1、 大气湍流论文：光束在湍流大气中的传输【中文摘要】激光在光通信、遥感、监测等方面具有越来越广泛的应用,因而关于激光光束在大气湍流中传输特性的研究具有非常重要的意义。由于湍流扰动的影响,光束在大气中传输会发生光强起伏变化、像点抖动、光束扩散等大气湍流效应。正是这些湍流效应的影响,在大气中传输的光束质量会大大降低。如何减少湍流大气对光束的影响已成为一个重要的研究课题。寻求一种特殊的光束以减少湍流效应一直是广大学者的研究方向,许多不同激光束在湍流中传输特性的研究已见诸报端。本文对大气湍流的基本理论进行了简要的叙述,介绍了湍流大气的相关参数及几种主要的大气折射率功率谱模型,对湍流效应中的光强起伏即闪烁
2、指数的计算进行了介绍,为研究光束在湍流大气中的传输做了理论准备。结合鬼成像的实际应用中的大气环境,对湍流大气中部分相干光的鬼成像进行了理论研究,根据经典光相干理论和广义惠更斯-菲涅尔积分,得到了在大气湍流环境中部分相干光的鬼成像解析公式,分析了光源相干长度、传输距离、湍流强度对鬼成像质量的影响。研究表明:光源光斑越大,鬼成像质量越好;而湍流强度、光源相干长度及光源与待成像物体间距离的增加,均会降低鬼成像质量。具有螺旋相位因子的光束被称为涡旋光束,涡旋光束中的光子携带有轨道角动量,可以利用光子的轨道角动量进行信息编码,并应用于自由空间光通讯,因而研究涡旋光束在大气湍流中的传输特性具有重要的意义。
3、本文利用闪烁指数测量仪测量了涡旋光束闪烁指数,并比较了高斯光束和不同拓扑荷数涡旋光束的闪烁指数变化,分析了拓扑荷数对闪烁指数的影响。实验表明:在相同湍流环境下,涡旋光束闪烁指数比高斯光束闪烁指数小,且拓扑荷数越大,光束的闪烁指数越小。高阶高斯贝塞尔光束同时具有无衍射特性和携带轨道角动量,其产生和传输也引起了学者的极大兴趣,利用空间光调制器和轴棱锥产生的高阶高斯贝塞尔光束,论文分析了高阶高斯贝塞尔光束在模拟大气湍流中的传输。研究表明:由于大气湍流的影响,即使在无衍射区内,高斯贝塞尔光束也会发生扩束现象,而轨道角动量的存在会降低湍流对光束的影响。【英文摘要】The propagation of l
4、aser beams in a turbulent atmosphere has attracted much attention due to its widely important practical applications, such as in connection with remote sensing, monitoring and optical communication. The refractive index fluctuation causes a variety of effects on an optical wave while propagating in
5、turbulence. Therefore, there has been much research on the ways of reducing the turbulent effects on the propagating optical beam.In this thesis, the basic theory and some parameter of atmosphere turbulence, scintillation index and some important power models for refractive-index is introduced, whic
6、h give a basis theory for the work of wave propagation in the turbulent media.According to the applied environment of ghost image, ghost imaging with partially coherent light radiation through turbulent atmosphere has been studied. The analytical ghost imaging formulas have been derived based on the
7、 classical optical coherent theory and the extended Huygens-Fresnel integral. The influence of the turbulence strength, propagation length, the sources transverse size and coherent width on the quality of the ghost imaging has been discussed. It is found that the larger the sources transverse size i
8、s, the better the quality of the ghost imaging. When the turbulence strength, propagation length and the sources coherent width increase, the quality of the ghost imaging decrease.Beams with spiral phase are regarded as vortex beams. Each photon of vortex carries orbital angular momentum (OAM), whic
9、h can be used in information encoding. The study on the propagation property of vortex beams in turbulence is very important. The scintillation index of vortex beams in turbulence has been measured with a scintillation detector. Corresponding properties of a Gaussian beam and vortex beams with diffi
10、rent topological charge propagating through the same atmospheric turbulence conditions are detected for comparison. The experimental data shows that vortex beams have inferior scintillation properties when compared with a comparable Gaussian beam and the scintillation index decreases with the increa
11、sing of the topological charge.Due to the the beam carries a vortex phase factor and nondiffracting, the generation and the propagation of Bessel beams is another subject that attracts much attention. The spatial light modulator(SLM) and axcion was used to generate high-order Bessel beams with desir
12、ed topological charge. The propagation properties of high-order Bessel beams in a turbulent atmosphere has been studied experimentally with the effects of turbulence simulated by a rotated random phase plate. It is found that the high-order Bessel beams spreads due to the turbulence even in the non-
13、diffracting distance. The effects of the turbulence can be reduced with increasing of the the topological charge which is the measure of the orbit angular momentum.【关键词】大气湍流 闪烁 鬼成像 涡旋光束 高斯贝塞尔光束【英文关键词】Atmosphere turbulence scintillation ghost imaging vortex beams Bessel beams【目录】光束在湍流大气中的传输 摘要 3-5 Ab
14、stract 5-6 第一章 引言 9-13 1.1 研究背景 9-10 1.2 论文研究内容及章 节安排 10-13 第二章 大气湍流概述 13-26 2.1 大气湍流的描述 13-15 2.2 大气湍流折射率功率谱模型 15-19 2.3 大气湍流闪烁效应 19-22 2.4 光束在大气湍流中传输的研究方法 22-25 2.5 本章小结 25-26 第三章 部分相干光束在大气湍流中的鬼成像研究 26-40 3.1 鬼成像理论 27-30 3.2部分相干光在大气湍流中的鬼成像 30-35 3.3 数据分析 35-39 3.4 本章小结 39-40 第四章 涡旋光束闪烁指数的测量 40-51 4.1 涡旋光束及其产生 40-42 4.2 涡旋光束闪烁指数的测量 42-49 4.2.1 闪烁测量仪 42-45 4.2.2 涡旋光束闪烁指数 45-49 4.4 本章小结 49-51 第五章 高阶高斯贝塞尔光束在湍流大气中的传输 51-58 5.1 高阶高斯贝塞尔光束的产生及实验装置 51-53 5.2 实验分析 53-57 5.3 本章小结 57-58 第六章 全文结论 58-59 参考文献 59-66 作者在读期间发表论文 66-67 致谢 67
