Spectroscopic properties of the Er³⁺ doped Tungsten-tellurite glasses with P₂O₅

In recent years, Er³⁺ -doped glasses with a broad 1.5 μm emission band originating from ⁴I_{13/ 2}-⁴I_15/2 transition of Er³⁺ have been extensively investigated for use in erbium-doped fiber amplifiers (ED-FA). Among the reported materials, Er³⁺ -doped telluride glasses exhibited a wide 1.5 μm emission band and a large stimulated emission section and high 1.5 μm emission efficiency. However, as a host for EDFA, telluride glass has some major drawbacks. One of them is the phonon energy of the glass is about 770 cm^-1, which leads to the ⁴I_{11/ 2}-⁴I_13/2 nonradiative relaxation rate too slow to allow efficient pumping at 980 nm. To overcome this drawback, S. Shen et al. added WO₃, with vibronic energy of W-O bond of 920 cm^-1, into the glass to form tungsten-tellurite glasses. This composition modification increased the nonradiative relaxation rate of the ⁴I_11/2 transition and made improvement of population feeding efficiency of ⁴I_13/2 from the ⁴I_11/2 level pumped at 980 nm. In this paper, P₂O₅ was introduced into Er³⁺ -doped tungsten-tellurite glasses. Emission, absorption and upconversion spectra of the glasses are studied. It is observed that the nonradiative relaxation rate of ⁴I_11/2 transitions and the 1.5 μm emission efficiency increases with the increase of P₂O₅ content, while, the upconversion luminescence was suppressed. The nonradiative relaxation rate of ⁴I_{11/ 2}-⁴I_13/2 transition in a glass with 6% P₂O₅ is about 3.5 times greater than that without P₂O₅. The present results indicate that telluride glasses with P₂O₅ addition may be a promising candidate medium for broadband erbium-doped fiber amplifiers with good performance under the pumping of 980 nm.