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题名	飞秒强激光在介质中的成丝及其应用研究
作者	鞠晶晶
学位类别	博士
答辩日期	2012
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	超强飞秒激光脉冲 非线性传输 成丝 水凝结 雪花 异核团簇 频谱展宽 超宽蓝移 拍瓦 钳制强度
其他题名	Intense Femtosecond filamentation and their applications
中文摘要	自1995年，自Braun等人相继在液体和固体中发现了激光传输造成的损伤以来，飞秒强激光脉冲在介质中的非线性传输以及成丝，就快速成为物理学中一个非常重要的研究领域，近年来，随着激光技术的不断发展，特别是啁啾脉冲放大技术的发明，目前，人们已经能够获得脉宽小于5 fs，功率密度为1022W/cm2的超短超强激光脉冲，这种高强度的激光脉冲与物质的相互作用，又激发了很多新的研究热点，比如高能量粒子的产生，有效中子源产生，以及超强飞秒激光非线性传输过程中新特性的研究等。这些研究在很多方面有着重要的应用，例如大气遥感，人工引雷，台式核聚变，台式中子源等。 本论文主要对飞秒强激光脉冲成丝诱导水凝结以及降雨/雪，TW激光脉冲与异核甲烷团簇相互作用后产生的透射光谱展宽以及蓝移，以及PW激光脉冲在大气中的非线性成丝过程中的强度钳制效应等问题进行了实验以及理论研究。主要内容包括： 1. 利用1-kHz飞秒激光在威尔逊扩散云室中成丝，首次成功实现激光诱导水凝结和人工降雨/雪。证明了高重复频率的激光脉冲成丝后，在光丝周围引起剧烈的气流运动，是诱导高效以及宏观尺度的水凝结和降雨、雪的重要因素； 通过改变成丝周围的温度和湿度分布，发现低温和高湿度是诱导高效水凝结和降雨雪的重要条件；通过对云室充氩气后成丝诱导降雪量的分析，发现吸湿性H2O-HNO3的浓度不是制约降雪量的唯一因素； 利用特斯拉线圈放电模拟大气雷电，取代激光成丝来诱导水凝结，发现激光成丝与大气闪电诱导的光化学反应类似，排除了激光成丝诱导水凝结中HNO3的产生而引起的酸雨的可能性。 2. 对TW飞秒强激光脉冲与甲烷团簇相互作用的透射光谱的测量发现了超宽蓝移，并发现该超宽蓝移谱的短波尽头有对比度较高（»23）的独立“蓝”谱峰。实验以及数值模拟结果证明：甲烷团簇对入射激光能量的有效吸收，以及团簇内分子的高阶电离，是透射光谱向短波方向产生较大频移的主要原因。 3.对PW量级激光在大气中的非线性成丝的后向散射光信号的测量，验证了超强PW飞秒激光在成丝过程中依然遵循强度钳制效应。同时，通过记录激光束离开聚焦透镜的不同距离处的光斑分布图，发现入射激光能量为4J时，相比50 mJ 时的光斑分布质量有了很大的提高。
英文摘要	The study on nonlinear propagation and filamentation of intense femtosecond laser pulses has become one of the most important areas in physics science since Braun et al: observed damages caused during laser propagation in both liquid and solid media in 1995. The fast development of this area really depends on the advance of laser technology, especially the advent of chirped-pulse amplification technique. The pulse duration has reduced from a few tens of picoseconds n the mid-1980s to a state-of-the-art shorter than 5 fs with an intensity of 1022W/m2. Many new hot spots have been triggered by such intense laser, including high energy particles production, effective neutron source, long distance self-guiding propagation of intense laser pulses, new features of ultra-intense femtosecond laser pulse propagation etc. All these researches might possess a number of useful applications, such as table-top nuclear fusion, table-top neutron source, atmospheric remote sensing, lighting control, and so on. This thesis is devoted to theoretical and numerical studies of the intense laser pulses with high repetition inducing water condensation and precipitation, super continuum spectrum of transmitted laser lights for laser-hetero cluster interactions under different gas backing pressure and intensity clamping effect of PW femtosecond laser pulse propagation in air. Main items include: 1. We firstly realized laser induced water condensation and precipitation by filamentation of a 1 kHZ, 9 mJ, 50 fs laser pulse in a Wilson-type diffusion cloud chamber. We found experimentally that high-repetition laser-filamentation induced violent movement of moist air current around the filaments was a key parameter to induce efficient and macroscopic scaled condensation and snow formation. By controlling temperature and humidity distribution around the laser filaments, we found that low temperature and high humidity were necessary for an efficient laser-filamentation-induced condensation and snow formation. By filling the chamber with argon gas, the concentration of the binary H2O-HNO3 was found not as critical as expected to induce condensation and snow formation. We also used discharging of Tesla coil to replace the laser filaments. This result demonstrated that what happens between laser filaments and air was similar to that between lighting and air and laser-filamentation-induced water condensation should not lead to acid rain in outside atmosphere in the future. 2. By imaging the transmitted lights of TW laser pulses interacting with hetero-cluster-methane cluster into a grating spectrometer, we found large spectral blue shifting in the transmitted spectra and outstanding ''''blue'''' peak at the end of the new short wavelength side. Experimental and simulation results showed that the largely blue shifted transmitted laser spectra were ascribed to efficient energy absorption of laser energy and high charged ions generation. 3. By measuring the backing scattering fluorescence intensity of PW laser pulse propagation in air, we found the high input energy of laser pulse could not improve the intensity inside a filaments, which confirmed the intensity clamping effect for ultra-intense laser pulse. We also found the beam profile quality for laser energy of 4 J was improved largely comparing with that for laser pulses of 50 mJ.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15681]
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	鞠晶晶. 飞秒强激光在介质中的成丝及其应用研究[D]. 中国科学院上海光学精密机械研究所. 2012.

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