Mid-infrared emission in Tb^3+-doped selenide glass fiber

The mid-infrared (MIR) emission behavior of Tb 3 -doped Ge-As-Ga-Se bulk glasses (500, 1000, and 1500 ppmw Tb 3 ) and unstructured fiber (500 ppmw Tb 3 ) is investigated when pumping at 2.013 μm.A broad emission band is observed at 4.3-6.0μm corresponding to 7 F 5 → 7 F 6 , with an observed emission lifetime of 12.9 ms at 4.7 μm.The 7 F 4 level is depopulated nonradiatively and so it is proposed that Tb 3 -doped Ge-As-Ga-Se fiber may operate as a quasi-three-level MIR fiber laser.Underlying glass-impurity vibrational absorption bands are numerically removed to give the true Tb 3 absorption cross section, as required for Judd-Ofelt (J-O) analysis.Radiative transition rates calculated from J-O theory are compared with measured lifetimes.A numerical model of the three-level Tb 3 -doped fiber laser is developed for Tb 3 doping of 8.25 × 10 24 ions m -3 (i.e., 500 ppmw) and dependence of laser performance on fiber length, output coupler reflectivity, pump wavelength, signal wavelength, and fiber background loss is calculated.Results indicate the feasibility of an efficient three-level MIR fiber laser operating within 4.5-5.3μm, pumped at either 2.013 or 2.95 μm.