Femtosecond laser-induced periodic surface structure on fused silica surface

Single and 10-pulse laser-induced surface damage behaviors of fused silica were investigated using a linearly polarized 40-fs Ti: sapphire laser system operating at a central wavelength of 800 nm. After the sample was subjected to single-shot laser irradiation, it displayed a typically damaged crater, and two types of laser-induced periodic surface structures (LIPSS) on the surface of the damage crater were found under 10-pulse laser irradiation. By increasing the laser fluence, the LIPSS orientation rotated by 90°, and the period changed from 300 nm to 700 nm. Under near-threshold laser irradiation, an intermittent LIPSS, whose orientation was perpendicular to the laser beam polarization direction and average spatial period was around 300 nm, was found on the damaged area. Another type of LIPSS, which was parallel to the laser beam polarization and had a period of approximately 700 nm, was continuously formed at the bottom of the ablation crater when the laser fluence exceeded the damage threshold of material. A model based on the theory of interference between the incident laser and the surface scattered wave was adopted to explain the formation mechanism of the LIPSS.