Upconversion properties of a transparent Er3+-Yb3+ co-doped LaF3-SiO2 glass-ceramics prepared by sol-gel method

Transparent 0.1ErF(3)-0-1YbF(3)-5LaF3-94.8SiO(2) (mol%) glass-ceramics was prepared by sol-gel method. Efficient upconversion emissions at 379, 407, 450, 490, 520, 540 and 660 nm were observed under 973 nm excitation. The signal at 379 nm is only similar to4.5 times weaker than the signal at 520 nm, that is readily visible by the naked eyes even with a pump power of similar to27 mW, indicating that this sample is a very good infrared-to-ultraviolet upconverter. The data obtained from transmission electron microscopy and X-ray diffraction studies indicate that the rare-earth ions were partitioned in the low phonon energy LaF3 nanocrystals embedded in silica glass. The analysis of the dynamics of the upconversion emissions from level S-4(3/2) (similar to540 nm) and level F-4(9/2) (similar to660 nm) of Er3+ suggest that distinct energy transfer excitation pathways are responsible for populating these luminescent levels. (C) 2003 Elsevier Science B.V. All rights reserved.