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

• Tb3 +/Ho3 +/Yb3 + doped SiO2·Al2O3·BaF2·Na2O glasses were synthesized.
• There is an ET process from Ho3 +: 5F4 to Tb3 +: 5D4 in the studied systems.
• The abnormal UC luminescence is observed at room temperature.
• The reason of abnormal phenomena lies in the intrinsic optical bistability of Yb3 +.

Upon excitation with a 980 nm laser diode (LD), the upconversion luminescence (UCL) properties of Tb3 +/Ho3 +/Yb3 + 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 Tb3 +: 5D4→7FJ (J = 6, 5, 4 and 3) and Ho3 +: 5F5→5I8, respectively. The effects of Tb3 + and Yb3 + 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 Yb3 + ions. In addition, the UC mechanisms were discussed in this work.