Long-lasting antifogging mechanism for large-aperture optical surface in low-pressure air plasma in-situ treated

Abstract

In this article, the long-lasting antifogging capability of large-aperture optical components was obtained by the in-situ plasma treatment. Water contact angle and surface free energy were used to study the overall antifogging evolution of optical components in the air. The optical performance, including laser-induced damage threshold and surface morphology, were discussed after plasma cleaning. Elements contents and functional groups information were analyzed by X-ray photoelectron spectroscopy detection as a reference to simulation results. In molecule dynamics simulations, the substrates of fused quartz were modified by linking various functional groups (-H, –OH, –CHO, –COOH, –NH2) to simulate the surface of optical components after plasma treatment at a microscopic level. Experimental results showed that the surface of the optical components (fused quartz, sol-gel antireflection film, multilayer dielectric film) treated by plasma had a good antifogging effect, which can be maintained for 300 min. The surface wettability of optical components was improved significantly after plasma treatment, which was supported mainly by the polar components in the surface free energy. Besides, The optical performance of the components was enhanced while the surface structure was barely damaged. According to simulation results, it was found that –CHO, –COOH, and –NH2 played a dominant role in improving the hydrophilicity of optical components, compared with -H, –OH. The hydrophilic surfaces after plasma modification were obtained because more hydrogen bonds were generated between the surface functional groups and the water molecules. The above research provides a new method and a theoretical basis for improving the long-lasting antifogging for large-aperture optical components.