In this Letter, we report a high-power narrow-linewidth Yb-Raman fiber amplifier with a high second-order Raman threshold and high intensity stability. By employing two temporally stable seed lasers, over 2 kW output power at 1120 nm is achieved at a pump power of 2.6 kW with an optical-to-optical efficiency of 76.3%. The 3 dB linewidth of the 1120 nm Raman-signal laser varies slightly from 0.41 nm to 0.53 nm, and the power ratio of the second-order Raman Stokes light is only about ${-}{46.3}\;{\rm{dB}}$ at the output power of 2 kW. The results further confirm that the technique of employing temporally stable seed lasers is superior to the power scaling of narrow-linewidth Yb-Raman fiber amplifiers. To the best of our knowledge, it is the first demonstration of an over 2 kW narrow-linewidth fiber laser operating at 1120 nm.

中文翻译：

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2 kW窄线宽Yb-拉曼光纤放大器

在这封信中，我们报告了具有高二阶拉曼阈值和高强度稳定性的高功率窄线宽Yb-拉曼光纤放大器。通过使用两个暂时稳定的种子激光器，以2.6 kW的泵浦功率实现了1120 nm处超过2 kW的输出功率，光-光效率为76.3％。1120 nm拉曼信号激光器的3 dB线宽从0.41 nm到0.53 nm略有变化，二阶拉曼斯托克斯光的功率比仅约为$ {-} {46.3} \; {\ rm {dB }} $在2 kW的输出功率下。结果进一步证实，使用时间稳定的种子激光器的技术优于窄线宽Yb-拉曼光纤放大器的功率缩放。据我们所知，这是首次展示了工作在1120 nm的2 kW以上窄线宽光纤激光器。