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Simultaneous material processing by picosecond-pulse bursts and nanosecond pulses arbitrarily generated by a directly modulated laser diode system

We report a directly modulated laser diode system capable of generating picosecond-pulse bursts and nanosecond pulses simultaneously. A generated pulse shape can be arbitrary controlled with a temporal resolution of 1 ns and wavelength of 1064 nm. A two-stage Nd:YVO4 amplifier boosts the pulse energy to hundreds of microjoules to process JIS 304 stainless steel. Characterization of processed holes irradiated by different pulse durations and shapes reveals that the ablation efficiencies with the nanosecond pulses are two times higher than those with the picosecond-pulse bursts. A clear hole with a taper angle of 1.5° is realized by the picosecond-pulse bursts with a 10-ns pulse interval. The combination of pulses with large differences in timescales offers an efficient production line with a single laser system.