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。

In past decades, multi-wavelength lasers have attracted much attention due to their wide applications in many fields. In this paper, we demonstrate a multi-wavelength random fiber laser with customizable spectra enabled by an acousto–optic tunable filter. The operating wavelength range can be tuned from 1114.5 to 1132.5 nm with a maximal output power of 5.55 W, and spectral channel tuning can also be realized with a maximal number of five. The effect of gain competition and the interaction between Raman gain and insertion loss are also analyzed. Furthermore, the output spectra can be ordered by radiating appropriate radio frequency signals to the acousto–optic tunable filter. This work may provide a reference for agile shape spectrum generation and promote multi-wavelength random fiber laser practicability in sensing, telecommunications, and precise spectroscopy.

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.

Temporal intensity fluctuation is one of the inherent features of fiber lasers. When utilizing the fiber lasers to pump a random Raman fiber laser (RRFL), the intensity fluctuation transfer from the pump to the random lasing could affect the output performance significantly. In this paper, we comprehensively compared the spectral, temporal, and power characteristics of an RRFL pumped by two different fiber lasers—a temporally unstable fiber oscillator and a temporally stable amplified spontaneous emission (ASE) source. Owing to less impact of the intensity fluctuation transfer, the ASE source-pumped RRFL shows ∼45.3% higher maximum output power, higher spectral purity (>99.9%) and optical signal-to-noise ratio (>40dB), weaker spectral broadening, and more stable temporal behavior compared to the fiber oscillator-pumped RRFL. Furthermore, based on the temporal-spatial-coupled Raman equations and the generalized nonlinear Schrödinger equations, we numerically revealed the impact of the pump intensity fluctuations on the output characteristics of RRFLs, and found that the temporal walk-off effect played an important role in the dynamics of intensity fluctuation transfer. This work may provide a reference for designing and implementing high-performance RRFLs and promote their practicability in sensing, telecommunications, and high-power applications.

光谱灵活可调的高功率光纤激光在光谱合束、光声光谱检测和非线性频率变换等方面具有独特优势，近年来受到国内外研究人员的广泛关注。基于光谱灵活可调的超荧光光纤种子源，通过主振荡功率放大器结构实现了光谱中心波长1065～1085 nm可调谐、3 dB线宽2.4～13.8 nm可调谐的3 kW光纤激光输出。