Effect of Tm3+ codoping on the near-infrared and upconversion emissions of Er3+ in TeO2-ZnO-ZnF2 glasses

In this work, we report the near-infrared emission and upconversion of Er3+-Tm3+ codoped fluorotellurite TeO2-ZnO-ZnF2 glasses for different Tm3+ concentrations by using steady-state and time-resolved spectroscopy. A broad emission from 1350 to 1700 nm corresponding to the 3H4→3F4 (Tm3+) and 4I13/2→4I15/2 (Er3+) emissions which cover the complete telecommunication window of the wavelength-division-multiplexing transmission systems is observed. The full width at half-maximum of this broadband increases with increasing Tm3+/Er3+ concentration ratio up to a value of~150 nm. Energy transfer between Er3+ and Tm3+ ions is also observed and analyzed by both the temporal behavior of the near-infrared luminescence and the effect of Tm3+ codoping on the visible upconversion of Er3+ ions. The addition of Tm3+ reduces the upconverted green emission due to Er3+→Tm3+ energy transfer whereas the red emission is enhanced due to the cross-relaxation 3F4→3H6(Tm3+):4I11/2→4F9/2(Er3+) process.