采用HPM溶液(盐酸、双氧水和去离子水的混合液)结合氧等离子体对多层介质膜脉宽压缩光栅进行清洗研究。用X射线光电子能谱检测光栅表面的元素成分及其原子含量的变化。实验结果表明, 氧等离子体处理能有效去除光栅表面残留光刻胶和碳氟化合物；再经HPM溶液清洗, 反应离子束刻蚀和氧等离子体处理过程产生的金属污染物被进一步去除。经过上述清洗工艺处理后, 光栅一级衍射效率仍保持在95%以上, 光栅表面激光诱导损伤阈值达到1.6 J/cm2 (1053 nm, 10 ps)。实验结果说明了氧等离子体和HPM溶液相结合能有效清洗多层介质膜脉宽压缩光栅, 并显著提高光栅损伤阈值。

Oxygen plasma and HPM solution (mixtures of hydrochloric acid, hydrogen peroxide, and deionized water) were applied to cleaning the multilayer dielectric (MLD) pulse compressor gratings. X-ray photoelectron spectroscopy was carried out to evaluate surface cleanliness of the gratings. It is found that photoresist and fluorocarbon residues can be efficiently removed with oxygen-plasma cleaning and metal contaminants can be completely removed with HPM cleaning. After cleaning processes, the typical diffraction efficiencies in -1st reflected order are maintained larger than 95.0% at an incidence of 66.4° in TE polarization, and the laser induced damage threshold (LIDT) for 10-ps laser pulse at 1053 nm is greatly improved to 16 J/cm2. The cleaning method using oxygen plasma and HPM solution can efficiently make the surface clean and therefore enhance the LIDT of MLD gratings.