The organic contamination damage of large-aperture optical components limits laser energy improvement of inertial confinement fusion (ICF). In situ cleaning of large-aperture optical components via low-pressure plasma is expected to remove organic contaminants from the optical surface. Herein, low-pressure air plasma equipment was proposed and used on surfaces of SiO2 sol–gel antireflection (AR) films in situ by conducting experiments. Its electrical discharge parameters were investigated and optimized during plasma cleaning. Plasma diffusion characteristics and homogeneity in large-aperture windows were analyzed by optical emission spectroscopy. Dramatic degradation in the optical properties of components was observed after organic contamination for 5 h. Transmittance, laser-induced damage threshold and surface morphology observation results demonstrated that low-pressure air plasma removed the organic contaminants from the surface of sol–gel AR films without causing damage and metal contamination. After plasma cleaning, the hydrophilicity of the films increased significantly due to the increase in the polar components of surface free energy. The mechanism of plasma cleaning organic contaminants was confirmed by x-ray photoelectron spectroscopy measurements. These salient results provide a new alternative method for removing organic contaminants in situ from large-aperture optical components and a foundation for improving the energy output of the ICF system.
大口径光学元件的有机污染限制了惯性约束聚变（ICF）激光能量的提升。通过低压等离子体对大口径光学元件进行原位清洗，有望去除光学表面的有机污染物。本文提出了一种低压空气等离子体设备，并对其在SiO₂溶胶-凝胶（sol–gel）增透膜表面进行了原位清洗实验。研究了清洗过程中的放电参数并进行了优化。利用发射光谱分析了大口径窗口中等离子体的扩散特性和均匀性。实验观察到，有机污染5小时后，元件的光学性能显著下降。透射率、激光损伤阈值及表面形貌观察结果表明，低压空气等离子体能够去除溶胶-凝胶增透膜表面的有机污染物，且不造成损伤或金属污染。清洗后，薄膜的亲水性显著提高，这是由于表面自由能中极性分量增加所致。X射线光电子能谱分析证实了等离子体清洗有机污染物的机理。这些重要结果为大口径光学元件有机污染物的原位去除提供了一种新方法，并为提升ICF系统的能量输出奠定了基础。