Blue cooperative emission in Yb3+ - doped GeO2 - PbO glasses

Investigation of the blue cooperative luminescence in a binary composition of GeO2-PbO glasses with different Yb3+ concentrations is reported. High refractive index (1.96) and large transmission window (0.4 up to 5.0 micron) are characteristics of this vitreous system. Luminescence and lifetime measurements in the visible and near IR regions were performed to investigate the spectroscopic characteristics of the glasses. Visible emission around 507 nm was detected in all samples. The visible emission intensity increases with the Yb2O3 content at least up to 2.0 wt%, which represents the maximum Yb2O3 concentration possible for this glass system. The visible lifetimes are about half of their respective near IR ones, and the blue luminescence comes from a cooperative process. A rate equation was used to describe the behaviour of the cooperative emission intensity as a function of Yb2O3 concentration; a good agreement with the calculated and measured cooperative luminescence was achieved. 16 refs.