In this paper, we report a high-power single-frequency all-fiber amplifier at 1064 nm based on cascaded hybrid active fibers. The cascaded gain fiber design, where a piece of active fiber with lower dopant concentration is spliced before the highly doped gain fiber, is proposed to effectively alleviate the thermal loads of high-power amplifier. By virtue of hybrid pump at 976 nm and 915 nm to increase the threshold of mode instability (MI) effect, an output power of 435 W is achieved from the Yb${}^{3+}$-doped fiber with large core diameter of 30 $\mathrm{\mu }$m. The beam quality is well maintained with a M² of 1.40 even at the maximum laser power.

中文翻译：

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基于级联混合有源光纤的 1064 nm 435 W 单频全光纤放大器

在本文中，我们报告了一种基于级联混合有源光纤的 1064 nm 高功率单频全光纤放大器。级联增益光纤设计，在高掺杂增益光纤之前拼接一根低掺杂浓度的有源光纤，可有效减轻高功率放大器的热负荷。凭借 976 nm 和 915 nm 的混合泵浦增加模式不稳定 (MI) 效应的阈值，Yb 实现了 435 W 的输出功率${}^{3+}$大纤芯直径 30 的掺杂光纤 $\mathrm{\mu }$米。即使在最大激光功率下，光束质量也能保持良好，M ²为 1.40。