Bright White Upconversion Emission from Tm³⁺/Yb³⁺/Er³⁺-Doped Lu₃Ga₅O₁₂ Nanocrystals

We report the synthesis of Tm 3+ /Yb 3+ /Er 3+ -doped Lu 3 Ga 5 O 12 nanocrystals prepared by a simple sol−gel method exhibiting bright white light following excitation with lower energy near-infrared light (λ exc = 980 nm) via an upconversion process. The combination of upconverted blue (from Tm 3+ ), green, and red (from Er 3+ ) emissions resulted in the white luminescence, which is intense and visible to the naked eye at a laser power less than 30 mW (3.4 W/cm 2 ). The calculated Commission internationale de l′éclairage (CIE) color coordinates, which is the standard reference for defining colors, fall well within the white region and shift only slightly with the incident laser powers indicating that the material might be promising for the development of devices such as white light lasers and LEDs.