研究了薄片激光器中晶体与热沉的封装技术和核心技术，采用薄片晶体与金刚石热沉的光胶工艺，自主设计并研制了5 mm口径的YAG/Yb∶YAG复合薄片激光模块，分析了该薄片激光模块的多通泵浦系统，建立了晶体热效应数值仿真模型，实验测量了在2.2 kW/cm²泵浦功率密度、940 nm泵浦波长下薄片晶体的热焦距为445.6 mm；采用基于光胶工艺封装的薄片激光模块搭建连续激光器，在70 W泵浦功率下获得了18.75 W功率的基横模输出，斜率效率和光光转换效率分别为36.59%和26.79%。

薄片激光器可以实现高峰值功率、高平均功率、高光束质量的激光输出，是高重复频率皮秒泵浦源的关键技术之一。基于Yb∶YAG单薄片激光模块设计并搭建了再生放大系统，连续泵浦下获得了平均功率为40.9 W、重复频率为1 kHz、脉冲宽度为3.4 ns的激光输出，水平方向上的光束质量因子（Mx2）和竖直方向上的光束质量因子（My2）分别为1.12和1.10。基于腔内光束指向主动控制技术，2 h输出的平均功率稳定性峰谷（PV）值和均方根（RMS）值分别为6.42%和0.56%。在600 μs脉冲泵浦情形下，光光效率达16.1%。在10 kHz重复频率下，获得了53.3 W的高平均功率的激光输出，Mx2和My2分别为1.07和1.06。

采用光强度调制鉴相方案,使用直接数字频率合成器(DDS)和激光驱动器产生频率稳定的调制激光,注入待测光路,在待测光路后进行光电转换和放大,引入参考本振信号作为混频器相位参考信号,利用混频器测量待测光路信号与参考本振信号的相位差,获得光路延时信息。主要特点如下:提出了在本振信号链路三段移相的差分式检测方法,优化了鉴相点,提高了测量精度;采用单段短时两相位点测量模式,有效降低了光源功率波动、光路中光强波动、光电探测及放大电路增益波动、温度变化导致相位差漂移等带来的测量误差;在每个相位点多次测量采样,根据测量的平均值计算相位差,推导时间差。详细分析了测量电压和被测时延之间的函数关系,分析了影响测量精度的因素,构建验证系统,完成了实验验证。实验结果表明:本方案在4 ns的时延内的测量精度可达1 ps,大幅提升了现有高功率激光装置的同步测量精度。

搭建了一台中等重复频率、高峰值功率的Nd∶YAG激光器。激光器主要包括三部分：单纵模全光纤种子源、LD抽运的Nd∶YAG再生放大器和氙灯抽运的Nd∶YAG功率放大器。该系统获得了平均功率为12 W、重复频率为10 Hz、单脉冲能量为1.2 J、脉冲宽度为3 ns的激光输出, 工作波长为1064 nm, 输出光束口径为10 mm, 95%的能量在600 μrad范围内, 近场光强近平顶分布, 近场光强调制度小于1.2, 时间波形近似方波, 能量稳定性均方根值小于1.4%。

Aiming at morphology of laser induced damage mitigation pit on the rear surface of 3ω silica optical component, the mitigated area and its downstream intensity distributions with different morphologies are simulated by finite-difference time-domain method (FDTD) and Rayleigh-Sommerfeld (R-S) diffraction integral method, respectively. The results show that when the angle between the tangent line of endpoints on the section contour of the pit and incident light is over 70°, the maximum intensity inside the mitigated optics is less than 1.66, and mitigation effect is better than that of other angles. The maximum downstream intensities of a pit in shape of parabolic surface, cone and truncated cone are all less than 1.46 with an angle of 70° and a width of 200 μm. But when the width of pit increases to 1 mm, for instance, the maximum downstream intensity is as high as 9.31 and area with high intensity covers a long range. Thus, taking the difficulty of laser machining technology into account, a conical pit with an angle larger than 70° is the first choice for the damage mitigation on the rear surface of silica optical component.

提出应用于神光Ⅱ装置中的拍瓦短脉冲与主压缩脉冲高精度同步方案。在该方案中，通过与门技术实现了锁模激光器输出的短脉冲序列与主激光总控触发信号时间的初步锁定，该技术是实现惯性约束核聚变高功率激光装置中长短脉冲精确同步的关键。由总控系统的触发信号作为与门中可编程现场门阵列(FPGA)电路的触发信号，锁模激光器输出的百皮秒激光脉冲通过光电转换放大,并由同步展宽装置进行处理之后，作为FPGA电路的时钟信号，能够实现系统主激光门脉冲触发信号与短脉冲激光之间均方根值为26.3 ps的同步精度，这一技术可有效提升装置中同步系统的稳定性。

针对三倍频光学元件后表面的损伤修复形貌，分别采用时域有限差分法（FDTD）和瑞利索末菲（R-S）衍射积分法，来模拟不同形貌下元件修复区域内以及其后续的光场分布。结果表明，当修复坑截面轮廓线端点切线与光束传播方向夹角大于70°时，元件内部光强极大值小于1.66，修复效果优于其他角度。夹角为70°、宽200 μm的抛物面型、圆锥型和圆台型凹坑的后续光强极大值小于1.46。但是当修复坑宽度较大如达到1 mm时，圆台型凹坑的后续光强极大值高达9.31，且作用区间长。因此，考虑实际激光修复工艺的难度，夹角大于70°的圆锥型凹坑是石英元件后表面损伤修复的首选形貌。

Electric field distribution, in the wavelength range 1053 nm and 0° high reflection coatings, with different truncated conical pits has been estimated by using the finite difference time domain method (FDTD). Results of simulations indicate that the smaller the angle between the pit’s edge and the normal line, the higher the damage threshold of the mitigation pit. In the experimental process, the dimension of this angle mainly depends on two factors, i.e. the influencing area of the focal spot and the depth of mitigation pits. Because the ratio between them is the angle’s tangent, decreasing the influencing area of the focal spot and increasing the depth of the machined area could yield a mitigation pit with a smaller angle. By optimizing the focal spot size, pulse energy, step size and the number of machining passes of femtosecond laser micromachining, a pit with an angle of 25° and a depth of 14 μm is obtained. The typical damage threshold of the mitigation pit is about 21 J/cm2, which is 2.3 times greater than the fluence-limited defect. Moreover, the laser damage testing results of 50 mitigation pits show that the mitigation process has a good repeatability. The correlation between the cone angle and the damage threshold is also examined, the simulations are in agreement with the experimental results. The ratio of the maximum intensification between 45° and 25° cone angles is ~2.5 and that of the damage threshold between the two angles is 0.5. At the same time, the relationship between the micromachining pulse width and the damage threshold is also estimated: if other process parameters are kept constant, a longer pulse length tends to produce lower laser-resistant mitigation pits. Compared to the result of 260 fs laser pulse, the truncated conical pit created by 6 ps laser pulse has a smaller depth, which implies that more thermal effect occurs during the miromachining process. However, cracks are not found around the pit. Thus, thermal damage is not the major reason for the decrease of damage threshold. Meanwhile, smaller depth also indicates that the pit has a large cone angle. According to the result of former FDTD simulation, the decrease of damage threshold is mainly caused by electric field enhancement in a pit with a large cone angle.