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题名	飞秒激光脉冲在透明介质中的非线性传输特性研究
作者	徐凤
学位类别	硕士
答辩日期	2007
授予单位	中国科学院上海光学精密机械研究所
导师	刘建胜
关键词	飞秒激光脉冲 自聚焦 等离子体细丝通道 X波 锥形辐射 脉冲压缩
其他题名	Study on Nonlinear Propagation Characteristics of Femtosecond Laser pulse in Transparent Media
中文摘要	近年来，飞秒激光脉冲在透明介质中传输的研究引起国内外研究小组的广泛关注。飞秒激光脉冲在透明介质（固体、液体和气体）中传输时引起介质的高阶非线性效应，导致介质折射率的改变，从而极大地影响了激光束在透明介质中的传输性质。飞秒激光脉冲在透明介质中的传输具有广泛的应用，诸如光脉冲压缩、光学参量放大、产生超连续谱白光、大气污染监测、人工引雷放电、激光等离子体天线以及高次谐波的产生等。飞秒激光在透明介质中的传输是研究超快高强度激光物理领域的重要研究课题，它涉及到各种激光电离机制、非线性传输效应等问题的研究，其成果具有重要的科学意义。目前，飞秒激光脉冲在透明介质中的传输研究已成为各国科研人员关注的热点。 本文对飞秒激光脉冲在透明介质中传输的非线性以及成丝的一些特点进行了理论研究，包括克尔效应、群速度色散、多光子电离和多光子吸收等对传输的影响。同时实验上开展了飞秒激光在空气中产生等离子体通道的寿命研究。本论文主要取得了以下几点创新性的成果： 1． 对飞秒激光在透明介质中的传输模型采用稳定的Crank-Nicolson差分格式编写程序进行了数值模拟。分析了在不同入射功率条件下，飞秒激光在水中传输时各种非线性效应的作用。解释了飞秒激光在水中X波的形成原因，并且在频域分析了锥形辐射的特征以及其与X波的关系。 2．数值模拟了飞秒激光在水中传输时的脉冲压缩和超连续谱的形成，分析了多光子电离和多光子吸收对超连续谱的影响。 3． 在实验上研究超强飞秒激光脉冲在空气中传播形成的等离子体细丝通道的若干特性，如电导率、长度、寿命。利用外加高压电场的方法实现等离子体细丝通道寿命的延长。 4．在实验上，采用双脉冲和多脉冲技术，以进一步延长等离子体细丝通道的寿命，实验结果表明了使用飞秒脉冲序列来延长等离子体细丝通道寿命的可行性。
英文摘要	Recently, the study on propagation characteristics of femtosecond laser pulse in transparent media has been a hot topic over the world wide. When a femtosecond laser pulse propagating in a kind of transparent media (including solid，liquid and gas), it can induce high-order nonlinear effects. These effects will influence the propagation property of the laser pulse greatly because it can change the refractive index of the media. Femtosecond laser pulse’s propagation in transparent media has been widely used in compression of laser pulse, optical parametric amplification, white light production, detection of air pollution, manual inducing of lightening, laser-plasma antenna, generation of high-order harmonics, etc. Propagation of femtosecond laser pulse in transparent media is a very important topic in ultra-fast high-intensity laser research. It deals with the topics of laser ionization and nonlinear propagation effects, and can give meaningful results. This paper concentrates on the theoretical study of nonlinear propagation of femtosecond laser pulse in transparent media. The effects of self phase modulation, optical Kerr effect, group velocity dispersion, multi-photon ionization and multi-photon absorption on the propagation have been discussed. On the other hand, the lifetime of plasma channel produced by the filamentation of fs laser in air has been experimentally investigated. The paper presents the following new results: 1. Made the numerical simulation of nonlinear propagation of femtosecond laser pulse in transparent media with the stable Crank-Nicolson difference formulation. Analyzed the nonlinear effects of femtosecond laser pulse propagating in water at different input powers, and the cause of the X-wave’s formation in water, then analyzed the formation of conical emission and the relationship between it and X-wave. 2. Numerically simulated the generation of pulse compression and supercontinuum, analyzed the influence of multi-photon ionization and multi-photon absorption on the supercontinuum. 3. After the plasma channel was induced by laser pulse, the characteristics of the plasma channel such as electric conductivity, length and lifetime were studied. By adding an external electrical field, the lifetime of plasma channel was prolonged. 4. Used the double-pulse and multiple-pulse technique to prolong the life-time of plasma channel in the experiment. It shows the feasibility of prolonging the life-time of plasma channel with femtosecond laser pulse sequence.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/16532]
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	徐凤. 飞秒激光脉冲在透明介质中的非线性传输特性研究[D]. 中国科学院上海光学精密机械研究所. 2007.

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