神光Ⅱ大型固体高功率激光装置是我国激光驱动器发展历史的里程碑, 其成功研制使我国高功率固体激光工程与技术、聚变物理与基础物理研究实现了全面且本质的跨越式发展。简要概述了神光Ⅱ激光装置研制中创新发展的大量工程方案与技术手段, 举例介绍了神光Ⅱ激光装置在近20年来的高质量运行中取得的众多有国际影响力的研究成果。经多方支持和多年持续发展, 已经形成数万焦耳级纳秒激光装置、皮秒拍瓦以及飞秒拍瓦激光装置等, 这些装置是我国惯性约束核聚变、强场物理、高能量密度物理等研究领域中重要的物理实验核心平台之一。

A theoretical calculation is presented for third-harmonic generation in KDP crystal for type Ⅱ- type Ⅱ polarization-mismatch scheme by using the four-stepped Runge-Kutta method. For the “Shenguang Ⅱ” frequency tripling system, the doubling angle θd and the tripling angle θt are located at optimized situation, by changing detuned values of the polarization angle θp, the corresponding changes of pulse shape properties was gotten. The results show that when the polarization angle θp is located at optimized situation, the full width at half maximum (FWHM) τ is minimum and the pulse shape rises fastest. Increasing the θp from optimized situation causes the τ widens faster and the pulse shape rises slower than decreasing the θp from optimized situation. In the experiment, by changing the polarization angle θp, the pulse shapes consistency of the “Shenguang Ⅱ” eight frequency tripling beams has been accomplished. This work offers a method for adjusting crystals and actualizing power balance.

使用四阶龙格-库塔算法数值求解Ⅱ类-Ⅱ类偏振失配方案的三倍频稳态耦合波方程组。针对“神光Ⅱ”激光驱动器的三倍频系统，在二倍频匹配角θd和三倍频匹配角θt均处于最佳匹配情况下，以1°为单位改变偏振分配角θp的偏离量，得到对应的三倍频波形特性的变化。研究表明，偏振分配角θp处于最佳理论匹配位时，对应的三倍频波形半峰全宽最窄，且波形上升沿抬起也最快; θp从最佳匹配位增加比从最佳匹配位减小对应的半峰全宽变宽更快，对应的上升沿抬起更慢。根据所得理论结果，在实验中调节偏振分配角θp,达到了改变三倍频输出波形特性，进而实现八路三倍频波形一致的目的。该研究结果对于更快地实现激光驱动器装置的功率平衡有一定的应用价值。

The "Shenguang-II" Facility laser uses an 8-beam double-pass architecture capable of delivering several KJ of infrared or ultraviolet energy in a temporal pulse format of an approximately 1ns quasi-square. Ideally the output wavefront of each beam from the main spatial filter should be a plane wave. But a real output wavefront of the laser light beam with a 200 mm section diameter in our facility is always a complex superimposed one. On its cross section, it has a distribution of curvature radius, which is called "local curvature radius" here. But the quality level of the output wavefront is mainly marked by its "global curvature radius", which is an assessing result based on the local ones. To meet the requirements of enhancing the conversion efficiency of the KDP crystal, each beam of wavefront out of the main spatial filter should resemble a plane wave as possibly as it can. Because only in this way can we achieve an optimal match between the injection direction of the laser beam and the functioning angle of the KDP crystal. In other words, the global curvature radius of each beam wavefront should be as large as possible. We have assessed the global curvature radiuses of eight beams, wavefronts by measuring their local curvature radii using Hartmann method. Finally, we have acquired better frequency conversion efficiencies by correcting each output wavefront to a better level according to the measurement results.

This paper discusses a method of characterizing the gain of the laser pulse amplifier using its gain fluence curves and studies gain fluence Curves of a single amplifier．These help US to understand the characteristics of the amplifier and provide a powerful tool for the investigation of the power balance．

For precision SG-Ⅱ power balance, there must have same output energy and output pulse waveform in the 8 beams, it means that the gain and transmissivity in every amplifier chain are same. But the gain abilities of the same type amplifiers in 8 beams are different for needing of daily operation. It was a first time that small signal gain of different amplifiers in SG-Ⅱ were measured online by using a small energy measurement system which has superior 1% precision. The small signal gain values of 40 and 70 rod amplifiers, 100 slab amplifiers and 200 double slab amplifiers are got in the regular working voltages. The differences of the same type amplifiers are quantized and that provides valuable experimental data to power balance in SG-Ⅱ precision.

Power balance between laser beams is important for high-power laser system. This paper uses a calculation method as an exact solution for laser amplification to simulate the output pulse shape of “Shenguang Ⅱ" laser facility. The results are preferable,as compared with the results of the experiments.

神光Ⅱ装置精密化功率平衡要求8路子光束的输出能量平衡和脉冲波形一致,即每条放大链的增益和透过率相同。但装置因日常打靶工作需要,8路子光束放大链中同级放大器的增益能力差异较大。针对该问题,利用一种精度优于1%的小能量测量系统,对神光Ⅱ装置8路四级放大器的小信号增益进行在线测量,分别得到了40,70棒状放大器,100片状放大器和200双层片状放大器在正常工作电压下的小信号增益值,掌握了每路各级放大器的增益特性,精确量化了各路同级放大器的差异,为神光Ⅱ精密化功率平衡调试提供了宝贵的实验数据。

With the aim of achieving the power balance of “SHENGUANG Ⅱ”, the innovative project of the main array amplifier with the angular variable mirror is studied. The first engineering research results of the new project which were attained on “SHENGUANG Ⅱ” are reported in this paper, including the project design essentials, the outcome of the performance measurement and check in- line, and the result of general energy balance experiment.

为了实现神光Ⅱ装置的功率平衡，研究了在组合主放大器中插入角变反镜的新方案。报道了新方案在神光Ⅱ装置上获得的工程研究结果，包括方案设计要点、在线性能测量与考核以及能量平衡总体实验结果。