Strong crystal-field effect and efficient phonon assisted Yb3+→Tm3+ energy transfer in a (Yb3+/Tm3+) co-doped high barium-tellurite glass

Strong ~1.83 µm NIR-emission of the Tm3+-glass and its calculated high values of gain cross-section suggest that the glass is prospective for use as 1.75-1.90 µm solid state laser medium; while the observed intense 804 nm upconversion emission of the co-doped glass indicates that the material should be useful as bio-marker.