Arbitrarily-shaped bursts of picosecond pulses from a fiber laser source for high-throughput applications

摘要

Increasing the ablation efficiency of picosecond laser sources can be performed by bunching pulses in bursts and benefit from heat accumulation effects in the target. Pulsed fiber lasers are well suited for such a regime of operation, as the single pulse energy in a fiber is limited by the onset of nonlinear effects (SPM, SRS). Increasing the number of pulses to form a burst of pulses allows for average power scaling of picosecond fiber lasers. We are presenting in this paper a high-power fiber laser emitting arbitrarily-shaped bursts of picosecond pulses at 20 W of average output power. Burst duration can be varied from 2.5 ns to 80 ns. The burst repetition rate is externally triggered and can be varied from 100 kHz to 1 MHz. The single pulse duration is 60 ps and the repetition rate within a burst is 1.8 GHz. The output beam is linearly polarized (PER > 20 dB) and its M2 value is smaller than 1.15. The laser source has a tunable central wavelength around 1064 run and a spectral linewidth compatible with frequency conversion. Conversion efficiency higher than 60% has been obtained at 10 W of 1064-nm output power.