Photodarkening in Ge3Se17 glass

In this paper, we present measurements of the kinetics of photodarkening in Ge3Se17 glass. The photodarkening is induced with sub-bandgap light and observed as transmission changes through a 1 mm thick sample of the glass. Both transient nonlinear and permanent processes are detected with these measurements. We consider the various sources that could lead to changes in sample optical properties and suggest that changes in electronic structure are the most reasonable explanation for the observed photodarkening. Comparison of the results with a model of light induced changes in amorphous selenium leads to an explanation for these effects based on the formation of dynamical bonds during illumination.