White-Light Whispering-Gallery-Mode Lasing from Lanthanide-Doped Upconversion NaYF₄ Hexagonal Microrods

We demonstrate simultaneous red, green, and blue emission from a Yb 3+ –Er 3+ –Tm 3+ tridoped hexagonal β-NaYF 4 microrod, which supports whispering-gallery-mode (WGM) resonance, to realize white-light lasing under near-infrared excitation at room temperature. This can be done by optimizing the upconversion efficiency and emission intensity balance of the blue, green, and red peaks through the proper tuning of sensitizer (Yb 3+ ) and activator (Er 3+, Tm 3+ ) concentration in the host matrix. In addition, we minimize the difference of lasing threshold and maintain stable single-mode operation to achieve simultaneous red, green, and blue lasing by optimizing the radius of the hexagonal microrods.