Optical and structural characterization of rare earth doped niobium phosphate glasses

Abstract

Phosphate glasses containing up to 45mol% of niobium were obtained. X-ray diffraction, infrared, Raman, and optical absorption spectroscopy were used to analyze those materials. The refractive index varies from 1.70 to 1.85 as the amount of Nb increases. Niobium phosphate glasses with optical transparence in the (400–2500nm) range were produced. The cut off varied from 342nm to 378nm as a function of the Nb concentration. The cut off is due to the charge transfer O2→Nb5+. Glasses containing 10mol% of Nb2O5 are the most promising materials to be used as rare-earth ions hosts because they are chemically resistant, and show optical transparency in the spectral range of visible to infrared. Doping the glasses with 1–5mol% of Er, Ho, Pr, and Yb ions does not change the glass structure, as measured by X-ray diffraction, infrared, and Raman spectroscopy. The fluorescence lifetimes were determined for Nd, Yb, and Er, and the absorption cross-section were determined for all ions. The energy transfer in co-doped Yb–Er system was measured, and the lifetime of excited states and the luminescence efficiency were determined to be 91% for the Er 4I11/2 level, in the Yb–Er co-doped glasses.