Near-infrared emission and upconversion in Er3+-doped TeO2-ZnO-ZnF2 glasses

► High absorption and emission cross-sections for the 4I13/2↔4I15/2 transition suitable for EDFAs. ► The increase of fluorine content leads to longer lifetimes of excited levels of Er3+ ions. ► Increase of the red upconversion emission with concentration due to ETU processes.