Concentration dependence of energy transfer from Bi³⁺ to Nd³⁺ in germanate glass

Energy transfer probabilities and efficiencies from Bi³⁺ to Nd³⁺ were calculated from the decrease of intensities and lifetimes of Bi³⁺ as a function of concentration of Nd³⁺ and from the increase of Nd³⁺ luminescence as a function of Nd³⁺ concentration. The energy transfer rate obtained by the two methods is (3.7 ± 0.2) × 10⁶ sec ^-1 M ^-1. Energy transfer was also measured versus concentration of Bi³⁺ ions by using lifetime measurements, and it was found that the transfer efficiency is maximum at 0.3 wt.% Bi³⁺ in the measured concentration range of Nd³⁺ from 0.5-1.5 wt.%. The contribution of the radiative transfer was established from the dip in the emission spectrum of Bi³⁺. It is suggested that the sensitization of Nd³⁺ luminescence by Bi³⁺ may increase the pumping range of the Nd³⁺ glass laser for mini lasers.