In this work, high-power tandem-pumped random fiber lasers are investigated in detail. A 6.5 W random fiber laser seed centered at 1070 nm with a half-open cavity structure was built. Boosted by two amplifier stages, the random fiber laser achieved a power of several kilowatts. Stimulated Raman scattering (SRS) mitigation is challenging in tandem-pumped fiber lasers. To suppress SRS, several methods were applied, including avoiding external feedback in the oscillator stage, incorporating a high core/cladding diameter ratio gain fiber, and using a band pass filter (BPF) to mitigate Raman noise. The latter proved to be the most effective method; therefore, SRS mitigation without and with a BPF was investigated at 3.5 kW, leading to suppression ratios rising from 14 to 30 dB. By increasing the pump power continuously to 5.6 kW, we realized a record output power of 5.1 kW, corresponding to an SRS suppression ratio of 27 dB. Owing to the high-brightness 1018 nm fiber lasers serving as the pump sources and the high gain coefficient in the second amplifier stage, the entire system demonstrated high efficiency and stability. At the maximum power level, the total optical-to-optical efficiency reached 89.0%. This work offers an economic and practical technique for realizing high-power and high-efficiency random fiber lasers with effective SRS mitigation, while the experimental results suggest the potential for further power scaling.

中文翻译：

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5.1 kW 串联泵浦光纤放大器，由随机光纤激光器引种，具有高抑制受激拉曼散射

在这项工作中，详细研究了高功率串联泵浦随机光纤激光器。构建了一个以 1070 nm 为中心的具有半开腔结构的 6.5 W 随机光纤激光器种子。在两个放大器级的推动下，随机光纤激光器达到了几千瓦的功率。受激拉曼散射 (SRS) 缓解在串联泵浦光纤激光器中具有挑战性。为了抑制 SRS，应用了多种方法，包括避免振荡器阶段的外部反馈、结合高纤芯/包层直径比增益光纤，以及使用带通滤波器 (BPF) 来减轻拉曼噪声。后者被证明是最有效的方法；因此，在 3.5 kW 下研究了没有和有 BPF 的 SRS 抑制，导致抑制比从 14 dB 上升到 30 dB。通过将泵功率连续增加到 5.6 kW，我们实现了 5.1 kW 的创纪录输出功率，对应于 27 dB 的 SRS 抑制比。由于作为泵浦源的高亮度1018 nm光纤激光器和第二级放大级的高增益系数，整个系统表现出高效率和稳定性。在最大功率水平下，总光对光效率达到 89.0%。这项工作为实现具有有效 SRS 抑制的高功率和高效率随机光纤激光器提供了一种经济实用的技术，而实验结果表明了进一步功率缩放的潜力。整个系统表现出高效率和稳定性。在最大功率水平下，总光对光效率达到 89.0%。这项工作为实现具有有效 SRS 抑制的高功率和高效率随机光纤激光器提供了一种经济实用的技术，而实验结果表明了进一步功率缩放的潜力。整个系统表现出高效率和稳定性。在最大功率水平下，总光对光效率达到 89.0%。这项工作为实现具有有效 SRS 抑制的高功率和高效率随机光纤激光器提供了一种经济实用的技术，而实验结果表明了进一步功率缩放的潜力。