高精度KDP晶体是惯性约束核聚变光路系统中的重要元件,而已加工表面的小尺度波纹对光学元件的透射比有着重要影响。采用傅里叶模方法理论分析了表面小尺度波纹的幅值及周期对KDP光学元件透射比的影响。研究结果表明,当小尺度波纹幅值小于100 nm时,透射比随波纹幅值的增加基本呈线性增长,波纹幅值每提高10 nm,透射比可提高近0.5%;透射比随着小尺度波纹周期的增加围绕中心透射比上下浮动,透射比振幅基本保持不变,且中心透射比及透射比振幅均随着小尺度波纹幅值的增加而增大;小尺度波纹周期在10.5-12 μm区间内时透射比明显很低,需采取措施避免小尺度波纹的周期出现在此区间。对KDP晶体进行了加工、表面形貌检测及透射比检测的实验,实验结果与理论计算结果基本吻合。

High-precision KDP optical element is a key component in ICF optical system. The micro-waveness on the machined KDP surface has a significant impact on its transmittance. The effect of micro-waveness amplitude and period on the transmittance of KDP optical element is discussed by Fourier modal theory. Results indicate that:the transmittance increases linearly as the micro-waveness amplitude grows (about 0.5% per 10 nm) when the micro-waveness amplitude is less than 100 nm;the transmittance varies around the central value while the transmittance amplitude remains unchanged,and both of them increase as the micro-waveness amplitude grows. The transmittance is very low when micro-waveness period is between 10.5 μm and 12 μm,and measures should be taken to avoid micro-waveness period in such range. Processing,detection experiments of morphological surface and transmittance of KDP crystal are carried out,and the experimental results are consistent with the theoretical calculations basically.