KDP类晶体是唯一可以满足ICF激光驱动装置通光口径的非线性光学晶体材料。该类晶体采用水溶液生长法生长，易于产生宏观包裹体和微观晶格缺陷，在高功率激光辐照下晶体内部易产生高密度pinpoint损伤现象，这与其他方法生长的晶体只是受限于光学加工的表面损伤问题相比具有明显不同。KDP类晶体内部的缺陷或前驱体诱导激光损伤与晶体切向、激光波长及偏振方向等密切相关，使得应用于ICF激光驱动器中不同光学功能的、来源于同一晶坯的不同晶体元件也表现出损伤性能的差异性，因此其损伤机理非常复杂，迫切需要认识该类晶体的激光损伤机理问题。回顾了上海光学精密机械研究所联合福建物质结构研究所、山东大学等晶体研制单位联合开展的关于KDP类晶体激光诱导损伤特性的研究工作，进行了用于光开关、倍频以及混频等功能的KDP和不同氘含量DKDP晶体的激光损伤研究，指导了晶体生长工艺优化和过程关键因素控制，并对仍存在的问题及解决方案进行了展望，对于高性能KDP类晶体的研制以及在高功率激光系统中的合理应用具有参考价值。

Indium tin oxide (ITO) films have recently emerged as a new class of functional materials for nonlinear optical (NLO) devices due to their exotic properties around epsilon-near-zero (ENZ) wavelength. Here, we experimentally investigated and tailored the NLO absorption properties of ITO films. The NLO absorption response of ITO films is investigated by using the femtosecond Z-scan measurement technique at two different wavelengths of 1030 nm (out of ENZ region) and 1440 nm (within ENZ region). Interestingly, we observed conversion behavior from saturable absorption (SA) to reverse saturable absorption (RSA) at 1030 nm with the increasing incident laser intensity, whereas only SA behavior was observed at 1440 nm. We demonstrate that SA behavior was ascribed to ground-state free electrons bleaching in the conduction band, and RSA was attributed to three-photon absorption. Moreover, results reveal that ITO film shows more excellent SA performance at 1440 nm with a nonlinear absorption coefficient of ～-23.2cm/GW and a figure of merit of ～1.22×10-16esu·cm. Furthermore, we tailored the SA and RSA behaviors of ITO films at 1030 and 1440 nm wavelengths via post-annealing treatment. The modulatable NLO absorption was ascribed to the changing of free-carrier concentration in ITO films via annealing treatment. The experimental findings offered an inroad for researchers to tailor its NLO absorption properties by changing the free-carrier concentration through chemical modification such as annealing, oxidation, or defect implantation. The superior and tunable nonlinear optical response suggests that ITO film might be employed as a new class material with potential applications in novel optical switches or optical limiters to realize the all-optical information process.

Ultrathin Ge films with thickness of about 15 nm at different deposition temperatures were prepared by electron beam evaporation. Spectral measurement results showed that as the deposition temperature increased from 100°C to 300°C, the transmittance of the films in the wavelength range from 350 nm to 2100 nm decreased. After annealing in air at 500°C, the transmittance significantly increased and approached that of uncoated fused quartz. Based on the Tauc plot method and Mott–Davis–Paracrystalline model, the optical band gap of Ge films was calculated and interpreted. The difference in optical band gap reveals that the deposition temperature has an effect on the optical band gap before annealing, while having little effect on the optical band gap after annealing. Furthermore, due to oxidation of Ge films, the optical band gap was significantly increased to ～5.7 eV after annealing.

A time-resolved high-power laser photometer, which measures the real-time variations of transmission, internal reflection, and scattering simultaneously with picosecond time resolution, was developed to investigate the material response sequence during high-power nanosecond laser irradiation in thick fused silica. It was found that the transient transmission decreased sharply, accompanied by an increase in internal reflection at the rising edge of the laser pulse. The transient transmission recovered, while laser damage did not occur, but it did not recover if the scattering increased, indicating the occurrence of laser damage. The reason for the sharp decrease of transmission and the relationship between the transmission drop and laser damage were discussed.

The spatial resolved method, which measures the laser-induced damage fluence by identifying the location of the damage point in the Gaussian beam three-dimensional direction, is demonstrated. The advantages and practicality of this method have been explained. Taking a triple frequency beam splitter as an example, the defect damage fluence can be accurately calculated by the spatial resolved method. The different defect damage performance of the triple frequency splitter is distinguished under irradiations of only the 355 and 532 nm lasers. The spatial resolved method provides a way to obtain precise information of optical film defect information.

Laser-induced modification at 355 nm of deuterated potassium dihydrogen phosphate (DKDP) crystals following exposure to nanosecond (ns) and sub-ns laser irradiation is investigated in order to probe the absorption mechanism in damage initiation. Laser damage resistance is greatly improved by sub-ns laser conditioning, whereas only a little improvement occurred after ns laser conditioning at the same laser fluence. Moreover, scattering and transmittance variations after the two types of laser conditioning indicate similar reduction of linear absorption. However, by contrast, large differences on nonlinear absorption modification are discovered using Z-scan measurement. This characteristic absorption modification by laser irradiation provides evidence that a nonlinear absorption mechanism plays a key role in damage initiation at 355 nm.

The nonlinear absorption (NLA) properties of potassium dideuterium phosphate crystals at 515 nm under different excitation laser intensities are investigated with the Z-scan technique. Two critical intensities are highlighted: the critical intensity for exciting the NLA and the critical intensity of the multiphoton absorption mechanism transition. Experimental results indicate the existence of defect states located in the band gap, which can be manipulated by varying laser intensity. A model based on the change of multiphoton absorption mechanism induced by the transformation of defect species is proposed to interpret the experiments. Modeling results are in good agreement with the experiment data.