Abstract
Optical properties of upconversion nanoparticles Y2O3:Er,Yb were investigated. The upconversion nanoparticles were prepared by laser ablation in liquid, which was one of the promising plasma processes to fabricate nanoparticle-dispersed solution. Highly crystalline nanoparticles with particle size of 11±3 nm were observed by electron microscope. Upconversion spectra with an excitation of 980 nm were measured by fluorescence spectrophotometer. Photon-avalanche effect of the nanoparticles, which significantly increased upconversion intensity, was observed. This phenomenon would be due to the increase in population at red emission by cross-relaxation. The ratio of red emission to green one was increased by the increase in the concentration of Yb in phosphor and the decrease in the excitation power.
