Energy migration and transfer of Tm3+-Gd3+-Dy3+ system in NaGdF4 under VUV and UV excitations

Based on the basis of the quantum cutting principle, the possibility to obtain two blue photons under excitation of one VUV photon in NaGdF4:Tm3+, Dy3+ has been studied using spectroscopic technique. The Gd3+→Dy3+ transfer preceded by energy migration among the Gd3+ ions is mainly governed by the exchange interaction. The quantum efficiencies for the Gd3+→Dy3+ energy transfer have an optimal value for acceptor concentration at about image and concentration quenching can be observed obviously.