Energy transfer and upconversion processes in Nd31-doped GeO2–PbO–Nb2O5 glass

The optical properties of Nd3+-doped lead germanate glass of composition (in mol. %) 60GeO2–25PbO–15Nb2O5 have been investigated for several Nd3+ concentrations at various temperatures by steady-state and time-resolved laser spectroscopy. Judd–Ofelt parameters were derived from the absorption spectrum and used to calculate the 43/2→411/2 stimulated-emission cross section and the 43/2 radiative lifetime. The spectral features of the time-resolved fluorescence line narrowing 43/2→49/2 emission spectra obtained under resonant excitation reveal the existence of spectral migration of excitation among the Nd3+ ions. Analysis of the time evolution of the 43/2→49/2 narrowed emission showed that the electronic mechanism responsible for the ion–ion interaction can be identified as a dipole–dipole energy-transfer process. Green, orange, and red emissions were observed in this glass under continuous-wave infrared laser excitation and are attributed to transitions from the 47/2 level.This research has been supported by the Spanish government (Comision Interministerial de Ciencia Tecnologia, contract MAT97-1009) and Basque Country University (contract G21/98).Peer reviewe