Novel rare earth doped tellurite glasses for fiber lasers in the 2-micron wavelength region

In this paper Tm-doped tellurite glasses (75TeO2-20ZnO-5 Na2O, mol%) were prepared and characterized, and codoping with Yb was investigated in order to improve pump efficiency and wavelength emission range. Emission spectra and lifetime measurements were obtained by pumping Tm-doped tellurite glasses at 800 nm and Yb-Tm co-doped tellurite glasses at 980 nm, thus exploiting the Yb-Tm energy transfer mechanism. Highly Yb-doped Tm-tellurite glasses were investigated (Yb2O3 concentrations up to 5 wt%) and an increase in 3F4 lifetime with Yb2O3 concentrations higher than 3% was observed. This showed that high amounts of Yb do not affect lifetime of the metastable state, thus allowing investigation of lasers in this range of doping concentrations.