A novel high-power fiber laser oscillator employing a saddle-shaped core ytterbium-doped fiber (SSCYDF) is proposed and demonstrated experimentally. The SSCYDF is designed and fabricated with a long-tapering core (diameter of ~ 30 µm at both ends and ~ 23 µm in the middle) and a constant inner cladding (diameter of ~ 400 µm) in longitudinal dimension. On the one hand, the small core section of the fiber can only support less than two modes, which is helpful for the mitigation of the transverse mode instability. On the other hand, the large core section provides a large mode area for suppression of stimulated Raman scattering. Therefore, this type of laser oscillator holds the potential advantages for both mitigation of transverse mode instability and suppression of stimulated Raman scattering. Based on the homemade SSCYDF, an all-fiber laser oscillator is constructed and investigated by pumping with laser diodes at wavelength of 976 nm and 915 nm, respectively. The maximum output power of 1312 W is achieved in the case of co-pumping at 915 nm. This is the first work, to the best of our knowledge, to validate the feasibility of using saddle-shaped core ytterbium-doped fiber with constant cladding for high-power fiber lasers.

中文翻译：

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一种采用鞍形纤芯掺镱光纤的新型光纤激光振荡器

提出并通过实验证明了一种采用鞍形纤芯掺镱光纤 (SSCYDF) 的新型高功率光纤激光振荡器。SSCYDF 的设计和制造具有长锥形纤芯（两端直径约 30 µm，中间直径约 23 µm）和纵向尺寸恒定的内包层（直径约 400 µm）。一方面，光纤的小纤芯部分只能支持少于两种模式，这有助于缓解横模不稳定性。另一方面，大纤芯截面为抑制受激拉曼散射提供了大模式面积。因此，这种类型的激光振荡器在减轻横向模式不稳定性和抑制受激拉曼散射方面具有潜在优势。基于自制的SSCYDF，通过分别用波长为 976 nm 和 915 nm 的激光二极管泵浦来构建和研究全光纤激光振荡器。在 915 nm 共泵浦的情况下，实现了 1312 W 的最大输出功率。据我们所知，这是第一项工作，以验证使用具有恒定包层的鞍形纤芯掺镱光纤用于高功率光纤激光器的可行性。