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。

为提高自动准直效率, 结合以太网, 设计出一套新型光路自动准直控制和检测方案.该方案采用基于耦合矩阵的前馈补偿及图像Jacobian矩阵的近远场串并行准直方式, 并引入局部自适应阈值和二值化算法, 同时将模糊控制算法运用到步进电机的调整过程中, 提高光束近远场图像的处理精度, 降低系统的准直时间.实验结果表明, 该准直系统远场的平均调整误差为空间滤波器小孔直径0.44%, 能够满足准直系统远场调整精度(小于小孔直径5%)的要求, 准直时间由原有的30 mins缩短至12 mins左右.

提出应用于激光脉冲高精度时间同步测量的技术方案。利用时间数字转换技术, 精确测量激光脉冲相对延时, 测量精度可小于10 ps(峰谷值)。为满足测量电路对脉冲宽度的要求, 设计针对短脉冲激光的电脉冲展宽模块, 可以将百皮秒量级的电脉冲展宽至纳秒量级, 引入时间抖动的均方根值小于2 ps。该测量方案实现了实时高精度时间同步测量, 可以作为时间同步反馈补偿的实时监测使用。

设计了一款应用于无源光网络(PON)的突发模式激光驱动器及其双环功率控制电路。提出一种电荷补偿和动态偏置电路, 减小了激光驱动器电流上升和下降时间, 提高了输出电流能力; 提出一种双环功率控制的反馈电路, 解决了平均功率和消光比随温度变化的问题。基于0.18 ?滋m RF CMOS工艺完成流片, 激光驱动器芯片面积为1 600 ?滋m×800 ?滋m。测试结果表明, 激光驱动器的输出偏置电流和调制电流分别可达90 mA。激光驱动器突发响应开启时间小于2 ns, 关断时间小于1 ns, 发送数据速率高达2.5 Gbit/s, 抖动大小为41 ps。激光驱动器输出平均光功率稳定性为±0.26 dB, 消光比稳定性为±1 dB。该激光驱动器满足了PON系统对激光器的输出功率和稳定性要求。

采用相位调制技术产生的具有一定光谱分布的相位调制脉冲可以有效抑制高功率激光驱动器中大口径光学元件的横向受激布里渊散射和满足光束匀滑需求, 但该脉冲在装置各系统传输放大过程中, 由于光谱畸变会引起幅频调制(FM-to-AM)效应, 这种效应严重影响了激光装置的输出性能及实验效果。介绍了相位调制脉冲产生原理、引起FM-to-AM效应的根本原因及因素, 综述了目前美国的国家点火装置、法国的兆焦耳装置以及我国的神光-Ⅲ主机装置在FM-to-AM效应抑制技术方面取得的重要进展。

To overcome the problem of cleanliness in the laser′s internal cavity, a glass cavity design for a Nd: glass slab amplifier was proposed, which uses UV-stop quartz glass for its main structure.The design of the main structure of the glass cavity and the sealing are optimized, and metal-coated surfaces are used to prevent light from escaping.The cleanliness of the stainless steel cavity of the slab amplifier of the SG-II-UP laser and the glass cavity of a 100 slab amplifier were compared; the cleanliness of the glass cavity was found to be 70% better than that of the stainless cavity. Further, advanced system analysis program was used to simulate the designed amplifier, with the pumping ratio of the Nd: glass in the glass cavity being increased by 8.84%.Thus, the glass cavity decreases the production of aerosols and enhances the pumping ratio of the Nd∶glass.

To overcome the problem of cleanliness in the laser′s internal cavity, a glass cavity design for a Nd: glass slab amplifier was proposed, which uses UV-stop quartz glass for its main structure.The design of the main structure of the glass cavity and the sealing are optimized, and metal-coated surfaces are used to prevent light from escaping.The cleanliness of the stainless steel cavity of the slab amplifier of the SG-II-UP laser and the glass cavity of a 100 slab amplifier were compared; the cleanliness of the glass cavity was found to be 70% better than that of the stainless cavity. Further, advanced system analysis program was used to simulate the designed amplifier, with the pumping ratio of the Nd: glass in the glass cavity being increased by 8.84%.Thus, the glass cavity decreases the production of aerosols and enhances the pumping ratio of the Nd∶glass.

The prompt pump-induced wavefront characteristic of high power laser facility is undertaken to address an important aspect of the wavefront control system for the high power laser facility. Based on the ShenGuang Ⅱ four-pass amplification high power laser facility (SG-Ⅱ-FAF), numerical simulation is conducted on the prompt pump-induced wavefront distortion through ANSYS and Matlab. In order to obtain the space-time characteristics and variation features, the Hartmann wavefront analyzer is employed to conduct experiments on prompt pump-induced wavefront distortion and thermal wavefront recovery aberration after xenon lamp pumping. The numerical simulation results agree well with experimental results. The prompt pump-induced wavefront distortion of single-slab-amplifier is about 0.12λ (wavelength λ=1053 nm) of peak-to-valley (PV), and the whole optical wavefront of the SG-Ⅱ-FAF is about 5λ of PV with different laser beams, whose shape looks like a “saddle”. Simulations and experiments provide important data for the wavefront control system of SG-Ⅱ-FAF, emission laser passing through the space filters sucessfully and pumping uniformity of slab Ndglass amplifier. As a result, the far-field focus spot energy concentration of the laser beam is improved, meanwhile the success rate and the working efficiency of the SG-Ⅱ-FAF operational experiment are increased.

高功率激光驱动器动态波前特征及其规律是激光驱动器光束波前质量控制关键研究内容之一。以神光Ⅱ四程放大高功率激光驱动器为研究平台，使用ANSYS和Matlab对激光驱动器瞬时动态波前进行了模拟计算，并利用哈特曼波前分析仪对驱动器氙灯抽运引入的瞬时动态像差和热恢复像差进行了实验研究，得到其时空特性和变化规律。理论模拟和实验结果具有一致性，单片片状放大器动态像差峰谷(PV)值约为0.12λ (波长λ=1053 nm)，驱动器总体瞬时动态像差PV值约为5λ ，呈“瓦片”形态。模拟计算和实验分析为神光Ⅱ四程放大高功率激光驱动器光束波前质量控制、激光发射顺利通过空间滤波器和片状放大器抽运均匀性优化等提供了重要的参考数据，提升了输出光束远场焦斑能量集中度，提高了驱动器激光发射的成功率和运行效率。