Study on UV-laser fatigue damage of sol-gel antireflective coating using XPS and slow positron beam Doppler broadening spectrum

The fatigue damage behavior of antireflective coating over KDP crystal under vacuum environment was studied with varied UV-laser irradiation, and the dynamic process from initial damage to complete failure of this coating was obtained. Scanning electron microscope (SEM) and slow positron beam (SPB) technique was employed to study the macro- and micro-defects in the process of evolution. The formation of non-bridging oxygen (NBO) and the variation of O/Si ratio along the direction of coating depth were obtained during the damage process based on X-ray photoelectron spectroscopy (XPS). The idea that oxygen with low binding energy absorbs UV light and produces oxygen defects to induce damage was put forward, and the damage mechanism of sol-gel antireflective coating under UV-laser irradiation was given.