Investigation of infrared emission and lifetime in Tm doped 75TeO2:20ZnO:5Na2O (mol%) glasses: effect of Ho and Yb co-doping

In this paper we describe fabrication and characterization of rare-earth-doped active tellurite glasses to be used as active laser media for fiber lasers emitting in the 2 lm region. The base composition is (mol%): 75TeO2–20ZnO–5Na2O with different concentrations of Tm3+, Yb3+ and Ho3+ as dopants or co-dopants. Optical properties of doped glasses were studied and pumping at 800 nm and at 980 nm were tested in order to compare the efficiency of two pumping mechanisms. Optical characterization carried out on glasses containing only Tm3+ ions indicated the optimum concentration of Tm2O3 in terms of emission efficiency as 1 wt%. The addition of 5 wt% of Yb2O3 to Tm3+-doped glasses led to the best results in terms of intensity of fluorescence emission and of lifetime values. Yb and Ho codoped Tm-tellurite glass was measured in emission.