学院上海光学精密机械研究所
导师	王之江 ; 楼祺洪
关键词	光束 偏振态 相干性 焦移
其他题名	The investigation of beam propagation properties in free space
中文摘要	激光束在自由空间中的传输变换和聚焦特性是激光光学主要研究内容之一，它对激光光学理论和激光技术的发展具有重要意义。本论文从部分相干光的传输理论出发，对光束产生的必要条件，光束在聚焦区的光强分布以及光束在远场的矢量结构分析等做了深入的研究，取得的主要创新成果如下： 1. 基于2×2的交叉谱密度函数矩阵出发，将标量J0相关谢尔模型光束推广到矢量情形。并在此基础上，利用角谱方法和静态位相法，首次推导了产生矢量J0相关谢尔模型光束的必要条件。同时，该条件也适用于标量J0相关谢尔模型光束。该条件对如何产生矢量和标量J0相关谢尔模型光束具有重要的理论指导意义。 2. 研究了单束平顶光束在聚焦区的光强分布。结果表明，平顶光束轴上最大光强总是位于几何焦点之前即存在焦移。其焦移量和系统的菲涅数、光束的模式数等参数有关。同时探讨了多束平顶光束以不同组束方式组束以后，其光强在焦平面的分布。结果发现，非相干叠加情形下，光强分布对归一化半径和菲涅数等参数的依赖性明显小于相干叠加情形。 3. 基于光束相干矩阵，研究了径向偏振光在聚焦区的光强分布。研究结果表明，径向偏振光通过理想薄透镜聚焦后其最大光强总是位于几何焦平面之前，即存在焦移。其焦移量和系统的菲涅数密切相关，但是与线偏振光相比，径向偏振光的焦移量明显大于线偏振光的焦移量。也就是说，偏振态也会影响光束的焦移量。 4. 基于角谱方法和静态位相法，首次研究了空心光束在远场的矢量结构。在远场，将空心光束展开成相互垂直的TE项和TM项。并得到空心光束在远场的能流分布。研究结果表明，空心光束在其传播过程中并不能保持其形状不变
英文摘要	The propagation, transformation and focusing properties of beam are the main topic in modern optics, which plays an important roles in the development of modern optics theory and laser technologies. Starting from the propagation law of partially coherent beam, the beam conditions for radiation generated by an electromagnetic Gaussian-Schell model source, the intensity distribution of beam in focal regions and analytical vectorial structure of hollow Gaussian beams in far field are investigated in details. The main results are listed as follows: 1. Based on the 2×2 (electric field) cross-spectral density matrix, a model for an electromagnetic J0-correlated Schell-model beam is given that is a generalization of the scalar J0-correlated Schell-model beam. The conditions that the matrix for the source to generate an electromagnetic J0-correlated Schell-model beam are obtained. The condition for the source to generate a scalar J0-correlated Schell-model beam can be considered as a special case. The derived conditions are important to understand the theoretical aspects for the source to generate physically, realizable, highly directional electromagnetic J0-correlated Schell-model beams. Also provide constraints for synthesis and simulations of such beams. 2. The intensity distribution of flat-topped beams in focal regions are presented. Results show that the point of the absolute maximum axis intensity always located at a distance from geometric focus and closer to the lens, i. e., exists focal shifts. The focal shifts of flat-topped beams are depend on the beam order N and Fresnel number. Also, the intensity distribution of a radial laser array for flat-topped beam focused by a lens at the focus plane, for phase-locked and nonphase-locked cases, is studied numerically. It is found that intensity distribution for nonphase-locked case is much less sensible to the Fresnel number and normalized radius than that of phase-locked case. 3. Beginning with a beam coherence polarization (BCP) matrix, an analytical intensity expression for radially polarized laser beams that pass through an apertureless aplanatic lens is obtained. The intensity distribution of radially polarized beams in the vicinity of the focus is investigated. Results show that the maximum intensity is located just before the geometric focus, i. e., focal shift occurs. The related focal shift of radially polarized beam is depend on the Fresnel number. However, the focal shift of radially polarized beam are more evident than that of linearly polarized beam when other parameters are the same. That is to say, the focal shift of beam are related the polarization of beam. 4. The analytical vectorial structure of hollow Gaussian beams is investigated in the far field based on the vector plane wave spectrum and the method of stationary phase. The energy flux distribution of hollow Gaussian beams in the far-field, which is composed of TE term and TM term, are demonstrated. Results show that hollow Gaussian beams can''t keep its ring-shape invariant in the propagation.
语种	英语
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15264]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	吴国华. 自由空间的光束传输特性研究[D]. 中国科学院上海光学精密机械研究所. 2009.

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