Adjustable multicolor emission from the combination of up-conversion in Tm3+/Tb3+/Yb3+ tri-doped Na5Lu9F32 single crystals

Abstract Cubic Na5Lu9F32 fluoride single crystals tri-doped with various Tm3+/Tb3+/Yb3+ concentrations were grown by an improved Bridgman method. The absorption spectra and fluorescence spectra of Tm3+/Tb3+/Yb3+ tri-doped Na5Lu9F32 single crystal were studied systematically. The colors of up-conversion (UC) luminescence could be tuned effectively by adjusting both the doing rare earth ion concentration and the excitation laser power. The chromaticity coordinate and correlated color temperature (CCT) of the emission from the combination of the above up-conversion lights vary from (0.248, 0.261) and 18250 K to (0.325, 0.400) and 5744 K as the Tm3+/Tb3+/Yb3+ doping concentration change from 0.3 mol% Tm3+/0.3 mol% Tb3+/1 mol% Yb3+ to 0.3 mol% Tm3+/0.8 mol% Tb3+/1 mol% Yb3+ excited by a 980 nm radiation. A favorable white light emission with chromaticity coordinates of (0.297, 0.322) could be obtained from Tm3+ (0.3 mol%)/Tb3+ (0.6 mol%)/Yb3+ (1 mol%) tri-doped Na5Lu9F32 single crystal. Two-photon and three-photon absorptions dominated in the conversion processes from the infrared to visual luminescence revealed with the help of the relationship between the up-conversion emission intensity and the excitation pump power. The probable mechanism in charge of the color change of UC in Tm3+/Tb3+/Yb3+ ion doped single crystal was investigated.