Optical spectroscopy of erbium-doped fluorohafnate glasses for 2.8 µm lasers

Fluorohafnate glasses (HfF4–BaF2–LaF3–AlF3–NaF) doped with erbium ions were fabricated by the melt-quenching technique at 870 °C in argon atmosphere, and their spectroscopic properties were studied. The glasses exhibit a low phonon energy (575 cm-1), a broadband mid-infrared emission (stimulated-emission cross-section: 0.51×10-20 cm2 at 2.76 µm), and long luminescence lifetimes of the 4I11/2 and 4I13/2 manifolds making them attractive for 2.8-µm laser sources.