Experimental and numerical investigation of mid-infrared laser in Pr³⁺-doped chalcogenide fiber

We report on a chalcogenide glass fiber doped with Pr³⁺ that can be used for commercialized 1.5-μm and 2-μm laser excitations by emitting broadband 3 μm-5.5 μm fluorescence, which is extruded into a preform and then drawn into a step-index fiber. The spectroscopic properties of the fiber and glass are reported, and the mid-infrared fiber lasers are also numerically investigated. Cascade lasing is employed to increase the inversion population of the upper laser level. The particle swarm approach is applied to optimize the fiber laser parameters. The output power can reach 1.28 W at 4.89-μm wavelength, with a pump power of 5 W, excitation wavelength at 2.04 μm, Pr³⁺ ion concentration at 4.22×10²⁵ ions/m³, fiber length at 0.94 m, and fiber background loss at 3 dB/m.