SPECTROSCOPIC STUDIES OF RADIATIVE TRANSITIONS AND UP-CONVERSION CHARACTERISTICS OF ER3+ IONS IN SIMPLE PSEUDOTERNARY FLUORIDE GLASSES MF(N)-BAF2-YF3 (M-ZR, HF, AL, SC, GA, IN, OR ZN)

Optical properties of Er3+-doped fluoride glasses in the pseudoternary systems MF(n)-BaF2-YF3, where M is Zr, Hf, Al, Sc, Ga, In, or Zn, were investigated, and the variation of the local structure was discussed. Of the three Judd-Ofelt Omega(t) parameters (t = 2, 4, 6) that dominate the f-f transition probabilities of Er3+ ions, Omega(2) increased as the cationic field strength of network-forming M(n+) ions was increased. Omega(6) showed a correlation with the Er-F bond length. The intensity of the S-4(3/2) --> I-4(15/2) green upconversion luminescence at 0.55 mu m induced by 0.80-mu m laser pumping varied with the kind of MF(n); the InF3-based glass showed the largest intensity, and the AlF3-based glass the lowest. The quantum efficiency and nonradiative decay rates of the S-4(3/2) level changed with M(n+) and were not strongly dependent on the cutoff phonon energy of the host. The transition probability of the excitation process at 0.80-mu m absorption and that of 0.55-mu m emission can play a more important role in the upconversion intensity than the nonradiative loss in the present fluoride glasses with a low multiphonon decay rate.