No abstract

No abstract

No abstract

Glasses of composition (x − 1)PbOؒ(100 − x)GeO 2 ؒ1Ln 2 O 3 , with x = 30 mol% (Ln = Nd, Eu, Er), 40 mol% (Ln = Pr, Nd, Sm, Eu, Dy, Ho, Er, Tm), and 50 mol% (Ln = Eu, Er), have been prepared by quenching the oxidic melts. From the optical absorption and emission spectra in the ultravioletvisible-near-infrared (UV-VIS-NIR) region, the intensity parameters, spontaneous emission probabilities, branching ratios, radiative lifetimes, and, for selected NIR transitions, peak stimulated emission cross sections have been obtained. The trends observed in the intensity parameters have been discussed, as a function of the number of f electrons as well as a function of the lead content. As the amount of lead increases, the covalency of the Ln−O bond increases, the symmetry of the rare-earth site increases, and the dopant site distribution narrows. The peak stimulated emission cross sections rank among the highest found for oxide glasses.

Zinc tellurite glasses of compositions 19ZnO-80TeO 2 -1Ln 2 O 3 with Ln= Eu, Er, Nd and Tm were prepared by melt quenching. The absorption spectra were measured and from the experimental oscillator strengths of the f f transitions the Judd-Ofelt parameters V u were obtained. The values of the V u parameters are in the range usually observed for oxide glasses. For Nd 3 + and Er 3 + , luminescence spectra in the near infrared were measured and the stimulated emission cross sections | p were evaluated for some laser transitions. The high values of | p , especially for Nd 3 + , make them possible candidates for optical applications. Fluorescence line narrowing (FLN) spectra of the Eu 3 + doped glass were measured at 20 K, and the energies of the Stark components of the 7 F 1 and 7 F 2 states were obtained. A crystal field analysis was carried out assuming a C 26 site symmetry. The behaviour of the crystal field ratios B 22 /B 20 and B 44 /B 40 agrees reasonably well with the values calculated using the geometric model proposed by Brecher and Riseberg. The crystal field strength at the Eu 3 + sites appears to be very low compared to other oxide glasses.