Optical spectroscopy of lanthanide ions in ZnO–TeO 2 glasses

Abstract

Zinc tellurite glasses of compositions 19ZnO–80TeO 2–1Ln 2O 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 Ω λ were obtained. The values of the Ω λ 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 σ p were evaluated for some laser transitions. The high values of σ 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 7F 1 and 7F 2 states were obtained. A crystal field analysis was carried out assuming a C 2 v 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.