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[EN]: In this work, we have investigated the existence of energy transfer among Nd3+ ions in fluoroarsenate glasses of the Na4As2O7, BaF2, YF3 system with different Nd3+ concentrations (0.5, 2, 3, 4, and 5 mol%) by using time-resolved fluorescence line narrowing spectroscopy. The spectral features of the time resolved fluorescence line narrowing 4F3/2→4I9/2 emission spectra obtained under resonant excitation reveal the existence of spectral migration of excitation among the Nd3+ ions. The analysis of the time evolution of the 4F3/2→4I9/2 narrowed emission shows that the electronic mechanism responsible for the ion–ion interaction can be identified as a dipole–dipole energy transfer process., [FR]: Le transfert d’énergie entre ions Nd3+ a été étudié dans des verres de fluoroarséniates à différentes concentrations en néodyme par spectroscopie de fluorescence à résolution temporelle en rétrécissement de bande. Les résultats mettent en évidence la migration spectrale de l’excitation des ions Nd3+. Le mécanisme responsable de lˈinteraction ion–ion a été identifié comme un processus de transfert d’énergie dipôle–dipôle., This work has been supported by the Basque Country University (Ref.: UPV13525/2001), the Basque Country Government (Ref.: PI1999-95), and the Spanish Government (Ref.: BFM2000-0352).

In this work we have studied the infrared to visible upconversion luminescence of Nd3+-doped fluoroarsenate glasses with different neodymium concentrations (0.1, 0.5, 2, 3, 4, and 5 mol%) under continuous wave and pulsed laser excitation. Green, orange, and red emissions are observed with excitation at 802 and 874 nm within the 4F5/2 and 4F3/2 levels. In addition, a weak blue emission appears under continuous wave (cw) laser excitation which under pulsed laser excitation only occurs for the most concentrated sample at 77 K. The green, orange, and red emissions can be attributed to transitions from the 4G7/2 excited state. The pump power dependencies of these upconverted emissions together with the shape of the upconverted excitation spectra which are similar to the one-photon absorption spectrum and the temporal behavior of the decays, indicate that an ETU process seems to be responsible for the observed visible luminescence, though other possible mechanisms cannot be disregarded., This work was supported by the Basque Country University (G21/98), Spanish Government CICYT Ref. MAT97-1009, and French-Spanish PICASSO program HF99-43.

International audience; Solid state NMR is a matchless tool to probe amorphous material. It provides direct information on the local and the medium range orderin complex networks. Unfortunately, chalcogenide glasses do not contain nuclei which are easily probed by NMR due to their low concentration,low sensitivity, large quadrupole moments and/or long relaxation times. Nevertheless, throughout the last decade, increasingly sophisticated NMRsequences have been implemented enabling a better understanding of the structure of these exciting materials. In this chapter, an overview ispresented of the NMR results obtained on chalcogenide glasses. Most of them were obtained from 77Se spectroscopy, but results based on 125Te, 75As,73 Ge and 71Ga are also reported.