Dependence of cooperative luminescence intensity onYb3+spatial distribution in crystals and glasses

Abstract

Cooperative emission has been recorded in several ${\mathrm{Yb}}^{3+}$ stoichiometric crystals. Its intensity, normalized by the square of the ${}^{2}{F}_{5/2}$ excited level population, is shown to depend only on the ${\mathrm{Yb}}^{3+}$ ions spatial distribution. In most cases, other material dependent parameters do not need to be taken into account, as confirmed by a theoretical analysis. Cooperative luminescence (CL) is therefore an easy way to probe ${\mathrm{Yb}}^{3+}$ clustering in crystals and glasses. This measurement has been carried out in aluminosilicate and phosphate glasses for which CL intensity strongly varies with the glass composition. Two models of Yb distribution are proposed to relate CL and glass structure or to allow easy comparison between samples. Finally, the extension of these results to other rare-earth ions and energy transfer processes is examined. It is found that dipole-dipole energy transfer and CL interaction coefficients vary in the same way but with reduced amplitude for the former. This results from the CL dependence on a quadrupole-dipole process at short distances.