Guided blue and green upconversion fluorescence in an erbium-and-ytterbium-containing silicate glass

We report the observation of upconversion fluorescence in an erbium/ytterbium-doped silicate glass. Although upconversion fluorescence has previously been observed in rare-earth doped fluoride glasses, 1,2 and recently in gallate and tellurite glasses, 3 it has generally been believed that silicate glasses are unsuitable for upconversion because of large nonradiative transition probabilities between adjacent energy levels, which are associated with their higher energy phonon spectra. However, we find that the high local intensity of pump power that can be obtained in a waveguide makes upconversion possible in this glass.