Upconversion luminescence of Sm2+ ions

Herein, we report the phenomenon of upconversion luminescence from Sm2+ ions, which demonstrates that changeable valence lanthanides can serve as ions for optical frequency transformation. Upon excitation with a 980 nm diode laser, the doped Sm2+ ions in the hybrid material BaFCl0.5Br0.5: 1% Sm2+CaF2: 1% Yb3+ emit red upconversion fluorescence peaks at 631 nm, 644 nm, 665 nm, 689 nm, 704 nm, and 729 nm from the D-5(0,1) -> F-7(0,1,2) transitions. By transient dynamic analysis, we attributed the excitation of Sm2+ ions to the cooperation energy transfer process, in which two excited Yb3+ ions simultaneously transfer their energy to one Sm2+ ion.