Examination of laser-induced heating on multi-component chalcogenide glass

Next-generation infrared (IR) optical components based on chalcogenide glasses (ChGs) may include structures which benefit from the enhanced optical function offered by spatially modifying regions with a nanocrystalline phase. Such modification may be envisioned if the means by which such spatial control of crystallization can be determined using the advantages offered through three-dimensional direct laser write (DLW) processes. While ChGs are well known to have good transparency in the IR, they typically possess lower thresholds for photo- and thermally- induced property changes as compared to other glasses such as silicates. Such low thresholds can result in material responses that include photoexpansion, large thermo-optic increases, mechanical property changes, photo-induced crystallization, and ablation. The present study examines changes in ChG material response realized by exposing the material to different laser irradiation conditions in order to understand the effects of these conditions on such material property changes. Thresholds for photoexpansion and ablation were studied by varying the exposure time and power with sub-bandgap illumination and evidence of laser induced phase change were examined. Simulations were carried out to estimate the temperature increase from the irradiation and the tolerances and stability of the calculations were examined. The models suggest that the processes may have components that are non-thermal in nature.