Infrared-to-Visible Up-conversion in Er-Pr-Yb Triply Doped Oxyfluoride Glass Ceramics

Abstract

We synthesized Er3+-Yb3+, Pr3+-Yb3+, and Er3+-Pr3+-Yb3+-doped oxyfluoride glass ceramics containing CaF2 nanocrystals by proper thermal treatments. Spectral characteristics of down- and up-converted emissions in three kinds of glass ceramics under 365-nm and 980-nm excitations were compared and explained by cross relaxations, excited-state absorptions, and energy-transfer processes between different ions. The huge reduction of up-conversion emission in the triply doped glass ceramics under 980-nm excitation compared to the Er3+-Yb3+ codoped one was explained by the split pump power and the direct energy transfer from Er3+ to Pr3+ ions. Increasing Yb3+ concentration from 2% to 10% in the triply doped glass ceramics showed more than quadratic enhancement of the absorbed power, and we explained it by the enhanced energy-transfer efficiency from Yb3+ to Er3+ ions. We also observed enhanced up-converted emissions of Er3+ and Pr3+ ions in three kinds of glass ceramics under simultaneous excitation at 980 nm and 1550 nm, and suggested detailed up-conversion mechanisms.