Light-induced matrix softening of Ge-As-Se network glasses.

Sub-band-gap irradiation of a series of bulk Ge-As-Se glass samples with a tunable laser source shows that photostructural processes in chalcogenide glasses are strongly dependent on the covalent network connectivity. The photoexcitation process is affected by the bond density as well as the network rigidity. Photostructural changes such as photodarkening and photoexpansion decrease and tend to vanish in overcoordinated glass in accordance with the rigidity percolation threshold. Also, the intensity required to achieve photofluidity is linearly dependent on the bond density. These results provide quantitative support for a description of photofluidity as a summative bond breaking process.