Numerical modeling and optimization of mid-infrared random distributed feedback fiber lasers

For the first time ever, we numerically demonstrated a random distributed feedback fiber laser in the mid-infrared regime by using fluoride fibers pumped at 2.05 µm. The relation of the total loss for the Rayleigh scattering coefficient in fluoride fibers at the 2.05 µm wavelength band was derived theoretically. The numerical model was established to optimize the fiber length and pump power to maximize the first-Stokes output power. A fiber length of 68 m with a maximum available 200 W pump power is recommended to obtain a relatively large output power. The maximum obtained first-Stokes power was 137.6 W, and the conversion efficiency was 71%. In addition, the influences of the reflectance of the fiber Bragg grating on the output properties were also investigated. (paper)