High-power laser-induced spectrum analyzer was applied to reveal transient material variations in KDP/DKDP crystals. A long-wave pass large-angle filter structure was used to efficiently filter the high-power laser-induced Rayleigh scattering. The Raman spectra excited by a high-power nanosecond laser were compared with that by a low-power continuous-wave (CW) laser. Significant increase of Raman spectra related to the molecular vibration of hydroxyl and hydrogen bonds (1000–3000 cm⁻¹) under high-power laser were obviously detected. The emission spectra in the damaged and undamaged sites were compared. It was found that the intensity of the Raman scattering decreased, and an emission peak at 467 nm was detected after the damage. Moreover, stronger intensity of the stimulated Raman scattering corresponds to higher laser damage threshold. Based on these results, the generation of transient defects was discussed. The irradiation of the high-power laser provided sufficient energy for the intense vibration of hydroxyl and hydrogen bonds, thus breaking bonds and generating transient defects. Furthermore, the energy level of the defects corresponded to the emission peak centered at 467 nm, thereby becoming the precursor of laser damage.

使用大功率激光感应光谱分析仪来揭示KDP / DKDP晶体中的瞬态材料变化。长波通大角度滤光片结构用于有效滤除高功率激光诱导的瑞利散射。将高功率纳秒激光器激发的拉曼光谱与低功率连续波（CW）激光器的拉曼光谱进行比较。与羟基和氢键（1000–3000 cm ^-1的分子振动）有关的拉曼光谱显着增加）在高功率激光下被明显检测到。比较了受损和未受损部位的发射光谱。发现拉曼散射的强度降低，并且在损伤后检测到在467nm的发射峰。而且，受激拉曼散射的强度越强，对应的激光损伤阈值越高。基于这些结果，讨论了瞬态缺陷的产生。高功率激光的照射为羟基和氢键的剧烈振动提供了足够的能量，从而破坏了键并产生了瞬态缺陷。此外，缺陷的能级对应于以467nm为中心的发射峰，从而成为激光损伤的先兆。