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题名	块体材料的自聚焦成丝效应及其超宽超连续谱的产生
作者	杨玉霞
文献子类	硕士
导师	廖梅松
关键词	激光成丝 filamentation 超连续谱 supercontinuum 镧玻璃 lanthanum glass PbF2晶体 PbF2 crystal K5玻璃 K5 glass 非线性 nonlinear
其他题名	Filamentation and supercontinuum generation in bulk materials
英文摘要	近年来，随着超强超快激光技术的不断发展，高功率飞秒激光脉冲与物质的相互作用已成为研究热点，激光成丝及该过程中所产生的多种非线性现象逐渐被人们发现，其中超连续谱的产生就是其中之一。超连续谱的产生是指当高峰值功率的激光脉冲在透明非线性介质中传输时，由于自相位调制、多光子吸收和等离子体散焦等多种非线性效应的共同作用，引起脉冲的光谱发生展宽的现象。作为 一种新型的高亮度宽带光源，超连续谱光源因其在生物医学、光学检测、光谱学以及光学传感等许多领域都具有重要的应用而被广泛研究。块体材料作为最早用来产生超连续谱的非线性介质，因其宽的透射范围、大的体积和低的价格所带来的优势，始终备受研究者们的青睐。本论文主要研究了镧玻璃、氟化铅（PbF2）晶体和K5玻璃这三种具有不同特性的块体材料，在高峰值功率飞秒激光脉冲作用下的激光成丝及超连续谱产生特性。本论文主要包括六章。 第一章为绪论部分，叙述了飞秒激光成丝超连续谱产生的研究进展，介绍了超连续谱产生的影响因素，并提出了本论文的研究思路。 第二章主要介绍了飞秒激光在非线性介质中的传输性质、激光成丝过程中产生的一些有趣的非线性现象以及描述激光成丝过程的三种物理模型。 第三章研究了高峰值功率飞秒激光脉冲作用下，镧玻璃的自聚焦成丝及超连续谱产生特性。在没有透镜聚焦泵浦激光的条件下，得到了20 dB 光谱宽度覆盖400―2800 nm波长范围的超连续谱。此外，考虑到输出光束半径的不稳定性对基于块体材料的超连续谱光源的限制，本章又通过移动焦点模型模拟了输出光束半径随输入脉冲峰值功率的变化。最终，模拟结果表明在一定的输入峰值功率范围内，在镧玻璃的输出端可以得到一个稳定且小的光束半径。 第四章研究了在不同泵浦波长及不同聚焦条件下，PbF2晶体的自聚焦成丝及超连续谱产生特性。在透镜聚焦泵浦激光的条件下，得到了4.7倍频程的超连续谱，且光谱宽度覆盖350―9000 nm。此外，根据激光成丝过程引起介质的光学损伤可以用来制造波导这一原理，建立了波导模型。通过利用分步傅立叶算法求解描述激光脉冲在波导中传输的广义非线性薛定谔方程，模拟了两种不同泵浦波长下，等效波导中的超连续谱产生特性，最终得到了20 dB宽度覆盖350―9000 nm的超连续谱，与实验结果取得了相应的一致性。 第五章通过实验研究了在与第三章相同的泵浦条件下，K5玻璃的自聚焦成丝及超连续谱产生特性，得到了覆盖360－3100 nm波长范围的超连续谱。 最后为论文的结论部分，归纳总结了本论文的主要工作，指出了本论文的创新点，并对未来的工作进行了展望。; In recent years, with the development of the intense ultrashort pulse laser technology, the interaction between high-power femtosecond laser pulse and materials has been a research hotspot. Filamentation and a variety of nonlinear phenomena have been found during the propagation of femtosecond laser pulse in optical media, and supercontinuum generation is one of the phenomena. Supercontinuum generation is a phenomenon when a pulse with high peak power propagates in a nonlinear medium, the nonlinear effects such as self-phase modulation, self-steeping, multiphoton ionization and plasma defocusing work together and make the spectra become broader. As a novel broadband light source with high brightness, supercontinuum source has attracted much attention due to its varieties of applications in many fields, such as biomedical sciences, optical measurement, spectroscopy, and optical sensing. Bulk material as the earliest nonlinear medium used for supercontinuum generation has been one of the favorable media for supercontinuum generation since 1970 due to the advantages brought by its wide transparent band, large volume and low cost. In this paper, the filamentation and supercontinuum generation in three kinds of bulk materials including lanthanum glass, lead fluoride (PbF2) crystal and K5 glass were studied. This paper contains six chapters. In chapter 1, we reviewed the research progress of supercontinuum generation by filamentation. Additionally, we introduced the factors that influence the generation of the supercontinuum, and then came up with the ideas of the article. In chapter 2, the properties of ultrashort pulses propagate in nonlinear media, the properties of light filaments and the models of filamentation were introduced. In chapter 3, we investigated the filamentation and supercontinuum generation in a piece of bulk lanthanum glass when the high peak power femtosecond pulse propagated in it. A broadband spectrum covering the 400–2800 nm wavelength range in a 20 dB dynamic range was obtained without any lens to focus the pump pulse. In addition, considering the instability of the output beam radius restricts the development of the supercontinuum source based on the bulk media, numerical simulation was carried out to investigate the effect of the input peak intensity on the output beam radius in the frame of a moving-focusing model, the simulation results showed that a stable and small beam radius can be obtained at the end of the propagation domain in a certain input peak intensity range. In chapter 4, we investigated the filamentation and supercontinuum generation in a piece of bulk lead fluoride crystal at different pump wavelengths under different experiment conditions. A broadband supercontinuum spanning 4.7 octaves, from 350 to 9000 nm, was demonstrated under the lens focusing the pump pulse. In addition, according to the fact that optical damage during filamentation can be used to write high-quality waveguides inside optical materials, a waveguide model was built. The propagation of a pulse in the equivalent waveguide under two different pump wavelengths were simulated by solving the generalized nonlinear Schr?dinger equation applying the adaptive split-step Fourier method. The width of the spectra covering 350―9000 nm in a 20 dB dynamic range were obtained by simulation. This showed an agreement with the experiment results. In chapter 5, we investigated the filamentation and supercontinuum generation in a piece of bulk K5 glass experimentally under the pump condition the same as the chapter 3. A supercontinuum spectrum covering 360－3100 nm was obtained. The last chapter is the conclusion. Main results of present work were concluded with innovation and shortage being mentioned.
学科主题	光学工程
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/30952]
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	杨玉霞. 块体材料的自聚焦成丝效应及其超宽超连续谱的产生[D].

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