All-fiber narrow line 1.6 mJ/9 ns high-power MOPA system with spun Yb-doped tapered fiber

High-energy, narrow-linewidth pulsed fiber lasers are fundamentally limited by nonlinear effects, particularly stimulated Brillouin scattering, which constrains power scaling. Here, we demonstrate a master-oscillator power-amplifier system that incorporates a spun large-mode-area tapered double-clad fiber gain module to effectively suppress stimulated Brillouin scattering without the need for external spectral broadening techniques. The system produces 9 ns pulses at a 100 kHz repetition rate, achieving pulse energies of 1.6 mJ, average powers of 160 W, and peak powers up to 180 kW with near-diffraction-limited beam quality. The amplified pulses exhibit a linewidth of ~115 MHz, highlighting the potential of spun tapered double-clad fiber for high-power, narrow-linewidth amplifiers for applications demanding both high temporal and spatial coherence.