A 376 kW narrow-linewidth pulsed fiber laser based on PRBS

When designing a fiber laser, it is difficult to achieve both narrow linewidth and high power due to nonlinear effects, especially stimulated Brillouin scattering (SBS). However, using the pseudo-random binary sequence (PRBS) phase modulation technique, SBS can be effectively suppressed in narrow-linewidth fiber lasers during amplification. In light of this, we carried out the experimental research described in this paper. First, based on a theoretical analysis, a narrow-linewidth linearly polarized pulsed fiber laser system was designed; then, an experimental platform of a multistage master-oscillator power amplifier (MOPA) structure was constructed, including one-stage continuous optical amplification and four-stage pulsed optical amplification. In our experiments, without phase modulation, a linearly polarized narrow-linewidth fiber laser achieved an average power output of 17 W and a peak power of 188 kW (repetition frequency of 10 kHz, pulse width of 8.5 ns). At this level of power, the spectral signal-to-noise ratio was about 40 dB, and the beam transmission factors in the X and Y directions were 1.14 and 1.11, respectively. Using PRBS phase modulation, a linearly polarized narrow-linewidth pulsed laser achieved an average power output of 30 W and a peak power of 376 kW (repetition frequency of 10 kHz, pulse width of 7.5 ns) at a clock rate of 1.25 GHz. The polarization extinction ratio was greater than 15 dB, the spectral signal-to-noise ratio was greater than 40 dB, and the beam transmission factors in the X and Y directions were 1.18 and 1.12, respectively.