Comparative study of optical properties of Ho3+ -doped RE2O3-Na2O-ZnO-TeO2 glasses

Tellurite glasses of the composition xHo2O3-(7-x)RE2O3−3Na2O-25ZnO-65TeO2 were prepared by the melt quenching-technique. Absorption (300 K) and fluorescence (300 K) spectra as well as the lifetimes from excited states are presented and discussed in details. The analysis of the absorption spectrum at 300 K has been carried out for determination of phenomenological Ωλ (λ = 2, 4, 6) Judd-Ofelt parameters. Based on the Judd-Ofelt theory, the radiative transition probabilities (AT), branching ratios (βR) and radiative lifetimes (τR) of the emitting levels of Ho3+ ion have been determined. The experimental lifetime of the 5I7 level has been significantly reduced in comparison to the radiative lifetime. It was found that the quenching of emission from the 5I7 level of the Ho3+ ion is due to self-quenching process. The stimulated and effective emission cross-sections for the 5I7→5I8 transition have been calculated. The fluorescence from the 5S2 level is strongly dependent on the activator concentration. The obtained results show that among three types of glasses, Ho3+-doped Y2O3-Na2O-ZnO-TeO2 glasses are the most promising candidates for a 2 µm laser host as well as an efficient phosphor with green luminescence.