Journal Of Non Crystalline Solids vol:230 Part B pages:694-699
Metastable photoinduced anisotropy (PA) generated by linearly polarized sub-bandgap light is reported for undoped and Pr-doped Ge-S-I, Ge-Ga-S and As-Ga-S glasses with varying composition and Pr content. Compositional trends of PA are related to the light-stimulated reorientation of intrinsic anisotropic centers and their environments, which vary with composition. These centers can be modeled with pairs of over- and under-coordinated sulfur atoms: the valence alternation pairs (VAPs). The addition of Pr up to a level of about 1000 ppm affects PA, suggesting that this concentration is comparable with the concentration of VAPs. Microscopic models are proposed for the centers responsible for PA in these glasses. (C) 1998 Elsevier Science B.V. All rights reserved.