Hybrid femtosecond laser and ion-implantation processing for controlled, deep, high-efficiency ablation in fused silica

• A hybrid process for the surface modification of fused silica has been demonstrated, combining prior MeV Au-ion implantation with subsequent femtosecond laser irradiation. • Single-shot irradiation of Au-implanted samples produces, independently of the laser fluence, sharply defined cylindrical craters with flat bottoms with 550 nm depth. • The preferential energy absorption induced by the implanted Au layer enables efficient material removal at moderate peak laser fluence, achieving ablation efficiencies up 15 µm 3 /µJ. • A simple cylindrical-crater model accurately predicts the experimental ablation efficiency, providing a guideline for optimizing laser processing and predicting crater shape and efficiency based on the Au-implantation depth. Femtosecond laser modification of fused silica enables precise surface tailoring for the fabrication of micro-optical components such as microlenses and diffractive elements. However, the process is governed by laser–matter interactions where the local fluence determines the processing depth, often limiting control over feature geometry and efficiency. Here, we present a hybrid approach combining localized Au implantation (1.8 MeV Au 2+ ions) into SiO 2 samples with femtosecond laser irradiation (250 fs), effectively tuning the laser–matter interaction and resulting morphology. At both 515 nm and 1030 nm irradiation wavelengths, single-shot femtosecond pulses produce cylindrical craters with sharp edges and flat-bottom profiles. Independently of the fluence, these craters exhibit a constant depth of 550 nm, corresponding to the region of maximum Au concentration. The effect manifests already at moderate fluence (∼4 J/cm 2 ) and yields high ablation efficiency, up to 15 µm 3 /µJ. The hybrid method also works effectively at lower implantation doses that preserve the excellent transmission of fused silica, offering a promising pathway for the high-quality fabrication of flat optical components such as binary phase masks, phase lenses, or fused-silica micromolds.