Figure 7
From: Morphology evolution and pure red upconversion mechanism of β-NaLuF4 crystals
(a) Power dependence of R/G ratio for β-NaLuF4:20% Yb/1% Tm/20% Er, and (b) Er3+ concentration dependence of NIR/G ratio for β-NaLuF4:20% Yb/1% Tm/xEr under 980 nm excitation. NIR emission corresponds to the 4I13/2 → 4I15/2 transition of Er3+.
