The radical suppression of the photodarkening effect and laser performance deterioration via H2 loading were demonstrated in high-power Yb-doped fiber (YDF) amplifiers. The photodarkening loss at equilibrium was 114.4 dB/m at 702 nm in the pristine fiber, while it vanished in the H2-loaded fiber. To obtain a deeper understanding of the impact of photodarkening on laser properties, the evolution of the mode instability threshold and output power in fiber amplifiers was investigated. After pumping for 300 min, the mode instability threshold of the pristine fiber dropped from 770 to 612 W, and the periodic fluctuation of the output power became intense, finally reaching 100 W. To address the detrimental effects originating from photodarkening, H2 loading was applied in contrast experiments. The output power remained stable, and no sign of mode instability was observed in the H2-loaded fiber. Moreover, the transmittance at 638 nm confirmed the absence of the photodarkening effect. The results pave the way for the further development of high-power fiber lasers.

中文翻译：

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H2负载对高功率掺镱光纤放大器光暗效应的有效抑制

在高功率掺镱光纤 (YDF) 放大器中证明了通过 H2 负载对光暗效应和激光器性能恶化的自由基抑制。原始光纤在 702 nm 处的平衡光暗损耗为 114.4 dB/m，而在加载 H2 的光纤中消失。为了更深入地了解光暗化对激光特性的影响，研究了光纤放大器中模式不稳定性阈值和输出功率的演变。泵浦 300 分钟后，原始光纤的模式不稳定阈值从 770 W 下降到 612 W，输出功率的周期性波动变得剧烈，最终达到 100 W。为了解决源自光暗化的不利影响，施加了 H2 负载在对比实验中。输出功率保持稳定，并且在加载 H2 的光纤中没有观察到模式不稳定的迹象。此外，638 nm 处的透射率证实不存在光暗化效应。研究结果为高功率光纤激光器的进一步发展铺平了道路。