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题名	飞秒激光脉冲时域形状测量和对比度研究
作者	申雄
文献子类	博士
导师	刘军
关键词	飞秒激光 femtosecond laser pulses 时域形状 temporal profile 时域对比度 temporal contrast 瞬态光栅效应 Transient-Grating 自衍射效应 Self-Diffraction
其他题名	Research on temporal profile characterization and temporal contrast of femtosecond laser pulses
英文摘要	本文的主要工作在于飞秒激光脉冲时域形状测量和对比度的研究。 在绪论中，我们叙述了激光的简要发展；并对于激光脉冲的数学定义作了简要的说明；另外，对宽于飞秒量级事件的时间计量作了普适性简述；也对飞秒激光脉冲时域对比度的提升和测量意义做了说明。 在飞秒激光脉冲时域形状测量研究中，我们回顾了飞秒激光脉冲时域形状测量发展历程。随后，鉴于自参考光谱干涉（Self-referenced spectral interferometry, SRSI）方法所具有的众多优势，对这一测量方法进行了深入研究。最后，基于瞬态光栅效应（Transient-Grating, TG）在自参考光谱干涉方法的优势，研制出了多种各有优势的测量装置： （1）高灵敏度TG-SRSI，SRSI利用三阶非线性效应来产生自参考光，使得其对于低能量脉冲的测量比较困难，基于TG效应所具有的较高灵敏度，我们利用TG-SRSI实现了亚纳焦的飞秒激光脉冲测量； （2）直筒式TG-SRSI，提出了一种直筒式的紧凑TG-SRSI测量装置，用来对飞秒激光脉冲进行测量，装置中的光学元件在套筒里面呈直线型分布，这避免了对光路的复杂调节，增加了测量装置的稳定性和实用性； （3）全反射式TG-SRSI，成功的解决了SRSI测量过程中比较严重的三个问题，具有较大的优势：（a）装置所使用的光学元件除了三阶非线性介质外，都为反射式光学元件，这使得装置可以实现周期量级的飞秒激光脉冲测量；（b）装置对待测激光脉冲能量和与其他光束的相对时间延迟进行独立的调节，使得该装置更易使用，操作简易；（c）凹球面反射镜垂直式的光束聚焦也避免了利用抛物面反射镜光束聚焦所带来的表面散射的影响（d）该装置在结构上目前也相对比较紧凑，外观尺寸为293×170×83 mm3，其平面尺寸略小于一张A4纸的大小。 在飞秒激光脉冲时域对比度提升的研究中，首先，从原理上论证了自衍射效应（Self-Diffraction, SD）作为一种简并四波混频过程在脉冲时域对比度提升上所具有的潜力, 自衍射信号时域对比度约为入射激光脉冲时域对比度的三次方，即C_(SD+1≈) C_in^3；其次，搭建了两套自衍射信号产生装置，提升了所产生自衍射信号的时域对比度和脉冲能量，实现了7个数量级以上的对比度提升，并获得了单边780 μJ，转化效率为7.8%的一级自衍射信号输出；然后，对于三阶非线性介质片的表面散射对于对比度提升的影响也做了探索，我们发现，三阶非线性介质片的表面散射对于对比度提升具有影响，利用两种表面粗糙度不同的介质，所得到的SD信号对比度相差一个数量级；最后，利用一块单棱镜对自衍射信号的空间角色散进行了补偿。 在飞秒激光脉冲时域对比度单发测量研究中，首先，我们对飞秒激光脉冲的时域对比度测量发展做了较为详细的论述；然后，提出了基于时域对比度降低技术来实现单发高动态范围时域对比度测量的新方法，作了详细的研究，并对一时域对比度为107的激光脉冲进行了测量。结果表明，通过降低待测激光脉冲的时域对比度，从而实现单发高动态范围对比度测量具有一定的可行性。进一步降低待测激光脉冲的时域对比度是该项研究工作的核心内容，利用该方法实现高于1010的单发时域对比度测量仍处于探索过程中。; This dissertation is focused on the research on temporal profile characterization and temporal contrast of femtosecond laser pulses. In the introduction, we start with a brief exploration of the development of laser. Then we provide the mathematical definition of laser pulses in both temporal and frequency domain. A popular science on the evolution of duration measurement is presented in the third part of the section for a better understanding of temporal profile characterization of femtosecond laser pulse. At last, we point out the vital role of temporal contrast enhancement and characterization of femtosecond laser pulses for ultrafast and ultraintense laser systems. In the research on temporal profile characterization of femtosecond laser pulses, we review the measurement methods widely used briefly. Self-referenced spectral interferometry (SRSI) has turned out to be an analytical, sensitive, accurate, and fast method for characterizing the temporal profile of femtosecond pulses. We review the underlying principle and the recent progress in the field of SRSI. Because of the advantages of transient-graing (TG) process in SRSI, based on TG-SRSI, three equipments with different advantages have been developed: (1) High sensitivity TG-SRSI. SRSI needs third-order non-linear processes to used for the generation of self referenced pulse, which makes the method difficult to characterize pulses with low pulse energy. As TG is more sensitive than the other two processes, we build a TG-SRSI device, and characterize pulses with sub-nJ energy. (2) Tube-type TG-SRSI. An economical, compact and alignment-free device based on TG-SRSI is proposed to realize the measurement of femtosecond laser pulses. The entire optical setup is composed of two lens and two glass plates on a straight line with tubes, thereby avoiding the complicated adjustment of the optical path and improving the stability and practicality of the device. (3) Reflective TG-SRSI. It has the advantages below: (a) No transmission element is used, and the device can characterize pulses as short as few-cycles; (b) Energy attenuation and time delay of the pulse to be characterized can be adjusted separately, which makes the device more easy to be adjusted. (c) Concave reflective mirror is used for pulse focusing with low affect from scattering noise. (d) It has a compact structure with dimensions as 293×170×83 mm3. As the temporal contrast of the self-diffraction (SD) signal is the cube of that of the incident pulse C_(SD+1≈) C_in^3 in theory, SD process is used in the temporal contrast enhancement of femtosecond laser pulses. In the research of temporal contrast enhancement based on SD process, cylinder reflective mirrors are used to increase the incident pulse energy to multi-millijoules, SD signal with 780 μJ pulse energy and 5 orders of magnitude temporal contrast improvement is generated. In the research, we found that the scattering effect from the Kerr medium can not be neglected for high temporal contrast enhancement. The linear angular dispersion of a SD signal is studied and compensated for by the use of a single prism. We give a presentation on the evolution of temporal contrast measurement of femtosecond laser pulses in detail. A characterization method based on temoral contrast reduction is proposed. The method posseses a relative higher dynamic range than SRSI-ETE and a pulse with temporal contrast as 107 is characterized by this method. However, it still can not meet the requirement of ultrafast and ultraintens laser systems. The key point in this method is to reduce the temporal contrast of pulses be measured.
学科主题	光学工程
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/31036]
专题	中国科学院上海光学精密机械研究所
作者单位	中国科学院上海光学精密机械研究所
推荐引用方式 GB/T 7714	申雄. 飞秒激光脉冲时域形状测量和对比度研究[D].

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