High-beam-quality single-frequency 10-mJ nanosecond fiber and a solid-state hybrid laser front-end system at a 1-kHz repetition rate

A compact single-frequency nanosecond fiber & solid-state hybrid laser system at 1030 nm is presented. The seed source, a continuous wave distributed feedback (DFB) laser diode, was first externally modulated with a repetition rate of 1.5 MHz and a pulse duration of 10 ns, whose repetition rate was further lowered to 1 kHz by a pulse picker. Afterwards, three-stage end-pumped Yb:YAG crystal amplifiers were employed for energy scaling. Finally, an average power of 12 W was obtained with a repetition rate of 1 kHz and a linewidth of ∼180 MHz, corresponding to approximately four times the Fourier transform limit (FTL). The beam quality factor (M 2 ) was measured to be 1.18 and 1.20 for the horizontal and vertical directions, respectively. In the future, this high-beam quality front-end laser will be used as the seed source for nanosecond disk laser amplifiers.