Highly-efficient laser ablation of copper by bursts of ultrashort tuneable (fs-ps) pulses

Ultrashort pulse laser, capable of varying pulse duration between 210 fs and 10 ps and producing a burst of pulses with an intra-burst pulse repetition rate of 64.5 MHz (time distance between pulses 15.5 ns), was used to investigate the ablation efficiency of the copper. The study on ablation efficiency was done for various numbers of pulses per burst between 1 and 40. The increase in the ablation efficiency by 20% for 3 pulses per burst compared to a non-burst regime was observed. The comparison was made between the beam-size optimised regimes. Therefore, the real advantage of the burst regime was demonstrated. To the best of our knowledge, we report the highest laser milling ablation efficiency of copper of 4.84 µm(3)/µJ by ultrashort pulses at ~1 µm optical wavelength.