2 μm ultra-narrow linewidth fiber laser achieves 1 kW near-diffraction-limited output
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摘要: 2 μm波段光纤激光广泛应用于生物医学、环境监测、非线性频率转换，以及激光雷达和激光通信领域，备受研究人员关注。然而，该波段的激光器功率提升面临着低量子效率、高热负载和部分非线性效应的限制。基于反转概率调谐序列的高阶相位调制技术以抑制SBS效应、多级链路自动反馈的信号激光时域稳定控制技术以提升SRS阈值，以及光纤基横模纯化技术以控制光束质量，采用两级主放大结构，在1 950 nm波长实现了1 kW窄线宽近衍射极限输出，光光转换效率达55.6%，线宽3.8 GHz，光束质量M2约1.2，在最高功率时无横向模式不稳定效应。Abstract: Fiber lasers in the 2 μm band are widely applicated in biomedicine, environmental monitoring, nonlinear frequency conversion, as well as in laser radar and laser communications. However, the power scaling of lasers in this band are limited by low quantum efficiency, high thermal loading, and several nonlinear effect. In this study, we propose a higher-order phase modulation technique based on inverted probability tuning sequences to suppress the SBS effect, a signal laser time-domain stabilization control technique with multi-stage link auto-feedback to enhance the SRS threshold, and a fiber-based transverse-mode purification technique to control the beam quality. Finally, a two-stage main amplification structure is used to achieve an ultra-narrow linewidth near-diffraction-limited output of 1 kW at 1 950 nm, with an optical-to-optical conversion efficiency of 55.6%, linewidth of 3.8 GHz, beam quality M2 factor of about 1.2, and no transversemode instability effect.
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Key words:
- fiber laser /
- MOPA amplification /
- thulium-doped fiber laser /
- mode instability /
- quantum loss
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图 1 2 μm千瓦光纤激光器光路结构示意图
Figure 1. Schematic diagram of the optical path structure of a 2 μm kW fiber laser
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