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chi20191126上海光机所梁晓燕557647After decades of development, ultra-intense and ultra-short laser technology has reached to the order of 10 Petawatt. The peak intensity is one of the key parameters in ultra-intense and ultra-short laser applications. With the improving of the focusing method, the peak intensity of petawatt-class ultra-intense and ultra-short laser systems can reach to ~1022 W/cm2. It provides an extreme physical condition for studying the interaction between laser and matter, which makes it enter the field of relativistic optics, and greatly promotes the development of frontier disciplines including plasma physics, particle acceleration, proton imaging and attosecond optics. With advances in physical experiments such as quantum effect and quantum electrodynamics, higher focal intensities are required. At present, a number of laboratories in the world are developing and constructing multi petawatt-class ultra-intense and ultra-short laser devices, and by improving the focusing ability of the laser devices to achieve a higher focal intensity. Based on the Shanghai Ultrafast Laser Facility SULF-10 PW which is built by Shanghai Institute of Optics and Fine Mechanics, the evolution of wavefront phase in the SULF-10 PW laser system was measured and a scheme for improving the focusing performance of the multi petawatt-class ultra-intense and ultra-short laser device is proposed in this paper from the analysis of the main amplifier in the system. After the correction and optimization of the wavefront, a peak intensity of 2 × 1022 W/cm2 is achieved in the SULF laser system. The main results in this paper are as follows: 1.The evolution of wavefront phase of signal light under static state was measured step by step in the SULF laser system at 5.4 PW output condition. By analyzing the evolution of the wavefront in the laser transmission process, the influence of the traditional mechanical stress, spatial propagation and spatial distortion of the compressor on the wavefront phase of the beam in the system was excluded. It is determined that most of the static wavefront distortion of laser beam comes from the accumulation of surface distortion of optical elements, and the layout of the adaptive optical systems in the laser device were determined. 2.Study the influence of single chirped pulse amplification on signal wavefront in SULF laser system. The experimental results show that the pump light wavefront has little influence on the wavefront change of the signal light. It is also shown that the parasitic oscillations and thermal effects that may occur during the single amplification of Ti: S do not significantly affect the dynamic wavefront of the signal light, which provides technical support for the wavefront correction and the measurement scheme of the focal spot. 3.The method of two cascaded DMs with different actuator densities based on focus feedback corrected the wavefront aberrations of the signal successfully in the SULF laser system at 5.4 PW output condition. The beam aberrations near the focal spot are corrected from 0.556 μm to 0.041μm. The corrected beam is focused by an f/2.5 off-axis parabolic mirror (OAP),and the size of the focal spot is 2.75 × 2.87 μm2 (FWHM), and a peak intensity of 2 × 1022 W/cm2 is achieved. 4.For the SULF-10 PW repeat frequency laser system currently under construction, the wavefront phase information of each key point in the system was measured step by step, which provided support for the current amplification and compression and ensured the wavefront correction and focusing of the later system in the future. 5.Preliminarily explore the new combined focusing mode of off-axis parabolic mirror and ellipsoid mirror. Based on the low-power continuous laser source, the combined structure can reduce the focal spot from 15.5 μm to 7.38 μm (FWHM), which is consistent with the simulation results. It provides an experimental basis for the subsequent application of SULF-10 PW laser system to further enhance the focusing intensity.2020atalunwen2211315521514Petawatt laser system; Wavefront distortion; Adaptive optics;Wavefront correction; FocusingStudy on the focusing ability for petawatt-level laser system数拍瓦超高功率激光系统聚焦性能研究超强超短激光技术经过几十年的发展,峰值功率已经达到了10拍瓦量级。而聚焦峰值功率密度是超强超短激光应用中的关键参数之一。随着聚焦技术的不断发展,超强超短激光装置的聚焦峰值功率密度已经可以达到1022W/cm2,这为研究激光和物质相互作用提供了极端物理条件,使其进入了相对论光学领域,极大促进了包括粒子加速、质子成像和阿秒光学等前沿学科的发展。而为了探究量子效应和量子电动力学等更多未知的领域,物理学家对聚焦峰值功率密度提出了更高的要求。目前,世界上有多个实验室正在研制和建设数拍瓦级超高功率激光装置,并通过提升超强超短激光装置的聚焦性能以达到更高聚焦强度的目的。 本文基于上海光机所研制的上海超强超短激光实验装置SULF-10 PW,通过对SULF-10 PW激光系统波前畸变进行测量和研究,分析经过各个关键节点波前畸变的起因及演变规律,提出提升SULF激光装置在数拍瓦工作状态下聚焦性能的方案,并通过波前校正和优化,成功在5.4 PW的基础上实现了2 × 1022 W/cm2的聚焦强度输出。具体工作内容为: 1.基于SULF激光装置在5.4 PW输出条件下,逐级测量了静态条件下信号光的波前相位演化,通过分析激光传输过程中波前参数的演变规律,排查了系统中传统机械应力、空间传播和压缩器角色散对光束波前相位带来的影响,确定了激光光束的静态波前畸变规律,并确定了自适应光学系统在激光装置中的布局。 2.研究了SULF激光装置单次啁啾脉冲放大过程对信号光波前的影响。实验研究表明,钛宝石单次放大过程中泵浦光的空间波前畸变对放大信号光的相位畸变几乎不产生影响,同时可能出现的寄生振荡和热效应等问题对信号光的动态波前也不会产生明显影响,为后期波前校正系统和聚焦焦斑测量方案奠定了技术支持。 3.基于焦点反馈的不同电极密度双变形镜级联校正方法,对高、低级畸变分别补偿,成功对5.4 PW激光的波前畸变实现校正,将该系统的波前畸变RMS值0.556 μm优化为0.041μm,利用F#2.5的OAP聚焦后,得到了半高全宽为2.75×2.87 μm2、接近衍射极限的焦点。系统的聚焦峰值功率密度达到了2 × 1022 W/cm2,极大提升了激光系统的聚焦能力。 4.针对在建的SULF-10 PW重频激光系统,逐级测量了系统中各关键节点的波前相位信息,为目前正在进行的放大压缩工作提供了支持,并为后期系统的波前校正和聚焦提供了保障。 5.初步探究离轴抛物面镜和椭球镜的新型组合聚焦方式,基于基于小功率连续入射光源,组合式结构将聚焦光斑(半高全宽)从15.5 μm降到7.38 μm,与模拟结果吻合,为后续应用于SULF-10 PW重频激光装置,进一步提升聚焦强度提供了实验基础。拍瓦级激光系统;波前畸变;自适应光学;波前校正;聚焦中国科学院上海光学精密机械研究所郭震光学工程博士
中文题目: 数拍瓦超高功率激光系统聚焦性能研究
外文题目: Study on the focusing ability for petawatt-level laser system
作者: 郭震
导师姓名: 梁晓燕
学位授予机构: 中国科学院上海光学精密机械研究所
答辩时间: 20191126
中文关键词:
拍瓦级激光系统;波前畸变;自适应光学;波前校正;聚焦
英文关键词:
Petawatt laser system; Wavefront distortion; Adaptive optics;Wavefront correction; Focusing
中文摘要:
英文摘要:
文献类型:学位论文
学位级别: 博士
正文语种: chi
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