中文摘要：

采用SPDT方法加工获得的KDP晶体表面所残留的小尺度波纹对其激光损伤阈值有着重要影响。利用时域有限差分方法（FDTD）研究了KDP晶体已加工表面存在的小尺度波纹对晶体内部近场光强分布的影响。通过对数值模拟结果的分析发现：表面残留的小尺度波纹,会使晶体内部的衍射场发生畸变,导致晶体内部光强沿横向和纵向呈现周期性的强弱分布;当小尺度波纹周期小于0.7μm时,其对晶体内部光强的调制作用很小,此时光强以倏逝波的形式在波纹附近产生调制;1.064μm时相对光强达到最大值;3μm后基本保持不变,相对光强随着小尺度波纹幅值的增加基本成线性增长,不同周期时增长幅度不同。

英文摘要：

Using single point diamond turning method to process KDP crystals,the micro-waviness,which has a significant impact on the laser induced damage threshold,will be left on the machined surface.The effect of micro-waviness on near-field light intensity distribution was analyzed by Finite Difference Time Domain（FDTD） method.Results indicate that：the micro-waviness will distort the incident wave and lead to periodic distribution of strength and weakness of light intensity along x-and z-axis inside the KDP crystal.When the micro-waviness period is below 0.7 μm,it has a low influence on the modulation of light intensity inside the crystal.Meanwhile,the light intensity modulates around the micro-waviness in the form of evanescent wave.Relative light intensity reaches the maximum in the period of 1.064 μm,and remains unchanged above the period of 3 μm.In the common range of the micro-waviness amplitude,the relative light intensity increases linearly as the micro-waviness amplitude increases,with different slope in different micro-waviness period.