Influence of surface roughness on interfacial adsorption and laser ablation mechanisms of organic contaminants on fused silica

Abstract

The deleterious effects of organic contaminants on optical components are a major obstacle to high-energy laser systems, and laser ablation is an important means of removing contaminants. Nevertheless, irregularities or flaws created during the manufacturing process of optical element surfaces affect the absorption of organic contaminants while placing higher demands on laser ablation. Hence, it is imperative to comprehend the intricate interplay among surface roughness, contaminant absorption, and ablation in order to effectively confront the challenge of laser-induced damage. In this study, the three-dimensional morphology of the fused silica surface was simulated numerically employing the Weierstrass-Mandelbrot fractal function. On this basis, we developed a theoretical model through molecular dynamics simulations to gain insight into the adsorption process of dodecane organic molecules on fused silica surfaces. Building upon the obtained outcomes, the effect of surface roughness on the laser removal of the adsorbed model is comprehensively analyzed. The findings reveal that dodecane molecules tend to aggregate within enclosed crevices and irregular regions, resulting in heightened localized density. Additionally, an augmented substrate surface roughness diminishes van der Waals energy and pressure, thereby facilitating the elimination of contaminants. These findings are indispensable for deepening our understanding of the dynamic interactions involving lasers, fused silica, and organic contaminants, as well as providing valuable insights into effectively addressing the challenging issue of laser-induced damage.