Efficiency improvement for Ho3+/Pr3+co-doped 3 μm fiber laser in AlF3-based glass fiber

Over the past few decades, significant advancements have been made in the development of 3 mu m fiber lasers utilizing Ho 3+ /Pr 3+ doped fluoride fiber, particularly in terms of slope efficiency and output power. While achieving an efficiency of -15 % for the 3 mu m laser in AlF 3 fiber with a Ho 3+ /Pr 3+ doping ratio of -10:1, further improvements are necessary to approach the Stokes efficiency limit of -40 %. Our study focused on the influence of the Ho 3+ /Pr 3+ doping ratio on 3 mu m laser efficiency. We conducted experiments on Ho 3+ /Pr 3+ co-doped glass and fiber with doping ratios ranging from 1:0.01 to 1:1. Luminescence decay lifetime tests of the Ho 3+ : 5 I 6 and 5 I 7 energy levels in the Ho 3+ /Pr 3+ doped AlF 3 glass samples revealed the primary energy transfer progress that affected the 3 mu m laser efficiency. When pumped by a 1150 nm Raman fiber laser, a maximum slope efficiency of 29.3 % at 3 mu m was obtained in a 1mol%Ho 3+ /0.6mol%Pr 3+ co-doped AlF 3 Fiber.