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

Abstract

Over the past few decades, significant advancements have been made in the development of 3 μm fiber lasers utilizing Ho3+/Pr3+ doped fluoride fiber, particularly in terms of slope efficiency and output power. While achieving an efficiency of ∼15 % for the 3 μm laser in AlF3 fiber with a Ho3+/Pr3+ 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 Ho3+/Pr3+ doping ratio on 3 μm laser efficiency. We conducted experiments on Ho3+/Pr3+ co-doped glass and fiber with doping ratios ranging from 1:0.01 to 1:1. Luminescence decay lifetime tests of the Ho3+: 5I6 and 5I7 energy levels in the Ho3+/Pr3+ doped AlF3 glass samples revealed the primary energy transfer progress that affected the 3 μm laser efficiency. When pumped by a 1150 nm Raman fiber laser, a maximum slope efficiency of 29.3 % at 3 μm was obtained in a 1mol%Ho3+/0.6mol%Pr3+ co-doped AlF3 Fiber.