Dependence of Film Porosity on the Adsorption and Removal of Organic Contaminants from the Surface of Optical Components

Damage caused by organic contaminants on the surface of thin films of optical components limits the loading capacity enhancement of inertial confinement fusion. In this study, the effect of porosity of 30-70% porous silica films on contaminant adsorption and laser removal behavior was analyzed by molecular dynamics modeling. The results show that the film porosity is positively correlated with the contaminant adsorption capacity, but 70% porosity leads to pore inhomogeneity, which affects the adsorption uniformity and efficiency. Appropriate laser energy density can improve the contaminant removal efficiency, but an energy density of 20 J/cm² leads to contaminant accumulation and reduces the removal effect. High-porosity film surfaces have a poorer ability to absorb laser energy, leaving fewer contaminants and lower removal efficiency. In addition, the increased porosity makes the films more susceptible to laser energy, resulting in significant variations in Si-O bond lengths, Si-O-Si bond angles, and radial distribution function values after laser cleaning, leading to structural instability. These results emphasize the critical role of film porosity in maintaining the cleanliness of optical components and provide an important reference for designing efficient thin film structures.