Drill-bit-inspired dynamic focal fields for augmented laser materials processing

Abstract

Laser manufacturing has advanced through increasingly precise control of power, pulse duration, repetition rate and scan trajectory, yet the spatial intensity profile of the beam is still usually fixed during light-matter interaction. This constraint limits how energy can be delivered to matter, particularly in processes where melt flow, material removal and surface morphology evolve on comparable time and length scales. Here we introduce drill-bit-inspired laser beams that convert the focal intensity distribution from a passive, static spot into an active, programmable processing tool. By combining cylindrical vector beams with rotational vectorial polarization filtering, we create a near diffraction limited two lobe Hermite-Gaussian focus that continuously spins about the propagation axis and can be reconfigured on demand. We establish two operating regimes, dynamic beam spinning and instantaneous beam-profile shifting, and derive closed-form descriptions of the accumulated fluence and effective pulse number governed by the along-scan pitch l = u/f, where u is the scan speed and f is the spin frequency. Across continuous-wave and ultrashort-pulse regimes, this dynamic energy deposition enables low-power metal machining with drilling efficiencies about four times higher than static Gaussian, enhances convective melt flow, promotes pore resorption and reduces retained porosity in keyhole welding, as visualized by in situ X-ray imaging, and turns simple linear scans into programmable surface textures. These results show that dynamic focal-profile control can extend laser processing beyond static beam shaping, opening a broadly applicable route to programmable energy deposition in manufacturing.