Abstract: To analyze the influences of surfaces topography on the laser damage and performance of KH2PO4（KDP） crystal, the frequency features of machined surface KDP crystal surfaces were extracted and reconstructed by power spectral density and continuous wavelet transform. Wave optics theory was used to analyze the influences of frequency features on the subsurface light temperature fields of KDP crystals irradiated by 1.064 μm laser wavelength with the power of 20 MW/μm2 for 1ns. The results show that temperature of KDP crystals becomes larger with wavelength of surface frequencies closer to incident laser wavelength(1.064 μm). If the wavelength is over 20 μm, temperature of KDP crystals is unchanged with the changing of frequency features. The obvious wavelengths on the machined surface of KDP crystals obtained by cutting experiments are as 14 μm, 50 μm and 140 μm respeclively, and the subsurface temperature of KDP crystals affected by these frequency features rises are as 56 K, 22 K and 12 K. Maximum temperature of KDP crystals increases with the increasing of amplitude under the same wavelength. With the increasing of surface frequency wavelength, the position of the maximum temperature extends to the interior of the KDP crystals.

Key words:  , machined surface, wavelength, amplitude, KH2PO4(KDP) crystal, light field, temperature field

摘要： 为了更加准确地分析表面形貌对KH2PO4(KDP)晶体元件激光损伤和使用性能的影响，通过功率谱密度和连续小波变换对KDP晶体已加工表面存在的实际频率特征进行提取和重构。利用波动光学理论分析经入射波长1.064 μm、功率20 MW/μm2的激光束照射1 ns后，表面频率特征对KDP晶体亚表层光场及温度场的影响。结果表明，当表面频率特征的波长越接近入射光波长1.064 μm，KDP晶体亚表层的光场畸变现象越严重，会造成局部聚焦，温度越高；当波长超过20 μm时，在振幅不变的情况下，最高温度随着波长的增加基本不变。通过切削实验获得的KDP晶体已加工表面上明显存在的波长分别为14 μm、50 μm和140 μm，对KDP晶体亚表层造成的温升分别为56 K、22 K和12 K。当波长相同时，KDP晶体的最高温度与表面频率幅值成线性关系。随着表面频率波长的增加，温度最高点的位置向KDP晶体内部延伸。

关键词: 已加工表面, 波长, 振幅, KDP晶体, 光场, 温度场