NIR To Visible Upconversion In Rare-Earth Ion-Doped NaYF_4 Crystals

摘要

In this paper we investigate the infrared-to-visible upconversion luminescence in bulk crystals and nanocolloid filled photonic crystal fiber with ytterbium and erbium co-doped NaYF4 upconversion phosphor. The phosphor was prepared by using simple co-precipitation synthetic method. The initially prepared phosphor has very weak upconversion fluorescence. The fluorescence significantly increased after the phosphor was annealed at a temperature of 400°C. Nanocolloids of this phosphor were obtained using water and methanol as solvents and they were utilized as laser filling medium in photonic crystal fibers. Under 980nm laser excitation very strong upconversion signals were obtained at 408 nm, 539 nm and 655 nm. Efficiency and decay life time study of the upconverted emissions was conducted to understand the upconversion mechanisms. The reported nanocolloids are good candidates for fluorescent biosensing applications and also as a new laser filling medium in fiber lasers.