简单MOPA结构窄线宽激光突破5 kW近单模输出

高功率窄线宽光纤激光器在非线性频率转换、光谱合成以及相干合成等领域有着重要的应用前景。本文基于自研的复合腔结构窄线宽振荡器作为种子，采用单级主振荡功率放大技术（MOPA），实现了5 kW高效率的近单模窄谱激光输出。通过优化振荡器的时序特性和放大级结构，受激拉曼散射、光谱展宽和热致模式不稳定效应得到综合抑制。在最高功率时，信号光的3 dB和20 dB线宽分别为0.48 nm和2.1 nm，放大器的斜率效率约为86.1%，拉曼抑制比为28.3 dB，光束质量M2约1.35。本研究工作对于高功率窄线宽光纤激光的发展和研究具有重要的指导意义。

5 kW near single mode output of narrow linewidth laser with simple MOPA structure

High-power narrow-linewidth fiber lasers are highly desired for nonlinear frequency conversion, spectral combination, and coherent combination. In this work, a 5 kW near single mode narrow-linewidth fiber laser system is established based on a composite fiber oscillator seed. By optimizing temporal characteristic of seed and structure of amplifier, the stimulated Raman scattering, spectral broadening, and transverse mode instability effects are suppressed comprehensively. Consequently, the output power is scaled up to 5 kW with a slope efficiency as high as approximately 86.1%. The peak signal to noise ratio is about 28.3 dB compared with the Raman Stokes light. The 3 dB and 20 dB linewidths are 0.48 nm and 2.1 nm, respectively. The beam quality (M2 factor) is about 1.35. This work shows a amplification potential of narrow-linewidth fiber lasers based on such a simple structure.