Green, orange, and red upconversion luminescence in Nd 3+/Yb 3+: Cs 2NaGdCl 6 powders under 785 nm laser excitation

Abstract

Nd 3+:Cs 2NaGdCl 6 and Nd 3+, Yb 3+:Cs 2NaGdCl 6 polycrystalline powder samples were prepared by Morss method E. Under 785 nm semiconductor laser pumping, the upconversion luminescence of Nd 3+ ions in Cs 2NaGdCl 6 was investigated at room temperature, and three upconversion emissions near 538 nm (Green), 603 nm (Orange), and 675 nm (Red) were observed and assigned to 4G 7/2→ 4I 9/2, ( 4G 7/2→ 4I 11/2; 4G 5/2→ 4I 9/2), and ( 4G 7/2→ 4I 13/2; 4G 5/2→ 4I 11/2), respectively. The dependences of these upconverted emissions on laser power and Nd 3+ ion concentration were investigated, to explore the upconversion mechanism. The effect of doping Yb 3+ ions on the upconversion luminescence of Nd 3+ in Cs 2NaGdCl 6 was also studied under 785 nm laser excitation. The energy transfer processes were discussed as the possible mechanism for the above upconversion emissions.