Ultrafast laser ablation by bi-bursts in MHz and GHz pulse repetition rate

Femtosecond laser (Pharos, Light Conversion) with the possibility to produce bi-burst pulses with a repetition rate of 64.5 MHz or/and 4.88 GHz was used to structure copper and steel samples. Ablation efficiency and quality were studied by varying number of pulses per burst in conventional burst regimes and in the bi-burst mode. The comparison of burst, bi-burst and single-pulse ablation efficiencies was done for beam-size-optimised regimes, showing the real advantages and disadvantages of milling and drilling processing approaches.