Beam shaping via polarization and vortex modulation for well-defined grooves in metal thin films laser patterning

Abstract

Achieving high-precision electrical isolation in metal thin films through femtosecond laser ablation remains challenging due to the strong influence of spatial energy distribution. While annular beam profiles with uniform energy deposition have demonstrated advantages in improving processing homogeneity, their generation via polarization modulation remains seldom explored. This study systematically investigated the role of polarization states in shaping beam energy profiles and corresponding ablation outcomes. A comparative study of four representative polarization states—linear, circular, radial, and azimuthal, and circularly polarized vortex laser—was conducted under unified femtosecond laser processing conditions, encompassing both single-pulse and groove ablation with the support of Richards–Wolf vector diffraction modeling. The results showed that radial, azimuthal, and circularly polarized vortex lasers produced flat-bottomed grooves with minimal ridge heights (∼0.2 μm) and negligible substrate damage at high overlap rates, benefiting from their annular energy profiles. In contrast, linear and circular polarizations yielded V-shaped grooves and induced significant substrate damage under similar conditions. This work provided a polarization–process performance map and provided a practical framework for optimizing polarization selection in laser processing of flexible electronics, transparent electrodes, and other functional thin-film devices.