The optical properties of Nd<sup>3+</sup>-doped lead germanate glass of composition (in mol. %) 60GeO<sub>2</sub>–25PbO–15Nb<sub>2</sub>O<sub>5</sub> have been investigated for several Nd<sup>3+</sup> 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 <sup>4</sup>F<sub>3/2</sub>→<sup>4</sup>I<sub>11/2</sub> stimulated-emission cross section and the <sup>4</sup>F<sub>3/2</sub> radiative lifetime. The spectral features of the time-resolved fluorescence line narrowing <sup>4</sup>F<sub>3/2</sub>→<sup>4</sup>I<sub>9/2</sub> emission spectra obtained under resonant excitation reveal the existence of spectral migration of excitation among the Nd<sup>3+</sup> ions. Analysis of the time evolution of the <sup>4</sup>F<sub>3/2</sub>→<sup>4</sup>I<sub>9/2</sub> 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 <sup>4</sup>G<sub>7/2</sub> level.
© 2000 Optical Society of America
(160.5690) Materials : Rare-earth-doped materials
(190.7220) Nonlinear optics : Upconversion
(300.6360) Spectroscopy : Spectroscopy, laser
(300.6500) Spectroscopy : Spectroscopy, time-resolved
R. Balda, M. Sanz, J. Fernández, and J. M. Fdez-Navarro, "Energy transfer and upconversion processes in Nd3+-doped GeO2–PbO–Nb2O5 glass," J. Opt. Soc. Am. B 17, 1671-1677 (2000)