Tb 3+ doped Ga 5 Ge 20 Sb 10 Se 65-x Te x (x = 0-37.5) chalcogenide glasses and fibers for MWIR and LWIR emissions

Chalcogenide glasses with a nominal composition of Ga5Ge20Sb10Se(65-x)Tex (x = 0, 10, 20, 25, 30, 32.5, 35, 37.5) were synthesized. Their physico-chemical properties, glass network structure and optical properties are clearly modified via the substitution of selenium by tellurium. Based on a detailed study of the Ga5Ge20Sb10Se(65-x)Tex bulk glasses properties, the Ga5Ge20Sb10Se45Te20 seleno-telluride glass optimal composition has been selected for fiber drawing. The luminescence properties of Tb3+(500 ppm) doped Ga5Ge20Sb10Se65 and Ga5Ge20Sb10Se45Te20 bulk glasses and fibers were studied. Radiative transitions parameters calculated from the Judd-Ofelt theory are compared to the experimental values. Mid-wavelength infrared emission in the range of 4.3-6.0 µm is attributed to the 7F5→7F6 transition of Tb3+ions with a corresponding experimental lifetime of 8.9 and 7.8 ms for the selenide and seleno-telluride matrix, respectively. The 7F4 → 7F6 emission was recorded at 3.1 µm with a good signal-to-noise ratio, evidencing a rather strong emission from the 7F4 manifold. Finally, although it was expected that the phonon energy will be lower for telluride glasses, selenide glasses are still more suitable for mid-wavelength infrared and long wavelength infrared emissions with well-defined emissions from 3.1 to 8 μm.