In-situ cleaning organic contaminants on SiO2 sol-gel antireflection film by low-pressure air plasma

Abstract

Organic contaminants on optical components can degrade optical properties, thus limiting the energy enhancement of highpeak- power laser systems. It is still challenging to remove organic contaminants on the SiO2 sol-gel antireflection film and avoid damage. In this work, a low-pressure air plasma in-situ cleaning technique and a chemical reaction model of plasma cleaning were proposed to study the removal of organic contaminants. The optical properties of sol-gel AR films suffered from organic contaminants were evaluated by transmittance and laser-induced damage threshold, which recovered completely after 5 minutes of plasma cleaning without damage. Meanwhile, the hydrophilicity of the surface and the surface free energy were significantly increased after plasma treating. Surface composition analysis indicated that the CH and C-C bonds were reduced considerably, while abundant C=C and C=O bonds were produced after plasma cleaning. Optical emission spectrum analyzed the reactive species and its concentration in the air plasma as a reference for simulation. The chemical interaction process of oxygen radicals with organic contaminants was simulated by reactive molecular dynamics. The results can provide a guide for optical components in-situ cleaning.