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题名	PW装置前端展宽器的设计与高阶色散的研究
作者	杨鑫
学位类别	硕士
答辩日期	2005
授予单位	中国科学院上海光学精密机械研究所
导师	谢兴龙
关键词	超短脉冲 展宽器 惆啾脉冲放大 群速度色散 色散补偿
其他题名	Design of the stretcher and study on high-order dispersion on Petawatt laser system
中文摘要	在PW激光系统中，高峰值功率激光脉冲的产生必须做到有效的从增益介质中抽取能量，从而获得有效放大；同时又必须克服在放大过程中极高峰值功率给放大器带来的损伤，这就是几乎所有的高峰值功率超快激光系统都采用了惆啾脉冲放大技术（C队）和脉冲压缩的原因。本论文工作的重点是脉冲展宽器的设计与实验。我们还针一对设计的反射式单光栅展宽器建立了数学模型，进行了较为全面的数值模拟计算。概括起来，主要研究成果如下： 1．设计了反射式单光栅展宽器。2．用光线追迹法给设计的展宽器建立了数学模型，并进行了较为全面的数值模拟，包括：1）利用这个模型对展宽器中元件失调对展宽器二阶色散和输出光束发散角的影响，以及展宽器中球面反射镜和光栅尺寸的有限大小对带通的影响进行了模拟计算。发现当平面反射镜Ml的纵向偏离角为0．2度时，展宽器的二阶色散量最大；偏离角大于或小于0．2度时，展宽器的二阶色散量随之减小，得到了元件失调会增加输出光束发散角的结论。并发现展宽器中衍射光栅和球形凹面镜尺寸的有限大小对带通有限制作用。提出了利用反射镜Ml纵向的适当偏离增大展宽器二阶色散量的方法，以及增大衍射光栅和球形凹面反射镜尺寸来提高展宽器带通的方法，从而进一步减少展宽过程中的光谱剪 切。2）通过数值模拟计算，分析了残留的高阶色散和B积分对输出脉冲波形和强度对比度的影响，以及不同量值的残留色散和B积分对输出脉冲波形和强度对比度的不同影响，从而找到了各阶色散量对输出脉冲波形和信噪比产生明显影响的临界值。3）从理论上对PW激光系统的几种色散来源进行了分析和讨论，采用数值拟和的方法获得了钱玻璃和Kg玻璃折射率公式的系数，推导了表征各阶色散的导数的表达式，并对PW激光驱动器增益介质钦玻璃和由Kg玻璃加工的光学元件引入的附加高阶色散量进行了计算。通过对亚皮秒脉冲的展宽和压缩进行模拟，发现放大过程中引入的高阶色散对输出脉冲质量的影响可以近似忽略。3．分析和讨论了色散的补偿问题，并提出了有效的补偿方法。4．使用这个展宽器我们在实验中成功的从脉宽为lOOfs，谱宽为16nm的超 短种子脉冲中提取了谱宽为0．4nm，脉宽为500Ps的激光脉冲。展宽后的脉冲仍具有较好的输出质量，基本达到了实验的预期要求。
英文摘要	In the Petawatt laser system, the generation of high peak-power pulse must make it possible to extract energy efficiently from the gain medium, while avoiding very hgih peak-power in the amplification process itself, which may do damage to the optical amplifier. This is the reason why nearly all high peak-power, ultrafast laser systems make use of CPA (Chirped Pulse Amplification ) technique, followed by optical compression. This paper mainly works on the design of pulse stretcher and pulse stretching experiment with it. We set up a theoretical model for the newly designed single-grating stretcher and a numerical program to fully study the process of pulse stretching and compressing. The main works are summarized as followings: Designed a new single-grating stretcher. We set up a theoretical model for the newly designed single-grating stretcherbased on ray-tracing and a numerical program to fully study the process ofstretching and compressing: By this theoretical model, effects of misalignment of optical elements ofstretcher on the second dispersion and on the deviation angle of theoutput pulse are analyzed firstly. The constrains of the finite size of thediffraction grating and the concave mirror in the stretcher on spectrumbandwidth are also considered. It is found, when the misalignment anglefor the plane reflective mirror Ml is 0.2 degree, that the seconddispersion of the stretcher will reach the maximum. Increasing ordecreasing misalignment angle , the second dispersion of the stretcherwill decrease. That inicates the misalignment of optical elements of thestretcher increases deviation angle of output pulse. In conclusion, newways of increasing second order dispersion by misaligning reflectivemirror ,or improving bandwidth by increasing size of the diffractiongrating and the concave mirror in the stretcher are proposed. Effects of the residual high order dispersion and B integraJ on outputpusle, and different quantity of residual high order dispersion on outputpusle and B integral are simulated and analyzed. Several kinds of dispersion resourses in the Petawatt laser system are PW analyzed theoretically. The coefficients of refractive equation are achieved for Nd:glass and K9 glass by numerical fitting method. The derivative of every order dispersion is obtained by diffrentialing the refractive equation to the wavelength. It can be seen that, high order dispersion generated in the amplification process has no effect on sub-picosecond output pulse approximately. We studied and analyzed the problem of dispersion compensation, and thepresent effective compensation method. A lOO-ps(FWHM) Gaussian pulse is successfully stretched to 500ps intemporal with this stretcher, and output quality of stretched pulse is satisfied.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/16602]
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	杨鑫. PW装置前端展宽器的设计与高阶色散的研究[D]. 中国科学院上海光学精密机械研究所. 2005.

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