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chi20190523上海光机所王铁军557543Femtosecond laser filamentation is a universal phenomenon that takes place during the propagation of an ultrashort ultra-intense laser in an optical medium. Due to its unique physical characteristics, laser filament finds applications in a wide range, such as remote sensing, THz generation, guiding corona discharge, pulse compression, and water condensation et al. The physical picture of the filamentation is complex in the sense that there are many nonlinear processes happening simultaneously. From the application point of view, it is beneficial to have a comprehensive understanding of the key parameters of filamentation. The intensity inside the filament is one of the most critical parameters for the development of filament related applications. While the direction measurement of the intensity inside the filament is a challenging mission. In this thesis, we focus on direct measurement of clamping intensity by the so called “burning pinhole” method, which includes the following three contents: Firstly, a systematic study on pulse duration dependent clamping intensity inside femtosecond filament was investigated. A direct measurement on clamping intensity inside laser filament was performed. The result shows that the clamping intensity is gradually decreased with the pulse duration stretching from 45 fs to 177 fs. The experimental results are in a good agreement with the simulation results by solving the extended nonlinear Schr?dinger equation. The pulse duration sensitive clamping intensity inside filament offers an important factor towards fully understanding the intensity related filament applications. Secondly, polarization dependent on clamping intensity inside femtosecond filament was experimentally measured in air. In virtue of the alike “burning pinhole” method, the measured clamping intensity inside laser filament is gradually increased up to 1.7 times by tuning the laser pulse ellipse from linear polarization to circular polarization. The polarization sensitive clamping intensity inside filaments offers an important factor towards fully understanding the polarization related phenomenon observed so far. Finally, an attempt on the measurement of the intensity radial distribution inside the filament core influenced by the initial laser intensity distribution is presented. By gradually raising the shoots of input laser pulses and measuring transmission energy of the pre-ablated pinhole, the filament core radial intensity distribution has been measured experimentally. The measured intensity distribution is significantly modulated by the incident laser after passing through a small aperture. The experiment results offer an important factor towards the fully understanding of filamentation process and open a new area of filamentation with intensity modulated in radial direction.2019atalunwen21965233814273Femtosecond laser filamentation;Intensity Clamping;Chirp; PolarizationInvestigation of the Clamping Intensity inside the Femtosecond Filament in Air Based on Burning Pinhole Measurement基于烧蚀法的飞秒激光大气成丝钳制光强的研究飞秒激光成丝现象是超短超强激光脉冲在光学介质中传播时常见物理现象。因其具有的独特物理特性,飞秒光丝在很多领域有着潜在的重要应用,例如远程遥感,THz 产生,诱导电晕放电,脉冲压缩,诱导水凝结等。由于飞秒激光成丝过程中多种非线性过程同时作用,为充分理解成丝过程背后的具体物理图像带来了困难。从应用角度出发,对于充分理解成丝过程中各重要参数是十分重要的。 光强是研究飞秒激光成丝内部物理机制与开展应用研究的重要参数,然而对其进行直接测量却是一项充满挑战性的工作。本文的主要工作就是基于烧蚀针孔的直接测量方法,对成丝过程中的钳制光强现象进行了研究。 本文研究了脉宽依赖的光丝内部钳制光强特性。利用烧蚀针孔的方法,对于不同脉宽成丝内部钳制光强进行了直接的实验测量。实验发现当脉宽逐渐展宽(由 45 fs 展宽至 177 fs) 时,对应的钳制光强逐渐减小。并且实验结论与通过求解非线性薛定谔方程得到的数值模拟结果符合得较好。脉宽依赖的钳制光强的特性和分析,为深入理解脉宽相关的光丝应用提供了科学依据。 此外,本文研究了大气飞秒激光成丝过程中钳制光强对入射激光偏振状态的依赖关系。实验中同样利用烧蚀针孔的方法,实验发现,当入射激光偏振状态由线偏逐渐变化为圆偏时,测量得到的光丝内部钳制光强逐渐升高为线偏时的 1.7 倍。偏振依赖的光丝内部钳制光强研究为充分理解偏振相关的成丝现象提供了指导。 最后,本文还初步研究了入射激光光斑径向强度分布对于光丝核心强度分布的影响。通过逐渐改变预烧蚀针孔的直径,测量透过能量,实验发现,光斑初始的径向强度分布会对成丝区域的强度分布造成调制。关于调制的光丝核心强度径向分布讨论,有利于充分理解成丝的物理过程,为与光强相关的成丝应用提供了新的思路。飞秒激光成丝;钳制光强;啁啾;偏振依赖中国科学院上海光学精密机械研究所张旋光学工程硕士
中文题目: 基于烧蚀法的飞秒激光大气成丝钳制光强的研究
外文题目: Investigation of the Clamping Intensity inside the Femtosecond Filament in Air Based on Burning Pinhole Measurement
作者: 张旋
导师姓名: 王铁军
学位授予机构: 中国科学院上海光学精密机械研究所
答辩时间: 20190523
中文关键词:
飞秒激光成丝;钳制光强;啁啾;偏振依赖
英文关键词:
Femtosecond laser filamentation;Intensity Clamping;Chirp; Polarization
中文摘要:
英文摘要:
文献类型:学位论文
学位级别: 硕士
正文语种: chi
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