Spectral domain analysis of surface roughness evolution during femtosecond laser deep engraving of glass

Control of surface roughness during ultrashort laser processing remains challenging due to an incomplete understanding of the mechanisms governing its evolution, despite its critical role in determining surface properties. In this study, we analyze the evolution of the surface texture of laser-processed fused silica samples by performing spectral analysis. Spectral analysis reveals that surface roughness evolution is influenced by scanning strategy and its parameters, the presence of laser-induced nanoripples, and newly generated low spatial frequency features. Furthermore, we observe that texture evolves differently depending on the initial surface roughness due to varying attenuation rates of different spatial frequencies.