Spectroscopic properties of Er3+-doped fluorotellurite glasses modified by Nb2O5 and WO3

We have investigated the spectroscopic properties of Er³⁺-doped fluorotellurite glasses with the basic molar composition 75%TeO₂–10%P₂O₅–10%ZnO–5%PbF₂, modified by replacing 5% TeO₂ by a metal oxide, namely WO₃ or Nb₂O₅. The absorption edge of the glasses studied has been described within the Urbach approach, while the absorption and photoluminescence spectra have been analyzed in terms of the standard Judd–Ofelt theory, along with the photoluminescence decay of the ⁴I_13/2 and ⁴S_3/2 levels of the Er³⁺ ion. The absorption and emission spectra of the ⁴I_15/2↔ ⁴I_13/2infrared transition have been analyzed within the McCumber theory to yield the peak emission cross-section and figure of merit for the amplifier gain. It appears that the fluorotellurite glass containing WO₃ as a modifier is characterized by the largest figure of merit, indicating this matrix as a promising new host for doping with Er³⁺ ions.