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题名	飞秒激光成丝诱导电晕放电的实验研究
作者	魏迎霞
学位类别	硕士
答辩日期	2015
授予单位	中国科学院上海光学精密机械研究所
导师	王铁军
关键词	飞秒激光 飞秒光丝 等离子体 光丝诱导电晕放电
其他题名	Experimental investigation of filament guided corona discharge in air
中文摘要	飞秒激光自诞生以来，一直受到人们的关注，其在空气中的传输也是科学家研究的热点。由于飞秒激光脉冲极短的持续时间和极高的峰值功率，在空气传输中会产生很多不同的非线性现象和光学过程。其中，由克尔自聚焦效应和等离子体散焦效应动态平衡形成的等离子体通道，又称飞秒光丝，以其独特的性质和巨大的应用潜力被广泛地研究。激光引雷是飞秒光丝的一个重要应用，超短脉冲激光在空气传输形成的飞秒光丝是一条连续性好、低电阻的长程导电通道，以引导闪电沿安全的路径释放。 虽然激光引雷的研究开展了几十年，但是到目前为止，飞秒光丝诱导高压放电的物理机制还不清楚，并且也没有建立完善的理论模型，因此利用实验室模拟高压环境进行激光诱导高压放电的相关研究变得尤为重要。 本论文主要工作是设计了一套激光诱导高压放电的实验系统，利用此系统研究了光丝诱导电晕放电的荧光表现和演化过程。并在这个系统的基础上进行优化，设计了一套温度气压可控的激光诱导高压放电的模拟系统，这套系统通过改变法拉第笼内温度和气压可模拟不同的实验环境，用于不同条件下激光诱导高压放电的实验研究。在实验室现有条件下，利用激光参数为1 kHz/800 nm/25 fs飞秒脉冲聚焦成丝进行诱导电晕放电的实验研究，用数码相机拍摄电晕放电和激光诱导电晕放电随电压或者激光能量的动态变化，并测量了电晕放电、飞秒光丝和光丝诱导电晕放电三种情况下不同条件的荧光特性，分析了光谱成分和光谱表现的区别，讨论了电晕与飞秒光丝的耦合作用随激光能量或者电晕放电电压的变化情况。通过这些数据分析可以知道，飞秒光丝比电晕放电更容易电离空气中的氮分子，激发氮离子辐射出特征荧光谱线，而激光诱导电晕放电中的氮离子谱线几乎都来自于飞秒光丝的贡献。光丝诱导电晕放电产生的荧光较电晕放电或者飞秒光丝强烈，这是由于光丝与电晕电荷之间存在强耦合作用。当升高电压或者激光能量，光丝与电晕电荷的相互作用加剧，沿光丝产生了更多的电晕放电。这对于我们理解激光与电压的强耦合作用提供了帮助。
英文摘要	The technology of femtosecond lasers has attracted great attention since it was firstly invented，and the propagation of femtosecond laser pulses in air has also become a hot spot issue. With ultrashort duration and extremely high peak power, femtosecond laser pulses are intense enough to induce nonlinear optical effects when propagating in air. Specially, the plasma channel, also named as filament induced by ultrashort laser pulse, which is due to the dynamic balance between Kerr self-focusing effect and plasma defocusing effect, has been widely investigated due to its unique properties and great potentials for applications. Laser-guided lightning is one of the important applications of femtosecond laser-induced filament. The filament forms a long conducting channel with good continuity and low resistance which can guide lighting along a safe path to a safe place. The mechanism of laser-guided lightning has not been fully understood yet and a universally-fitted theoretical model has not yet been proposed so far, although the investigation on it has been conducted for several decades. Therefore, it is our motivation and also a good opportunity for us to do some basic research on filament guided high voltage discharges in the lab. In this thesis, we designed an experimental system according to the principle of Farady cage for investigation of filament guided high voltage discharge. By using this specially designed system, we studied the spectroscopic behavior and dynamic evolution of the filament-guided corona discharges. In addition, a simulation system with temperature-pressure controlled for filament guided high voltage discharge was invented on the basis of the simple system introduced above. This simulation system can simulate different experimental environment for laser-induced high-voltage discharge under different experimental conditions by changing the temperature and pressure inside. As for the experimental investigations in the laboratory, a 1 kHz/800 nm/25 fs laser pulse was focused to produce a filament for the study of filament-guided corona discharge. The typical images of corona discharge and filament guided corona discharge were recorded by a digital camera under the different experimental conditions, for example, discharging voltage and filamenting pulse energy. In addition, the ?uorescence from the corona discharge, filamentation and filament-guided corona discharge was measured, respectively. A comparison of spectral components and spectroscopic behavior, has been made and the interaction between laser filament and high voltage corona discharge changing with high voltage or laser pulse energy has also been performed. Through the analysis of these data, we concluded that laser filament could be more efficient to ionize air nitrogen molecule and excite nitrogen ions leading to ionic fluorescence emission. The ionic fluorescence from filament guided corona discharge is mostly from the contribution of filamentation. Laser filament guided discharge produced nitrogen fluorescence more efficiently than the pure corona discharge process or the pure filamentation process due to the strong interaction of laser filament and corona discharge. When increasing the voltage or the energy of the femtosecond laser pulse, stronger interaction of corona discharge and filamenation, and more corona discharges guided along laser filament were generated. The results can be useful to understand the strong interaction between laser filament and high voltage field.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/16896]
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	魏迎霞. 飞秒激光成丝诱导电晕放电的实验研究[D]. 中国科学院上海光学精密机械研究所. 2015.

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