Reversible and irreversible photon-absorption in amorphous SiO2 revealed by deep potential

Abstract

Understanding the kinetic balance between reversible and irreversible photon-absorption (IPA/RPA) in amorphous-SiO2 (a-SiO2) is crucial for mitigating optical damage and assessing the lifetime of irradiated optics. Experimental work has placed some thermodynamic bounds on the formation of defects from damage precursor, but the formation kinetics and underlying microscopic mechanisms are yet to be elucidated. Here, by employing deep neural network potential, we find that the formation of defects are temperature-dependent and density-dependent, where competitions between IPA and RPA take place. The IPA prevails in the early formation of E’-center, and the ratio of IPA/RPA is related to the strained bonds, SiSi bonds and 5-coordinated silicon (Si5). Furthermore, the Si5 is critical to the propagation of E’-center and densification of a-SiO2. Additionally, we develop quantitative models of defects in regard with irradiation temperature of specified temperature and irradiation photon-energy, respectively.