Efficient 2.8-µm Er-doped all-fiber laser based on a low optical feedback cavity

Mid-infrared (mid-IR) fiber lasers have faced significant challenges in achieving all-fiberized structure with high efficiency and high output power due to the limitations of conventional cavity designs. In this paper, we introduce what we believe to be a novel 2.8 µm all-fiber laser configuration with a low optical feedback linear cavity, effectively eliminating the need for traditional high-reflector components. This approach simplifies the design of mid-IR erbium fiber lasers, offering enhanced flexibility in design and application. Experimentally, we demonstrate a 2.8 µm Er-doped fluoride fiber laser with a maximum output power of 12.5 W and an optical efficiency of 22.1%. Additionally, we present a numerical model to analyze the laser power behavior and determine the cavity optical feedback through a control experiment. Methods for stabilizing the laser wavelength are also discussed. This work provides a practical solution for developing high-efficiency, high-power all-fiber mid-IR lasers with simplified configurations, paving the way for their broader applications in diverse fields.