Repulsive magnetic field-enhanced laser-induced plasma-assisted ablation for high-efficiency and high-quality sapphire microfabrication

Nanosecond laser microfabrication of sapphire remains challenging due to its broadband optical transparency and pronounced thermal effects. In this paper, a repulsive magnetic field-enhanced laser-induced plasma ablation (LIPAA) technique is proposed to improve processing efficiency and fabrication accuracy. The processing quality of sapphire microstructures is investigated at different magnetic induction intensities. The repulsive magnetic field effectively suppresses the horizontal expansion of plasma plume, forming deeper and narrower ablation craters. At the optimal magnetic induction intensity of 400 mT, the sapphire microfabrication achieves a 4.6-fold increase in materials’ removal rate and a 72% reduction in sidewall roughness compared to the LIPAA without magnetic field assistance. This improvement is attributed to the reduction of Larmor radius under the magnetic confinement, which concentrates the plasma into a smaller ablation area. A uniform microcolumn array is successfully fabricated on sapphire, demonstrating its potentials in optical device microstructures.