Effect of Yb3+ concentration on optical properties of Yb:CaF2 transparent ceramics

In Yb:CaF2, the coordination of Yb3+ in the CaF2 lattice determines the spectroscopic properties that make Yb:CaF2 a good candidate for high power laser applications. In this work, we measure the optical absorption, emission, and fluorescence lifetime of 0.1, 1, 5, and 10 at% Yb:CaF2 ceramics to determine whether Yb3+ substitutes as hexamer clusters giving rise to the tenability and long fluorescent lifetime observed in Yb:CaF2 single crystals. Absorption and emission spectra show that the concentration of Yb3+ present in hexamer clusters, as opposed to isolated ions, increases with increasing Yb3+ content. Fluorescence lifetime also increases with increasing Yb3+ content. Laser testing on a 1 at% Yb:CaF2 transparent ceramic demonstrates that these materials are viable laser gain media. (C) 2011 Elsevier B.V. All rights reserved.