Study on Coating Exfoliation Damage Of Kdp Component Under Laser Irradiation By Surface Analysis

Abstract

Potassium dihydrogen phosphate (KDP) is a kind of key component for laser frequency conversion. In this paper, the damage phenomenon of KDP coating caused by multiple laser irradiation under low flux and low vacuum is studied. Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) with C60n+ cluster sputtering in combination with SEM and AFM was employed to provide detailed information on three-dimensional chemical composition and damage deterioration process of this coating. By analyzing the process of coating thinning after irradiation, the detailed chemical changes in the process of coating densification caused by UV laser irradiation were explained. By analyzing the process of coating irradiation damage, the conversion from Si-O-Si bond to Si-O-K bond was found, which supported the phenomenon of coating hardening after damage. Furthermore, dynamic evolution law of coating deformation after laser irradiation was obtained based on the comparison with non-irradiated one. The information including interface bonding between KDP and coating, stratified chemical information of coating along perpendicular direction, and relationship between damage and environment condition is investigated. Based on the previous characterization and analysis, possible mechanism of coating exfoliation after laser irradiation is proposed, providing reference to optimize the laser coating over KDP substrate for laser facility.

Keywords: Laser antireflective coating, exfoliation damage, ToF-SIMS, damage mechanism