时间分辨的泵浦探测技术是研究光学元件损伤动态过程的有力手段。基于增强电荷耦合器件（ICCD）的时间分辨泵浦探测技术，对比研究了1064 nm纳秒激光辐照下HfO₂/SiO₂增透膜膜面处于激光入射面（正向过程）和出射面（反向过程）两种情况下的动态损伤过程。在同一能量密度（52 J/cm²）激光辐照下，正向和反向过程都产生了无膜层剥落的小坑损伤以及伴随膜层剥落的小坑损伤，但反向过程产生的小坑的横向尺寸和深度都比正向的大。有限元分析结果表明正向和反向过程中增透膜内部的基底-膜层界面场强相似，但实际损伤形貌尺寸以及依据冲击波传播速度计算得到的爆炸能量都表明反向过程沉积的能量更大，可见等离子体形成后在后续激光脉冲辐照下的发展过程决定了两种情况下的损伤差异。增透膜损伤的时间分辨研究对其损伤机制分析以及实际应用具有重要意义。

研究了用于三倍混频的Ⅱ类DKDP晶体在35 ps，850 ps和7.6 ns三种不同脉宽355 nm波长激光作用下的损伤特性。实验对比分析了损伤阈值、概率和损伤针点形貌、尺寸和密度，并根据损伤阈值及概率得到前驱体阈值及密度。结果表明，前驱体的激光能量吸收量与脉宽线性相关。35 ps激光作用下DKDP有一种前驱体吸收激光能量形成熔融状损伤针点。850 ps激光作用下有两种前驱体吸收激光能量并产生力学破坏形成中心熔融四周断裂的损伤针点。7.6 ns激光作用下只有一种前驱体吸收激光能量，并且形成的损伤针点与850 ps对应的损伤针点有相同特征。

Plasma scalding is one of the most typical laser damage morphologies induced by a nanosecond laser with a wavelength of 1053nm in HfO₂=SiO₂ multilayer films. In this paper, the characteristics of plasma scalds are systematically investigated with multiple methods. The scalding behaves as surface discoloration under a microscope. The shape is nearly circular when the laser incidence angle is close to normal incidence and is elliptical at oblique incidence. The nodular-ejection pit is in the center of the scalding region when the laser irradiates at the incidence angle close to normal incidence and in the right of the scalding region when the laser irradiates from left to right at oblique incidence. The maximum damage size of the scalding increases with laser energy. The edge of the scalding is high compared with the unirradiated film surface, and the region tending to the center is concave. Plasma scald is proved to be surface damage. The maximum depth of a scald increases with its size. Tiny pits of nanometer scale can be seen in the scalding film under a scanning electronic microscope at a higher magnification. The absorptions of the surface plasma scalds tend to be approximately the same as the lower absorptions of test sites without laser irradiation. Scalds do not grow during further illumination pulses until 65 J=cm². The formation of surface plasma scalding may be related to the occurrence of the laser-supported detonation wave.

Single-pulse and multi-pulse damage behaviors of "standard" (with \lambda/4 stack structure) and "modified" (with reduced standing-wave field) HfO2/SiO2 mirror coatings are investigated using a commercial 50-fs, 800-nm Ti:sapphire laser system. Precise morphologies of damaged sites display strikingly different features when the samples are subjected to various number of incident pulses, which are explained reasonably by the standing-wave field distribution within the coatings. Meanwhile, the single-pulse laser-induced damage threshold of the "standard" mirror is improved by about 14% while suppressing the normalized electric field intensity at the outmost interface of the HfO2 and SiO2 layers by 37%. To discuss the damage mechanism, a theoretical model based on photoionization, avalanche ionization, and decays of electrons is adopted to simulate the evolution curves of the conduction-band electron density during pulse duration.

为了研究高功率系统中高反膜的损伤机制, 对高功率系统中最常用的基频高反膜进行了损伤实验。利用台阶仪、扫描电镜、表面轮廓仪等手段, 对实验样品的典型损伤形貌进行了比较和分析。结果表明：保护膜的存在增强了样品的抗激光损伤能力;未加保护膜样品的典型破坏形貌是由材料热物特性差异导致的分层剥落损伤, 这类损伤在后续的脉冲辐照下会迅速发展;有保护膜样品的典型破坏形貌是中心带有μm量级小坑的等离子体烧蚀损伤区, 其主要是由缺陷受热力作用喷溅导致, 小坑附近膜面的凸起是这种力学作用的宏观体现, 这类损伤在后续的脉冲辐照中表现得相对比较稳定。保护膜的存在, 在一定程度上抑制了分层剥落这种灾难性损伤的出现, 改善了样品的损伤特性。

大尺寸磷酸二氢钾(KDP)晶体在惯性约束聚变系统中主要用于制作变频及开关光学元件。在传统生长技术基础上, 开展了点籽晶降温法大尺寸KDP晶体的快速生长技术研究, 设计制作大型培养槽及载晶架, 采用过热注种方式试验点籽晶生长, 培育出尺寸50 cm×50 cm×41 cm的KDP大单晶, 其(100)面生长速度稳定为15 mm/d。晶体在300~1 100 nm波段的透过光谱与常规生长的等同, 影响晶体生长及光学品质的主要的金属杂质离子Fe3+, Cr3+, Al3+等含量少于10-6, 晶体激光损伤基频阈值30 J/cm2, 三倍频阈值达到8.6 J/cm2。

采用传统降温法,利用高纯原料从氘化程度为80%的溶液生长了四方相磷酸二氘钾(DKDP)晶体,并按Ⅱ类三倍频方式切割晶体。三倍频用DKDP晶体的最大问题在于其抗光伤阈值低于KDP晶体,严重限制了激光输出的能量密度和晶体使用寿命。考察了不同波长下三倍频DKDP晶体的损伤阈值,以及激光退火效应。实验表明,激光退火对于DKDP晶体的损伤阈值有显著的提升作用,基频、倍频、三倍频的提升效果分别达到1.4,1.9,2.7倍,是改善DKDP晶体抗光伤能力的有效途径。

An automated damage diagnostic system for collecting plasma flash is developed to diagnose damage in a laser-induced damage threshold (LIDT) test system. Experiment is done to verify the accuracy of this system and analyze the relationship between the plasma signals and the damage morphologies. The results obtained by the system are found to be in excellent agreement with those obtained by the much laborious method of Normaski microscope. Results show that plasma signals above 1 V correspond to the damage morphology of surface discolorations with or without pits in their centers, and plasma signals below or just around 1 V correspond to the damage morphology of pits. The misdiagnosis is attributed to contaminations and air breakdown.

利用电子束蒸发和自动晶控技术制备了氧化铪薄膜,并对薄膜进行了退火处理。通过光致发光(PL)光谱、光致发光激发谱(PLE)和X射线衍射(XRD)等测试对HfO2薄膜进行表征,研究了退火对HfO2薄膜结构及发光特性的影响。室温下对薄膜进行了光致发光光谱测试发现存在4个发射峰,退火后的样品发光强度明显增强。对薄膜的激发谱测试发现激发谱与发射谱之间存在着斯托克斯位移。在退火处理后,X射线衍射表明薄膜的取向性和结晶度都明显提高,但是薄膜的激光损伤阈值(LIDT)没有变化。