Upconversion fluorescence of tellurite glasses doped with rare earths

Ternary tellurite glasses were prepared by a conventional quenching method in the system TeO//2-LiO//0//.//5-YO//1//.//5. IR spectra reveal that the glasses contain the following polyhedra: deformed TeO//6 groups, TeO//4-trigonal bipyramids, TeO//3-trigonal pyramids, or combinations of these polyhedra. The highly addition of glass-network modifiers, especially Li** plus ion, leads to a collapse of polyhedra networks. The intense emission peak, due to the transition**4S//3/////2- **4I//1//5/////2, was found at 546 nm in tellurite glasses doped with Er**3** plus under 378 nm and 973 nm excitations at the room temperature. Upon excitation at 973 nm, the emission shows a typical upconversion characteristic, indicating the quadratic profiles of the emission intensities against the exciting powders. The emission intensities tend to be dependent upon 378 nm excitation, but independent of Er**3** plus concentration upon 973 nm excitation. The excitation and emission involve two photons process through the**4I//1//1/////2 level of Er**3** plus ion. Upconversion fluorescence is, also, enhanced at 547 nm by the supplementary doping with Yb**3** plus ion. (Author abstract) 9 Refs.

Endo, Tadashi Tanaka, Kuniharu Takizawa, Hirotsugu Shimada, Masahiko