Upconversion in Nd-Tm-Yb triply doped oxyfluoride glass-ceramics containing CaF2 nanocrystals

Upconversion and energy transfer processes in Nd3+-Tm3+-Yb3+ triply doped oxyfluoride glass-ceramics containing CaF2 nanocrystals have been studied. Under 792 nm excitation, we investigated the strong blue emission from Tm3+ ions in Tm3+-Yb3+, Tm3+-Nd3+, and Nd3+-Tm3+-Yb3+ doped glass-ceramics. The Nd3+-Tm3+-Yb3+ doped glass-ceramics has shown the strongest blue emission via a multiple-step energy transfer processes following the ground state absorption of Tm3+ and Nd3+ ions. In the Nd3+-Yb3+ doped glass-ceramic, much enhanced visible emission was observed due to the back transfer from Yb3+ ions. However, under 980 nm excitation of Yb3+ ions, the triply doped glass-ceramics showed slightly weaker visible upconversion emission than the Tm3+-Yb3+ and Nd3+-Yb3+ co-doped glass-ceramics. Detailed upconversion mechanisms for observed emissions were suggested.