Structured active fiber fabrication and characterization of a chemically high-purified Dy3+-doped chalcogenide glass

By conventional melt-quenching techniques, a series of Dy 3+ -doped (0.1 to 1.0 wt%) Ga 5 Ge 20 Sb 15 S 60 bulk glasses were fabricated and their potential for developing mid-infrared fiber laser beyond 4 μm were evaluated, in which the optimal Dy 3+ doping concentration was found to be 0.3 wt% and the largest laser quality factor value ( σ e × τ mea = 2.62 × 10 −23 cm 2 s) among all of the Dy 3+ -doped chalcogenide glass was obtained. On this basis, through using the chemical purification methods with chlorine gas combined with the dynamic distillation process, the high-purity GGSS glasses with low O–H and S–H absorptions were successfully fabricated, which was confirmed by the optimized mid-infrared linear transmittance and improved fluorescent lifetimes of Dy 3+ : 6 H 13/2 , 6 H 11/2 levels. Furthermore, for the first time to the best of our knowledge, the Dy 3+ -doped, single-mode, and double-cladding chalcogenide fibers with the core/cladding ratios of 125:60:11 and 125:66:11.5 were achieved by a multistage rod-in-tube fiber drawing process and extrusion methods, respectively. The GeS 2 -based fiber exhibits excellent transmission performance at 1.0-5.0 μm: 3.0 dB/m at 2.9 μm (O–H), 2.4 dB/m at 4.1 μm (S–H). Combining the advantages of high-purity, high doping concentration and single-mode double-cladding structure, the optimized active fiber should be an ideal efficient and low-threshold medium toward mid-infrared fiber laser beyond 4 μm.