Maximal Photodarkening in the Ge–As–S Glass System

Abstract

Many studies have been conducted on the photodarkening in chalcogenide glasses, and a maximal change is demonstrated to appear around Ge20As25S55. However, the reason for this selected composition remains unanswered, for which a plausible idea is proposed here. It seems that the composition has a maximal atomic volume in the ternary system, which probably gives rise to least photoexpansion (or photocontraction). The idea suggests that disordered, moderately‐rigid networks are effective in enhancing the photodarkening through suppressing macroscopic viscous relaxation.