使用有限元方法分析了在激光辐照条件下,KDP晶体已加工表面存在的残余内应力、微裂纹及微孔等多种微纳米加工表层缺陷对晶体激光损伤阈值的影响。通过分析发现:KDP晶体微纳米加工表层缺陷的存在,会影响晶体表面的温度场及热应力场的分布,使入射激光的能量积聚在缺陷附近的很小范围内,造成晶体缺陷处产生局部熔融现象,从而使KDP晶体产生损伤,降低KDP晶体的激光损伤阈值。针对微纳米表层的微裂纹进行了损伤阈值测试实验,结果表明微裂纹的存在会降低KDP晶体的激光损伤阈值(约降低3 J/cm2),实验结果与仿真结果符合得很好。

Influences of various micro/nano processing induced surface defects of KDP crystals on laser damage threshold are analyzed by finite element method,which include residual internal stress,micro-crack and micro-pore. It is found that the defects in machined KDP crystal surfaces may affect the distribution of temperature field and thermal stress field of the machined crystal surfaces,which makes the injected laser beams centralize on a small area around the defects,thus leading to partial melting of KDP crystal and laser damage threshold reduction. The laser damage threshold test experiment of the micro-crack is done,and the experiment result shows that the micro-crack will reduce the laser damage threshold of KDP crystal (reducing about 3 J/cm2) and the result fits the simulation result well.