High-power Yb-based all-fiber laser delivering 300 fs pulses for high-speed ablation-cooled material removal

We report on a 72 W Yb all-fiber ultrafast laser system with 1.6 GHz intra-burst and 200 kHz burst repetition rate developed to demonstrate ablation-cooled material removal at high speeds. Up to 24 W is applied on Cu and Si samples with pulses of similar to 300 fs, and record-high ablation efficiencies are obtained, compared to published results to date, despite using only similar to 100 nJ pulses. Ablation speeds approaching 1 mm(3)/s are reported with 24 W of average power, limited by available laser power and beam scanning speed. More significantly, these results experimentally confirm the theoretically expected linear scaling of the ablation- cooled regime to higher average powers without sacrificing efficiency, which implies that further scaling is possible with further increases in laser power and scanning speeds. (C) 2018 Optical Society of America