Yellow stimulated emission from Dy 3+ -doped silica glass microspheres
Résumé
Dy 3+ -doped silica glass whispering gallery mode microspheres are fabricated by fiber fusion splicing. They present an almost ideal spherical morphology with a radius ranging from 60 to 67 µm, as determined by confocal laser microscopy. The host composition of the microsphere is close to that of the fiber core. The dopant Dy 3+ ions are uniformly distributed across the microsphere, as evidenced by µ-luminescence studies, and present a luminescence lifetime of the 4 F 9/2 state of 514.7 ± 1.1 µs, indicating a weak luminescence quenching. The Dy 3+ -doped glass microspheres were excited via evanescent field coupling using a half-tapered fiber and a blue 450-nm GaN laser diode (direct pumping scheme). The yellow fluorescence of Dy 3+ ions (the 4 F 9/2 → 6 H 13/2 transition) is filtered by the whispering gallery modes (free spectral range: 0.5 nm for 67-µm radius microsphere). The onset of stimulated emission is further observed, highlighting the potential of such microresonators for narrow-linewidth light sources directly emitting visible light.
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