In this paper, a cost-effective 50-W-level all-fiber oscillator operating near 980 nm is demonstrated with the 20-μm core-diameter double-cladding Yb-doped fiber (DCYF) firstly, to the best of our knowledge. By using the 15-degree angle-cleaved output fiber end-facet, the record 54.8-W output power is obtained with the slope efficiency about 15.6%. It is revealed that increasing the cleaved angle (or suppressing the optical feedback) of output fiber end-facet should be an effective way to improve the performance of the fiber oscillator. Then, by optimizing the length of DCYF, the slope efficiency is slightly improved to 15.8% because of better suppression of the amplified spontaneous emission (ASE) around 1030 nm. It is also found that the effect of pumping scheme is negligible on the performance of the fiber oscillator. The beam quality is measured and the M² factor is about 2.5. Better beam quality can be expected by lowering the numerical aperture (NA) of the active fiber core. The all-fiber oscillator can provide a well solution for the high-power core-pump source.

在本文中，据我们所知，首先使用 20 μm 芯径双包层掺镱光纤 (DCYF) 演示了一种在 980 nm 附近运行的具有成本效益的 50 W 级全光纤振荡器。通过使用 15 度角切割输出光纤端面，获得了创纪录的 54.8W 输出功率，斜率效率约为 15.6%。结果表明，增加输出光纤端面的解理角（或抑制光反馈）应该是提高光纤振荡器性能的有效途径。然后，通过优化 DCYF 的长度，斜率效率略微提高到 15.8%，因为更好地抑制了 1030 nm 附近的放大自发发射 (ASE)。还发现泵浦方案对光纤振荡器性能的影响可以忽略不计。²因子约为 2.5。通过降低有源光纤纤芯的数值孔径 (NA)，可以获得更好的光束质量。全光纤振荡器可为大功率芯泵源提供良好的解决方案。