Abstract
We found enhanced upconverted fluorescence in Nd3+-doped fluorozirconate glasses which were additionally doped with chlorine ions. Upon annealing between 240 and 290°C, hexagonal phase BaCl2 nanocrystals between 20 and 180 nm in diameter were formed in the glass. During the thermal processing, some of the Nd3+ ions enter the nanocrystals leading to additional splitting of the infrared fluorescence spectra and to increased upconverted fluorescence intensities. The optimum value was found for the 270°C sample where the upconverted fluorescence intensity is approximately a factor of 60 stronger than the one found for the as-made glass.