采用傅里叶模方法, 分析了单点金刚石铣削后KDP晶体表面小尺度波纹的周期和幅值对单层增透膜折射率、厚度以及透射率的影响。研究表明: 膜层最佳折射率在1.22左右, 在此折射率条件下, 保证透射率大于99%的单层增透膜的理想厚度范围应为180~220 nm, 并且折射率和膜厚值的选取基本不受晶体表面小尺度波纹周期和幅值的影响。若只考虑SPDT法加工后KDP晶体表面小尺度波纹周期和幅值的实际范围, 透射率基本不受波纹周期的影响, 但却会随波纹幅值的增大而加速下降。理想镀膜条件下透射率最大值大于99%, 并且通常在99.67%~99.94%之间。

The effects of the period and amplitude of micro-waveness on KDP surface processed by single point diamond turning(SPDT) on the refractive index, thickness, and transmittance of single-layer anti-reflection(AR) coating were analyzed by the Fourier modal method. It is found that the optimal refractive index of the AR film is about 1.22, and the thickness should be 180 to 220 nm in order to ensure the transmittance of more than 99% in the optimal refractive index condition. The period and amplitude of micro-waveness on the surface of KDP crystal do not generally affect the values of the optimal refractive index and the reasonable thickness range of single-layer AR coating. Just considering the practical range of the period and amplitude of micro-waveness, the transmittance is not affected by the period, while it drops quickly as the amplitude increases. The maximum transmittance is more than 99% in the ideal coating condition, and it ranges generally from 99.67% to 99.94%.