Upconverted nanoparticles for photonic applications

Abstract

The effects of the erbium concentration, crystal hosts and co-dopant on the up converted emission of Er³⁺ in oxide nanocrystals are reported. The effects of the Er3+ concentration and co-dopant (Yb³⁺) in the ZrO₂ matrix on the up converted emission are reported. The presence of co-dopant (Yb³⁺) also increases the overall intensity of the up converted emission. A cw diode laser at 975 nm was used as a pump source for resonant sequential excitation of the I-4(11/2) and F-4(7/2) levels. Green and red up conversion emission at 550 nm and 670 nm were observed from these oxide nanocrystals with 975 nm excitation. The overall intensity decreases with an increasing concentration of erbium in different hosts. In up conversion emission intensity for the same concentration of Er ions, BaTiO₃ host showed a highest up conversion emission intensity than that of ZrO₂ and TiO₂ host. The emission spectra and the pump intensity dependence of the luminescence intensities confirm that up converted emission in these materials is due to two-photon excited-state absorption (ESA) process.