Investigation of upconversion luminescence in Er^3+/Yb^3+ co-doped Nb_2O_5-based glasses prepared by aerodynamic levitation method

The aerodynamic levitation method has been employed to fabricate Er3+/Yb3+ co-doped Nb2O5-La2O3-Ta2O5 glasses. The maximum phonon energy is about 735 cm−1 and the phonon density decreases with the increase of Yb3+. Small phonon density is favorable for upconversion luminescence. The absorption intensity at ~976 nm is improved by Yb3+. The glasses show high thermal stability and glass forming ability is enhanced by Yb3+. Green, red, and near infrared emissions are obtained and upconversion luminescence increases with Yb3+, which agrees well with the analysis of Raman and absorption spectra. As Yb3+ increases, the lifetime is enhanced. The results of lifetime measurement confirm the tendency of upconversion luminescence with Yb3+ ions.