【作者】 陈鹏；

【导师】 丁良恩；

【作者基本信息】 华东师范大学 ， 光学， 2011， 硕士

【摘要】 超快激光等离子通道(光丝)的产生和传输在过去的十几年中成为了一个热门问题。在近红外飞秒光丝方面的研究取得了令人瞩目的成果,尤其超连续谱、光丝自压缩、多光子电离、锥状辐射等,为获得周期量级的超短脉冲提供了可能。而迄今为止,对于超快脉冲激光成丝的研究基本上是在红外光谱范围内进行的。由于紫外激光成丝阈值低,聚焦性能优越,所以研究紫外激光的成丝特性成为了目前超快激光领域有特色的研究。本论文利用mJ级紫外飞秒激光脉冲光源,研究其光谱、丝长、成丝位置、丝径、能量透过率和成丝阈值等特性,并与近红外飞秒激光成丝特性相比较,进一步验证发展紫外强场光物理的潜在优势,并为开展紫外强场等离子体通道的光谱研究提供有参考价值的数据,这是本论文的主要目标。本人进行了以下实验工作：1、采用了倍频-补偿-和频的共线结构实现晶体中飞秒脉冲的高效谐波转换,优化了其中的相位失配、群速度失配等参数,使三次谐波的转换效率可达到10%,实现了紫外飞秒激光毫焦量级的输出,峰值功率达到10GW级,为进一步研究紫外脉冲激光成丝的实验研究提供了必要条件。2、利用紫外飞秒激光在不同焦距下聚焦产生等离子体通道,重点研究了紫外光丝的成丝特性,包括光丝在成丝前后的光谱变化、成丝长度和成丝位置、丝的直径、能量透过率和成丝阈值等特性,并获得了成丝阈值条件等重要参数。3、通过对近红外激光的成丝特性的补充测量,重点作了紫外和近红外等离子体通道特性的比较和分析。通过实验结果比较得出了以下结论：紫外和近红外激光都有频谱展宽效应；紫外等离子体光丝的成丝阈值明显低于近红外一个量级,聚焦能力也强于近红外；紫外等离子体通道的传输距离比近红外更长等结果。更多还原

【Abstract】 Over the years, the propagation of femtosecond filament in transparent media has attracted considerable attentions. Filamentation in the near-infrared (IR) femtosecond pulse has achieved numerous excellent results, such as the generation of super-continuum from ultraviolet (UV) to IR, multiphoton ionization and conical emission, etc. the pulse self-compression due to filamentation provides the possibility for generation of few-cycle pulse. The UV femtosecond laser pulse has numerous outstanding optical features, such as excellent focus ability, high single photon energy, large ionization rate, and so forth. It is nevertheless somehow difficult to generate high-intensity UV fs pulses, and due to the lack of suitable UV fs sources, researches on UV femtosecond filaments are not as prevailing as those on near-IR filaments.In this thesis, the characterics of spectra, length, filamentation position, diameter, energy transmission and threshold by mJ-level UV femtosecond laser pulse are demonstrated. Compared to the properties of IR femtosecond filamentation, the potential values for developing the strong UV laser pulse are proposed. The main aim of this paper is to provide valuable data for the plasma spectroscopy of ultrafast UV laser.This thesis consists of three parts:1. An approach of frequency doubling-compensation-tripling in collinear structure for femtosecond pulses was designed and employed to fulfill efficient harmonic conversion,optimized the phase and group velocity mismatch and improves the conversion efficiency of third frnquency harmonic, so as to get the level of 10%. We realized the third frequency harmonic of mj and produced the peak power of 10GW lever. This provides the prerequisite for the study of ultrafast UV plasma filaments.2. We focused on the plasma filaments properties of UV in different focal length, such as the spectral change, length,position,diameter, energy change and threshold of plasma filaments,and got into the important parameters of threshold condition.3. The thesis measured characteristics of near-infrared plasma filaments, then make a comparative analysis about UV and infrared plasma filaments. Through experiment we have concluded the following conclusion:the VU and near-infrared plasma filaments have shown that Spectrum broadening effect; The self-focusing threshold of UV pulse is one order of magnitude lower than that of IR pulse. The focusing ability of UV pulse is more excellent than IR. The filaments length of UV pulse is longer than IR.更多还原