Blue-green cooperative upconverted luminescence and radiative energy transfer in Yb3+-doped tungsten tellurite glass

Ytterbium-doped tungsten tellurite glasses have been prepared and studied their cooperative upconverted luminescence and radiative energy transfer properties. In a 3.0 mol% Yb2O3-doped glass, near-infrared emission band is peaked at around 977 nm with a full width at half maximum of around 15 nm. This glass emits blue-green upconverted emission under 980 nm excitation due to cooperative processes involving two interacting Yb3+ ions. The upconverted emission band is centered at around 502 nm with a bandwidth of around 45 nm. Power dependence of cooperative emission intensity and the temporal evolutions of the near-infrared and blue-green emissions confirm the presence of cooperative luminescence. Photoluminescence and lifetimes have been measured by moving the laser excitation from one edge of the sample and found that radiative energy transfer is predominant in 3.0 mol% of Yb2O3-doped glass. The absorption coefficient obtained from absorption spectrum is in good agreement with that obtained by fitting the curve of luminescence intensity versus distance from the edge of the sample.