In this paper, an all-fiberized and narrow-linewidth 5 kW power-level fiber amplifier is presented. The laser is achieved based on the master oscillator power amplification configuration, in which the phase-modulated single-frequency laser is applied as the seed laser and a bidirectional pumping configuration is applied in the power amplifier. The stimulated Brillouin scattering, stimulated Raman scattering, and transverse mode instability effects are all effectively suppressed in the experiment. Consequently, the output power is scaled up to 4.92 kW with a slope efficiency of as high as approximately 80%. The 3-dB spectral width is about 0.59 nm, and the beam quality is measured to be M2∼1.22 at maximum output power. Furthermore, we have also conducted a detailed spectral analysis on the spectral width of the signal laser, which reveals that the spectral wing broadening phenomenon could lead to the obvious decrease of the spectral purity at certain output power. Overall, this work could provide a reference for obtaining and optimizing high-power narrow-linewidth fiber lasers.

中文翻译：

---

基于双向泵浦配置的全光纤窄线宽5 kW功率级光纤放大器

本文介绍了一种全光纤窄线宽5 kW功率级光纤放大器。该激光器是基于主振荡器功率放大配置实现的，其中相位调制单频激光器作为种子激光器，功率放大器采用双向泵浦配置。受激布里渊散射、受激拉曼散射和横模不稳定性效应均在实验中得到有效抑制。因此，输出功率扩大到 4.92 kW，斜率效率高达约 80%。3-dB 谱宽约为 0.59 nm，测量光束质量为米2在最大输出功率下约为 1.22。此外，我们还对信号激光器的光谱宽度进行了详细的光谱分析，发现光谱翼展宽现象会导致在一定输出功率下光谱纯度明显下降。总体而言，该工作可为获得和优化高功率窄线宽光纤激光器提供参考。