Abstract: Mid-infrared (MIR) fiber lasers have significant application value in many fields, such as laser medicine, gas monitoring, and material processing, due to their wavelengths locating in the molecular fingerprint region. Based on an 8°-angle cleaved Er:ZBLAN fiber and a reflective diffraction grating, a continuously wavelength-tunable MIR fiber laser output has been achieved in this work. Under the optimal output condition, the laser exhibits a slope efficiency of 9.86% with a central wavelength of 2780.9 nm. At a low pump power of 0.5 W, the laser achieves wavelength tuning in a range of more than 100 nm. At a pump power of 2 W, the laser wavelength can be continuously tuned from 2708.6 nm to 2850.6 nm by rotating the diffraction grating, with a tuning range of 142 nm, and the maximum output power occurs at the wavelength of 2793.3 nm. In addition, power stability tests at 2714.4 nm, 2793.3 nm, and 2844.1 nm under a pump power of 2 W show that the root mean square error of the output power at the three wavelengths is less than 1% within 2 h, demonstrating excellent stability.

Key words: laser techniques, wavelength-tunable fiber laser, diffraction grating, Er:ZBLAN fiber, midinfrared