Model for photoinduced anisotropy and its dark relaxation in chalcogenide glasses

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Abstract
The relaxation kinetics of photoinduced anisotropy (PA) in chalcogenide glasses in the dark, subjected to repeated switching on and off of the linearly polarized inducing light, can be approximated by a simple exponential in the initial stages only and by a stretched exponential (Kohlrausch law) at later stages. The parameters of these decays are changed only weakly for simple exponential decay, but strongly for stretched exponential decay, after repeated switching on and off of the inducing light. A model is put forward to account for the PA effect, as well as the changes in its dark-relaxation kinetics, based on structural changes of intimate valence-alternation pairs and their environments, resulting in changes of their microanisotropy and chirality in accordance with the polarization of the inducing light.