Novel ultrafast laser ablation by bibursts in the MHz and GHz pulse repetition rates

Here, to the best of our knowledge, for the first time we report the in-depth experimental study of high ultrafast laser ablation efficiency for processing of copper and steel with single-pulses, MHz-, GHz- and burst in the burst (biburst) regime. The comparison of burst, biburst, and single-pulse ablation efficiencies was performed for beam-size-optimised regimes, showing the real advantages and disadvantages of milling and drilling processing approaches. Highly-efficient ultrashort pulse laser processing was achieved for ~1 um optical wavelength: 8.8 um3/uJ for copper drilling, 5.6 um3/uJ for copper milling, and 6.9 um3/uJ for steel milling. We believe that the huge experimental data collected in this study will serve well for the better understanding of laser burst-matter interaction and theoretical modelling.