All-Fiber 1.5-Kw-Class Single-Mode Yb-Doped Polarization-Maintaining Fiber Laser With 10 Ghz Linewidth

In this paper, we have studied the characteristics of stimulated Brillouin scattering (SBS) and mode instability (MI) in a ytterbium-doped polarization-maintaining fiber laser with master oscillator power amplifier configuration. We measured the laser output power and back-reflection spectrum for a variety of ytterbium-doped fibers and seed lights, to investigate the power-scaling limits of fiber lasers. By optimizing the laser structure, we demonstrated an all-fiber high-power polarization-maintaining fiber laser with near-diffraction-limited beam quality. The output power of 1.5 kW was achieved with a linewidth of 10 GHz, generated by pseudo-random binary sequence (PRBS) phase modulation. The beam quality M-2 was about 1.15 at the maximum output power. The polarization extinction ratio (PER) was greater than 17 dB.