Spectroscopy of Ho3+-doped fluoride glasses for green double-clad fiber lasers

Abstract

Holmium ions (Ho3+) are attractive for generation of green emission according to the 5F4+ 5S2 → 5 I8 transition. We report on the assessment of the potential of Ho3+ -doped fluoride glasses for green fiber lasers exploiting the double-clad fiber geometry. ZBLAN glasses doped with HoF3 (0.1 – 0.9 mol%) were studied. The absorption cross-section for the 5 I8 → 5F1+ 5G6 transition is 1.75×10-20 cm2 at 448.5 nm. Under excitation in the blue, the glasses exhibit intense green luminescence. The stimulated-emission cross-section for the 5F4+ 5S2 → 5 I8 transition is 0.67×10-20 cm2 at 549 nm. With increasing the HoF3 doping level, the luminescence lifetime of the 5F4+ 5S2 states slowly decreases in the range of 291 – 180 μs. The output performance of a diode-pumped green Ho fiber laser was simulated for a fiber geometry with a double D-shaped inner cladding. The variable parameters were the HoF3 doping …