摘要： The boson band mapping of waveguides fabricated by femtosecond laser inscription was used for the first time to identify and understand the material densification profile in chalcogenide glasses. The refractive index mapping of waveguides in high refractive index dielectrics is problematic as there are no known techniques. Refracted near field technique cannot be carried out in glasses with refractive index higher than 1.6 due to the lack of availability or toxic nature of the index matching oil. Though other techniques based on holographic and phase microscopies are available, sample preparation steps compatible with reliable measurement are tedious and in some cases, like diamond, is almost impossible. In this work, using the information obtained from the Bosonic band vibrations, we explain waveguide formation in Gallium Lanthanum Sulphide (GLS) glass. The boson peak shows up in any amorphous material regardless of its constituents or stoichiometry and is observed in the low frequency region between 0 – 100 cm-1. Their origin is a well debated and controversial topic. Here we make use of its response to the physical properties of the material.