White light generation by frequency upconversion in Tm3+/Ho3+/Yb3+-codoped fluorolead germanate glass

White light was produced exploiting an additive synthesis of red, green, and blue fluorescence through frequency upconversion in fluorolead-germanate glass codoped with Ho3+, Tm3+, and Yb3+. The 475, 540, and 650 nm signals were, respectively, assigned to thulium ((1)G(4)-H-3(6)) and holmium (S-5(2);F-5(4))-> I-5(8) and F-5(5)-> I-5(8), excited via energy tranfer from ytterbium. The dopant concentrations were adjusted, yielding the emission of a wide color gamut in the visible spectrum and the production of white light using excitation at 975 nm. The spectral positions and purity (blue, 97%; green, 100%; red, 95%) of the three colors produced CIE-X=0.3438 and CIE-Y=0.3639 coordinates. (c) 2007 American Institute of Physics.