Spatially resolved correlation between glass structure and refractive index modifications resulting from irradiation of chalcogenide glass by femtosecond pulse train

A detailed analysis of 2D μ-Raman mapping of refractive index variation (Δn) induced by femtosecond filament in the bulk of a ternary (Ge-Ga-S) chalcogenide glass is presented. The results demonstrate strong structural modifications. S3Ga-GaS3 ethane like units are transformed into triclusters of Ga/S. Also the decrease of the population of GeS4/2 tetrahedrons implies the formation of mixed triclusters T/S where T=Ga and/or Ge. Finally, the refractive index variation is correlated to the structural modifications