We demonstrate new, large-mode area (LMA) gain fibers with ∼25 µm mode-field diameter, and increased higher-order mode loss that enable diffraction limited, pulsed fiber lasers operating at high average power with high pulse energy. We achieved 1.6 mJ, ns pulses, with 1.2 kW average power and 370 kW peak power in one of the new Yb-doped gain fibers. In a second, higher absorption fiber, we demonstrate 2 mJ pulse energy with peak power of >420 kW at an average power of 660 W. To the best of our knowledge these are the highest demonstrated energies, powers and peak powers for any nanosecond diffraction-limited, all-fiber laser. The TMI thresholds of two of these fibers were measured to be 1.8 kW and 1 kW respectively.

中文翻译：

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LMA 光纤具有更高的高阶模式损耗，适用于高平均功率、脉冲、衍射极限激光器

我们展示了新型大模面积 (LMA) 增益光纤，模场直径约为 25 µm，并增加了高阶模损耗，使衍射受限的脉冲光纤激光器能够在高平均功率和高脉冲能量下工作。我们在一种新型掺镱增益光纤中实现了 1.6 mJ、ns 脉冲、1.2 kW 平均功率和 370 kW 峰值功率。在第二个吸收率更高的光纤中，我们展示了 2 mJ 脉冲能量，峰值功率 >420 kW，平均功率为 660 W。据我们所知，这些是任何纳秒衍射所展示的最高能量、功率和峰值功率-有限的全光纤激光器。其中两根光纤的 TMI 阈值经测量分别为 1.8 kW 和 1 kW。