| 题名 | 钛宝石超强超短激光系统色散精密控制技术研究 |
| 作者 | 李帅 |
| 文献子类 | 博士 |
| 导师 | 李儒新 |
| 关键词 | 啁啾脉冲放大 Chirped-pulse amplification 色散控制 dispersion management 展宽器 stretcher 棱栅对 grism pair 光栅压缩器 grating compressor |
| 其他题名 | Research on precision dispersion control of the Ti: Sapphire superintense ultrafast laser facility |
| 英文摘要 | 超强超短激光技术的发展为人类在实验室尺度内创造出前所未有的极端物理条件，对基础学科、前沿交叉学科和光与物质的相互作用等高科技领域的发展，起到了极大的推动作用。随着脉冲啁啾放大技术和光学参量啁啾放大技术的发展，超强超短激光系统所能提供的峰值功率越来越高，聚焦功率密度也越来越强。目前，国际上多个国家地区，如欧盟、法国、英国等已投入巨资竞相开展10拍瓦级超强超短激光系统的研制。建设10拍瓦级超强超短激光系统中的一项难点就是对超强超强激光系统的总体色散进行精密的控制，尽可能地消除高阶色散，从而输出接近于傅里叶变换极限的压缩脉冲，在同样的能量水平下获得更高的脉冲峰值功率。 本论文主要是在参与的国家重大科技基础设施项目“上海超强超短激光实验装置”（SULF），发展其中的10拍瓦级钛宝石超强超短激光系统的基础上完成的。基于10拍瓦级钛宝石超强超短激光系统，对激光系统色散产生机制、常用色散元件以及相应的色散精密控制技术等进行了深入研究。本论文主要取得了以下创新成果和研究进展： 1. 我们提出了用于光栅对调节的宽带光光谱图像法调节技术，依靠角锥、孔径光阑、针孔、光纤光谱仪和可调平面镜对实现光栅对的可视化调节，解决了将压缩器光栅精确地旋转至工作角度的技术难题。对空间啁啾进行了解析描述，揭示了空间啁啾会导致压缩脉宽的增加和焦斑直径的增大，从而降低了聚焦强度。基于现有的激光器参数，理论分析了激光系统剩余各阶色散量对压缩脉冲的影响，并且得到压缩器的最佳工作角度为52.87度。在空气压缩器中应用该调节技术，优化光栅对间距得到了比主光路更短的压缩脉冲和更为平坦的脉冲相位，在实验上证实了宽带光光谱图像法的有效性。建立了光线追迹数值模型，计算得到该调节方法的旋转角度精度、俯仰调节精度和面内旋转精度分别为±4.81 μrad、±7.92 μrad和±6 μrad。该技术还可用于水平转台绝对角度和相对角度测量校正。 2. 结合展宽器和光栅对压缩器，发展了激光系统中基于棱栅对(Grism pair)的色散精密控制技术。根据棱栅对三阶、二阶色散比值，设计了Grism pair的参数，并提出了Grism pair的远场调节方法。对SULF中10拍瓦钛宝石超强超短激光系统前端的材料色散进行了精密统计，给出了?ffner展宽器的参数设计和光学元件尺寸设计，并在理论和实验上研究了?ffner展宽器的输出光斑特性。同时研究了柱面?ffner展宽器的输出光斑特性。开展对比实验证明了Grism pair的色散精密控制与补偿能力，实验测得压缩脉冲的相位畸变小于2.25rad，宽度仅为傅里叶变换极限脉冲的1.04倍，100发次的压缩脉宽平均值为22.38 fs。同时发展了对向压缩器这种压缩器新构型，并在实验上证明了新构型的可行性。 3. 首次将棱栅对用于10拍瓦级钛宝石超强超短激光系统的色散精密控制。改进了棱栅对的优化方法，通过改变棱栅对的间距，配合调节压缩器的入射角度和斜距离实现高阶色散的控制。评估了放大过程中的非线性效应对脉冲光谱脉宽的影响。在激光系统放大能量为202.8焦耳时，压缩脉冲宽度为24 fs，获得了5.4拍瓦的激光输出，同时研究了大口径光斑的脉宽分布和时间稳定性。在增加一级钛宝石放大器获得339焦耳能量放大的情况下，获得了21飞秒的压缩脉冲，是目前同类型激光装置中最好的脉宽结果，能够支持10拍瓦级超强超短脉冲的放大输出，在工程上验证了色散控制技术的有效性。 4. 此外，本论文还深入研究了引入色散的三种机制：折射、衍射和干涉；比较了平行光栅对、棱镜对和展宽器等几何色散元件的结构和特点；全面掌握和消化了Matinez展宽器和?ffner展宽器的结构、光路和特点；研究了大口径压缩脉冲脉宽的测量技术等。; The development of ultraintense ultrashort lasers has created unprecedented extreme physical conditions for human beings in the laboratory scale, and has played a significant role in promoting the development of high-tech fields such as basic disciplines, cutting-edge interdisciplines, and light-material interactions. Based on chirped-pulse amplification (CPA) technique and its analog, optical parametric chirped-pulse amplification (OPCPA), the peak power that the laser system can generate is getting higher and higher, and the focusing power density is also getting stronger. At present, many countries and regions in the world, such as the European Union, France, and the United Kingdom, have invested heavily in the development of ultraintense ultrashort laser systems. One of the difficulties in building ultraintense ultrashort 10-petawatt laser systems is to precisely control the dispersion of the ultraintense laser system and eliminate the high-order dispersion of the system as much as possible, so that we can generate near Fourier-transform limited compression pulses, and achieve higher peak power at the same energy level. This paper is mainly based on the participation of the National Large Research Infrastructure, named Shanghai Superintense Ultrashort Laser Facility (SULF), with the development of the 10-pettawatt Ti: sapphire laser system. Based on the laser system, we have studied the dispersion generation mechanisms, commonly used dispersion elements and precision dispersion control technology of the laser system. The following innovations and research progress have been achieved in this thesis: 1. We propose a broadband spectrographic method for precision alignment of compression gratings, relying on a cube-corner prism, aperture diaphragms, pinholes, fiber spectrometers, and adjustable mirrors to achieve a visual adjustment of the grating pair. This method could be used to accurately rotate the grating to its working angle. Analytical description of spatial chirp reveals that spatial chirp leads to increases of the compressed pulse duration and the focal spot size, which reduces the focused intensity. Based on the current laser parameters, the influence of the remaining high-order dispersion of the laser system on the compression pulse is theoretically analyzed, and the optimal working angle of the compressor is 52.87o. This technique is applied in the air compressor, and a shorter compression pulse and a flatter pulse phase than the main laser beam is obtained by optimizing the grating distance. The effectiveness of our alignment method is confirmed experime- ntttally. A ray tracing model is also established, and the rotation angle accuracy, tip accuracy, and in-plane rotation accuracy are calculated to be ±4.81 μrad, ±7.92 μrad, and ±6 μrad, respectively. This technique can also be used for the correction and measurement of absolute angle and relative angle of turntables. 2. Combining with the stretcher and grating compressor, the technique of precision dispersion control of the laser system is developed. Based on the ratio of the third-order and second-order dispersion of the grisms, the parameters of the grism pair are designed, and the far-field adjustment method of the grism pair is proposed. Precise statistics of the material dispersion of the front end of SULF is given. The parameters design of the ?ffner stretcher and the dimension design of the optical elements are also given. The output spot profile of ?ffner stretcher is studied theoretically and experimentally. At the same time, we have studied the output spot characteristics of the cylindrical ?ffner stretcher. The contrast experiment proves the precision dispersion control and compensation capability of the grism pair. The measured phase distortion of the compressed pulse is less than 2.25 rad, the pulse duration is only 1.04 times that of the Fourier- transform limited pulse, and the average value of the compressed pulse duration for 100 shots is 22.38 fs. Meanwhile, a new configuration of bidirectional compressor is developed, and the feasibility of the new configuration is proved experimentally. 3. For the first time, the grism pair is used for precision dispersion control of the 10-petawatt-class Ti: sapphire superintense ultrashort laser system. The optimization method of the grism pair is improved. By changing the grism distance, and the incident angle and the distance of the compressor, the higher-order dispersion can be realized. The effects of nonlinear effects in the amplification process on the pulse duration and pulse spectrum are evaluated. When the pulse energy is amplified to 202.8 Joules, and the compressed pulse duration is 24 fs, an output of 5.4 PW is obtained. The pulse duration distribution and time stability of the large-aperture laser beam are also studied. In the case of adding another Ti: sapphire amplifier, the laser energy is amplified to 339 J, we have succeeded in obtaining 21 fs compressed pulses, which is the shortest pulse duration in the same type of laser facility till now. It can support 10 PW ultrashort laser pulses. As a result, the technique of dispersion control has been verified in engineering. 4. In addition, we have also deeply studied three mechanisms of dispersion generation: refraction, diffraction and interference; compared the layout and characteristics of geometric dispersion elements such as parallel grating compressors, prism pairs and stretchers; fully comprared the layout and characteristics of Matinez stretcher and the ?ffner stretcher; the measurement techniques of pulse durations for large-aperture beams are studied. |
| 学科主题 | 光学 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/31120]  |
| 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 | 李帅. 钛宝石超强超短激光系统色散精密控制技术研究[D]. |
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