Femtosecond 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 an 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) regimes. 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 similar to 1 mu m optical wavelength: 8.8 mu m(3)/mu J for copper drilling, 5.6 mu m(3)/mu J for copper milling, and 6.9 mu m(3)/mu J 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. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement