量子亏损对高功率光纤激光器内的废热产生和光光转换效率具有重要影响，光纤激光器输出功率的提升过程可以视为不断与量子亏损作斗争的过程。文中梳理了近年来1 μm波段低量子亏损光纤激光的重要进展，重点介绍了稀土掺杂增益和拉曼增益两种体制的光纤激光器在实现低量子亏损输出方面的相关工作。在稀土掺杂光纤激光器中，采用级联泵浦、多组分掺杂、强泵浦等技术可降低激光器的量子亏损，其中量子亏损≤1%的掺镱光纤激光器已实现400 mW功率输出。在拉曼光纤激光器中，通过采用特殊掺杂、泵浦光谱调控、增益竞争抑制等技术，量子亏损≤1%的拉曼光纤激光器已实现百瓦级功率输出，并成功验证包层泵浦方案的可行性，表明其在实现高功率低量子亏损输出方面具有重要潜力。

The quantum defect (QD) is an important issue that demands prompt attention in high-power fiber lasers. A large QD may aggravate the thermal load in the laser, which would impact the frequency, amplitude noise and mode stability, and threaten the security of the high-power laser system. Here, we propose and demonstrate a cladding-pumped Raman fiber laser (RFL) with QD of less than 1%. Using the Raman gain of the boson peak in a phosphorus-doped fiber to enable the cladding pump, the QD is reduced to as low as 0.78% with a 23.7 W output power. To our knowledge, this is the lowest QD ever reported in a cladding-pumped RFL. Furthermore, the output power can be scaled to 47.7 W with a QD of 1.29%. This work not only offers a preliminary platform for the realization of high-power low-QD fiber lasers, but also proves the great potential of low-QD fiber lasers in power scaling.

2010年模式不稳定现象首次报道，开启了光纤激光与废热的斗争史。回顾了10年来模式不稳定现象的研究进展，概述了光纤激光模式不稳定物理表征、基本原理、理论研究、影响因素和抑制策略等，介绍了高功率光纤激光在模式不稳定抑制方面取得的最新成果，展望了高功率光纤激光模式不稳定研究的未来发展，对光纤激光模式不稳定未来可能的研究方向进行了展望。