High-power single-frequency pulsed fiber MOPA via SPM suppression based on a triangular pulse

In this work, we demonstrate a high-power single-frequency nanosecond fiber master oscillator power amplifier (MOPA) at 1 μm with near transform-limited narrow spectral linewidth. The seed laser pulses were shaped to triangle for the purpose of suppressing the linewidth broadening induced by self-phase modulation (SPM). A tapered Yb-doped active fiber was used to enhance the stimulated Brillouin scattering (SBS) threshold. A high peak power of 31.4 kW with a narrow linewidth of 63 MHz, which was near the transform limit of the 8-ns triangle-shaped pulse, was achieved at a pulse repetition frequency of 20 kHz. No evident pulse distortion was observed at high-power levels. The results show that the triangle-shaped pulse is a promising technique for high-power single-frequency nanosecond pulsed fiber lasers with narrow spectral linewidth.