Visible-to-near-IR luminescence at stepwise up-conversion in Yb,Ho:GGG under IR diode pumping

Powerful visible-to-near-IR luminescence is observed in a Gadolinium Gallium Garnet crystal co-activated with Yb3+ (similar to15 at%) and Ho3+ (similar to 0.1 at%) at CW laser diode excitation (lambda = 938 nm). The main visible emission band is observed in the green with its peak at lambdasimilar to540nm and measured to be about 8-10% with respect to Yb3(+) IR luminescence (lambdasimilar to1000 nm). Red (lambdasimilar to650 nm) and near-IR (lambdasimilar to755 nm) emission bands are also observed but are weaker (about 3-5%). Analysis of the crystal absorption and luminescence spectra allows one to conclude that Yb3+-Ho3+ stepwise up-conversion is the mechanism explaining the phenomenon. (C) 2002 Elsevier Science B.V. All rights reserved.