To determine whether a potassium dihydrogen phosphate (KDP) surface mitigated by micro-milling would potentially threaten downstream optics, we calculated the light-field modulation based on angular spectrum diffraction theory, and performed a laser damage test on downstream fused silica. The results showed that the downstream light intensification caused by a Gaussian mitigation pit of 800 μm width and 10 μm depth reached a peak value near the KDP rear surface, decreased sharply afterward, and eventually kept stable with the increase in downstream distance. The solved peak value of light intensification exceeded 6 in a range 8–19 mm downstream from the KDP rear surface, which is the most dangerous for downstream optics. Laser damage sites were then induced on the fused silica surface in subsequent laser damage tests. When the distance downstream was greater than 44 mm with a downstream light intensification of less than 3, there were no potential damage threats to downstream optics. The study proves that a mitigated KDP surface can cause laser damage to downstream optical components, to which attention should be paid in an actual application. Through this work, we find that the current manufacturing process and the mitigation index still need to be improved. The research methods and calculation models are also of great reference significance for related studies like optics mitigation and laser damage.

中文翻译：

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后 KDP 表面上的高斯缓解坑对下游光学器件造成的潜在损坏威胁

为了确定通过微铣削减轻的磷酸二氢钾 (KDP) 表面是否会潜在地威胁下游光学器件，我们基于角光谱衍射理论计算了光场调制，并对下游熔融石英进行了激光损伤测试。结果表明，宽度为800 μm、深度为10 μm的高斯缓和坑引起的下游光强在KDP后表面附近达到峰值，之后急剧下降，随着下游距离的增加最终保持稳定。在 KDP 后表面下游 8-19 mm 范围内，求解的光强峰值超过了 6，这对下游光学来说是最危险的。然后在随后的激光损伤测试中在熔融石英表面上诱导激光损伤部位。当下游距离大于 44 毫米且下游光增强小于 3 时，下游光学器件没有潜在的损坏威胁。研究证明，缓和的KDP表面会对下游光学元件造成激光损伤，在实际应用中应注意这一点。通过这项工作，我们发现目前的制造工艺和缓解指标仍有待改进。该研究方法和计算模型对光学缓解、激光损伤等相关研究也具有重要的参考意义。实际应用中需要注意的地方。通过这项工作，我们发现目前的制造工艺和缓解指标仍有待改进。该研究方法和计算模型对光学缓解、激光损伤等相关研究也具有重要的参考意义。实际应用中需要注意的地方。通过这项工作，我们发现目前的制造工艺和缓解指标仍有待改进。该研究方法和计算模型对光学缓解、激光损伤等相关研究也具有重要的参考意义。