In-Situ and Ex-Situ Characterization of Femtosecond Laser-Induced Ablation on As2S3 Chalcogenide Glasses and Advanced Grating Structures Fabrication

Femtosecond laser pulse of 800 nm wavelength and 150 fs temporal width ablation of As2S3 chalcogenide glasses is investigated by pump-probing technology. At lower laser fluence (8.26 mJ/cm(2)), the surface temperature dropping to the melting point is fast (about 43 ps), which results in a clean hole on the surface. As the laser fluence increases, it takes a longer time for lattice temperature to cool to the melting point at high fluence (about 200 ps for 18.58 mJ/cm(2), about 400 ps for 30.98 mJ/cm(2)). The longer time of the surface heating temperature induces the melting pool in the center, and accelerates material diffusing and gathering surrounding the crater, resulting in the peripheral rim structure and droplet-like structure around the rim. In addition, the fabricated long periodic As2S3 glasses diffraction gratings can preserve with high diffraction efficiency by laser direct writing technology.