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高功率激光装置三倍频脉冲特性精密诊断技术及高效谐波转换方法研究
其他题名Studies on 3ω Precision Diagnosis Technology and High Efficient Harmonic Conversion of High Power Laser Facility
刘崇
学位类型博士
导师林尊琪
2016
学位授予单位中国科学院上海光学精密机械研究所
关键词惯性约束聚变 高功率激光装置 3?精密诊断系统 非共线ii类和频 超短脉冲测量
摘要高功率激光驱动器是实现惯性约束聚变的重要技术手段之一。经过近半个世纪的发展,激光聚变技术对驱动器输出能力的要求也不断提高。目前,美国国家点火装置的峰值输出功率已达500TW。随着输出能力的不断提高, 脉冲导致的光学元件激光损伤也日趋严重,并逐渐成为影响驱动器整体负载能力以及远场聚焦能力的主要技术障碍。从事高功率激光装置的科研人员迫切需要了解 激光脉冲的各项参数,如近远场、时间波形、光谱、能量以及超短脉冲的光谱及相位信息, 激光参数测量技术因此得到迅速的发展,并达到精密化的程度。本文系统的介绍了国内外高功率激光装置的输出能力及其 参数精密诊断工作的发展过程及现状,以“神光II”升级驱动器为平台,详细阐述了“神光II”升级驱动器 参数诊断系统样机的研制与实验过程,并进一步提出了一种基于KDP晶体非共线和频技术的新型终端光学系统设计构想。最后简要叙述了超短脉冲测量技术的时频分析特性与近期发展方向。 第一部分介绍了国内外ICF装置发展现状与相应的 参数测量工作进展。指出1996年,Beamlet装置出现了较为严重的大口径石英元件损伤问题,因此LLNL实验室开始致力于 焦平面诊断系统(FPD)的研制。这一时期,主要功能是实现 脉冲70μm近场分辨率测试,以满足对小尺度自聚焦现象的有效监测。2007年,美国国家点火装置(NIF)研发了 综合参数精密诊断系统(PDS),为满足点火以及各种精密物理的实验要求,这一阶段的测试系统引入了高精度脉冲波形及精密光谱测试功能,并将 远场品质因子提高到近理论极限的水平,各项测试功能均已达到精密诊断的要求,为NIF实现192路激光 能量1.8MJ 输出做出了重要贡献,也为“神光II”升级驱动器 参数测量系统设计与研制提供了重要的参考与借鉴。 第二部分以“神光II”升级驱动器为平台,介绍了“神光II”升级驱动器 参数诊断工作的进展情况。目前,“神光II”升级驱动器终端光学系统大口径石英元件同样存在着 激光损伤以及损伤增长问题。同时 远场焦斑以及SSD焦斑特性作为表征激光器性能的重要参数,也急需对其进行评估。本节详细介绍了“神光II”升级驱动器 精密诊断系统样机的设计、调试、首轮实验以及后续改进计划:为得到较为可靠的远场焦斑测量结果,焦斑成像系统应具备较宽的成像视场和成像空间,以便满足光路调试的容许误差。基于上述要求,利用三级像差理论分析了椭球面以及离轴球面三反类Cassegrain系统的像差特性,最终选用与NIF的PDS装置类似的球面三反类Cassegrain系统作为“神光II”升级驱动器 精密诊断系统的成像系统。首轮实验获得了“神光II”升级驱动器半极限输出状态下的近远场以及SSD焦斑的有效测量数据,但能量、光谱以及时间波形测量功能还有待改进。 第三部分介绍了基于KDP晶体非共线和频方案的新型终端光学系统设计方案构想。国内外目前比较成熟的终端光学系统均采用楔形透镜作为聚焦与色分离原件。随着 激光峰值功率的不断提高,石英元件的损伤也越来越明显,严重影响 远场可聚焦能力的提升。并且非对称聚焦系统给调靶过程带来了诸多不便,需要引入包括4D干涉仪在内等一些列复杂技术手段。因此本节提出了一种利用KDP晶体的非共线II类和频方案,利用弯月透镜即可实现远场色分离,并取得了较好的实验效果,为终端光学系统的改进提供了一种可行的方案。 第四部分简要介绍了上世纪90年代后期陆续出现的几种超短脉冲全信息测量方法。从时频分析的角度归纳总结了这几种方法的共性,肯定了非线性过程在超短脉冲全信息测量工作中的必要性。着重分析了FROG超光谱仪分辨力现象的模拟结果与原因。并指出分辨极复杂脉冲的光谱精细结构、扩展时间窗口并将FROG引入ps甚至ns脉冲的测量领域是近年来FROG的发展方向。
其他摘要High power laser facility is one of the reliable means for Inertial Confinement Fusion(ICF). Through half a century development, ICF puts forward more and ever higher request on high power laser facility. As a result, the output power and energy improves rapidly. In this period, the parameters of pulse are very desired for researchers engaged in laser for ICF, for example, far field, near field, spectrum of SSD beam, energy and temporal waveform, et al.Consequently, the measuring of beam parameters is developed as a key technique in ICF. In this paper, the development history of high power laser and the corresponding parameter diagnostic technique at home and abroad are introduced firstly. Then, the progress of precision diagnostic system prototype and the improvement scheme of Final Optical Assembly(FOA) of SGII-Updated Facility are detailed. Finally, the time-frequency characteristics and development trend of ultrashort pulse measuring method is analyzed. In section 1, Inertial Confinement Fusion and precision diagnostic technique is detailed. Take NIF (National Ignition Facility) as an example, the accuracy of Precision Dianostic System (PDS) has reached the level of theoretical limit by 2007, which makes a significant contribution to the output capability of 1.8MJ at in 2009. In section 2, the progress of precision diagnostic system prototype of SGII-Updated Facinity is introduced. In this part, design, install, first experiment, deficiencies and improvement scheme are discussed: aberration characteristic of ellipsoidal surface and off-axis spherical Cassegrain system are analyzed by third-order aberration theory. And off-axis spherical Cassegrain system is selected finally. In first experiment, far field, near field and SSD spot of in the state of half ultimate output capacity of facility are obtained veritably by precision diagnostic system prototype, but the measurement functions of energy, spectrum of SSD pulse and time waveform of pulse require improvement in future. In section 3, improvement scheme of the FOA’s structure based on II type noncollinear SFG is discussed. At home and abroad, wedged lens is usually used as the focusing and color separation units of FOA. As the development of peak power of pulse, laser damage of silica elements is more obviously. This problem has caused serious impact on focusing power of beam. Another defect of wedged lens is that it complicates the procedure of collimation of target and focus spot of FOA,in which procedure a series of complicated technical means must be used, such as 4D interferometer. In this section, an improvement program of FOA based on II type noncollinear SFG is proposed, in which the color separation in far field canbe realized by meniscus lens. This program is confirmed by an experiment using 50×50mm2 KDP crystal. In section 4, several measurement method of ultrashort characteristic which appear from the 90's to present are introduced. The generality of measurement method which can obtain the spectral phase of ultrashort is summarized using the theory of time-frequency analysis. Consequently, the necessity of nonlinear process in ultrashort characteristics is obviously. And the phenomenon which indicates that FROG can obtain the fine structure of spectrum of extremely complex pulse that will be lost by direct measurement using spectrometer is simulated by MATLAB and discussed. Obtaining the fine structure and extending the measurement window using high dispersion element is the trend in development of FROG currently, for the purpose of introducing FROG in ps and ns pulse characteristics.
语种中文
文献类型学位论文
条目标识符http://ir.siom.ac.cn/handle/181231/15952
专题学位论文
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GB/T 7714
刘崇. 高功率激光装置三倍频脉冲特性精密诊断技术及高效谐波转换方法研究[D]. 中国科学院上海光学精密机械研究所,2016.
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