Laser nanoprocessing via an enhanced longitudinal electric field of a radially polarized beam

Single-shot laser ablation is performed on the surface of a transparent glass material using a radially polarized femtosecond beam. Theoretical and experimental investigation revealed the significant role of the material interface under high-numerical-aperture conditions. The longitudinal electric field at the focus was remarkably enhanced due to the total reflection on the interface when a radially polarized beam was focused on the back surface of the glass from the inside using an immersion lens. This focusing condition enabled the fabrication of a small ablation hole sized 67 nm. This study offers a novel, to the best of our knowledge, approach to realize laser nanoprocessing with radially polarized beams.