Ma Pengfei, Miao Yu, Liu Wei, Meng Daren, Zhou Pu
Opt Lett. 2020 Apr 1;45(7):1974-1977. doi: 10.1364/OL.387151.
By focusing on a typical emitting wavelength of 1120 nm as an example, we present the first, to the best of our knowledge, demonstration of a high-efficiency, narrow-linewidth kilowatt-level all-fiber amplifier based on hybrid ytterbium-Raman (Yb-Raman) gains. Notably, two temporally stable, phase-modulated single-frequency lasers operating at 1064 nm and 1120 nm, respectively, were applied in the fiber amplifier, to simultaneously alleviate the spectral broadening of the 1120 nm signal laser and suppress the stimulated Brillouin scattering effect. An over 1 kW narrow-linewidth 1120 nm signal laser was obtained with slope efficiency of ${\sim}{77}% $∼77% and beam quality of ${\rm M}_x^2\sim {1.25}$Mx2∼1.25, ${\rm M}_y^2 \sim {1.17}$My2∼1.17. The amplified spontaneous emission (ASE) noise in the fiber amplifier was effectively suppressed by incorporating an ASE-filtering system between the seed laser and the main amplifier. Furthermore, the experimental results demonstrate that the spectral linewidth broadening effect is tightly related to the injected power ratios between the two seed lasers. Overall, this setup could provide a reference on obtaining and optimizing high-power narrow-linewidth fiber lasers operating in the long wavelength extreme of the Yb gain spectrum.
以1120 nm这一典型发射波长为例，据我们所知，我们首次展示了一种基于镱 - 拉曼（Yb - Raman）混合增益的高效、窄线宽千瓦级全光纤放大器。值得注意的是，分别在1064 nm和1120 nm波长工作的两个时间稳定、相位调制的单频激光器被应用于光纤放大器中，以同时减轻1120 nm信号激光的光谱展宽并抑制受激布里渊散射效应。获得了超过1 kW的窄线宽1120 nm信号激光，其斜率效率约为77%，光束质量为$M_x^2\sim1.25$，$M_y^2\sim1.17$。通过在种子激光器和主放大器之间加入一个ASE滤波系统，有效抑制了光纤放大器中的放大自发辐射（ASE）噪声。此外，实验结果表明，光谱线宽展宽效应与两个种子激光器之间的注入功率比密切相关。总体而言，该装置可为在镱增益谱长波长端获得和优化高功率窄线宽光纤激光器提供参考。
