Nano-FTIR spectroscopy reveals SiO2 densification within fs-laser induced nanogratings
Nadezhda Shchedrina, Gergely Nemeth, Ferenc Borondics, Nadege Ollierb and Matthieu Lancry
Nanoscale Advances 6, 5164 (2024)
This study explores the structural transformations induced by femtosecond (fs) laser inscriptions in glass, with a focus on type II modifications (so-called nanogratings), crucial for advanced optical and photonic technologies. Our novel approach employs scattering-type scanning near-field optical microscopy (s-SNOM) and synchrotron radiation nanoscale Fourier-transform infrared spectroscopy (nano-FTIR) to directly assess the nanoscale structural changes in the laser tracks, potentially offering a comprehensive understanding of the underlying densification mechanisms. The results reveal the first direct nanoscale evidence of densification driven by HP-HT within fs-laser inscribed tracks, characterized by a significant shift of the main infrared (IR) vibrational structural band of silica glass. It reveals moreover a complex interplay between type I and type II modifications.