Spectroscopic properties and energy transfers in Tb3 +/Ho3 +/Yb3 + tri-doped oxyfluoride silicate glasses

Upon excitation with a 980   nm laser diode (LD), the upconversion luminescence (UCL) properties of Tb 3   + /Ho 3   + /Yb 3   + tri-doped oxyfluoride silicate glasses were investigated. Five distinct emissions peaked at 489, 543, 584, 623 and 662   nm are simultaneously observed and are assigned to the electronic transitions of Tb 3   + : 5 D 4 → 7 F J (J   =   6, 5, 4 and 3) and Ho 3   + : 5 F 5 → 5 I 8 , respectively. The effects of Tb 3   + and Yb 3   + concentrations on the emissions were studied. The log–log plots of the UCL intensity versus laser power show abnormal relations: the slopes are larger than those in previous reports, which could be attributed to the effect of intrinsic optical bistability (IOB) of Yb 3   + ions. In addition, the UC mechanisms were discussed in this work.