Effect of Ga and Se addition on the “near-surface” photo-response of new Ge-based chalcogenide glasses under IR femtosecond laser exposure

Abstract In this paper, we report results of a systematic study to evaluate the relationship between compositional variation and the photo-response of Gallium containing sulfo-selenide glasses upon IR femtosecond laser exposure. We show that IR femtosecond laser irradiation in this system results in near-surface photo-expansion, which based on micro-Raman spectroscopy, has been related to an increased connection of GeS 4 units to form corner sharing GeS 4/2 units with a concurrent formation of S–S bridges. The lower surface photo-expansion of the Ga- containing sulfide and sulfo-selenide glasses compared to that of the Ga-free sulfide and sulfo-selenide glasses has been related to the presence of GaS 4 and Se–Se isolated units in the germanate glass network which are expected to restrict the connection between GeS 4 units during laser exposure. Such mechanistic understanding of material modification opens the pathway towards the laser writing of active photonic devices in the near-surface of these glasses.