Investigation of the Multimechanism Laser Cleaning Dynamics for Rough Fused Silica Surfaces with Organic...

The detrimental impact of organic contaminants on optical components poses a significant obstacle to high-energy laser systems. However, irregularities or defects on the surface of optical components during manufacturing can affect the process of organic contaminant removal. Thus, a comprehensive understanding of the intricate interplay among surface roughness, contaminant absorption, and ablation is essential to effectively address the challenges of laser-induced damage. In this study, a molecular dynamics approach was employed to investigate the interaction between laser-fused silica and contaminants and to analyze the influence of surface roughness on the removal of contaminants from fused silica. Research findings demonstrate that during laser irradiation, organic contaminants on the surface of mechanical components diffuse into the optical elements. As the laser flux increases, the contaminants gradually decompose into smaller molecular clusters. Additionally, the phenomenon of contaminant ablation is observed to consist of two distinct phases: the "Thermal expansion phase" and the "Thermal ablation phase." The study examines the impact of substrate roughness on the contaminant removal in these two phases. It is found that a higher surface roughness leads to stronger thermal expansion and vaporization of contaminants. With increasing roughness of the fused silica substrate, the corresponding van der Waals energy and pressure decrease under the same laser fluence, making the removal of contaminants easier. These results provide valuable insights into the interaction between laser irradiation and organic contaminants.