Upconversion Fluorescence of Tellurite Glasses Doped with Rare Earths

Ternary tellurite glasses were prepared by a conventional quenching method in the system TeO₂-LiO_0.5-YO_1.5⋅IR spectra reveal that the glasses contain the following polyhedra: deformed TeO₆ groups, TeO₄-trigonal bipyramids, TeO₃-trigonal pyramids, or combinations of these polyhedra. The highly addition of glass-network modifiers, especially Li⁺ion, leads to a collapse of polyhedra networks. The intense emission peak, due to the transition ⁴S_3/2-⁴I_15/2, was found at 546 nm in tellurite glasses doped with Er³⁺ under 378 nm and 973 nm excitations at the room temperature. Upon excitation at 973nm, the emission shows a typical upconversion characteristic, indicating the quadratic profiles of the emission intensities against the exciting powers. The emission intensities tend to be dependent upon 378nm excitation, but independent of Er³⁺ concentration upon 973 nm excitation. The excitation and emission involve two photons process through the ⁴I_11/2 level of Er³⁺ion. Up conversion fluorescence is, also, enhanced at 547nm by the supplementary doping with Yb³⁺ion.