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

Abstract Tellurite glasses of the composition xHo 2 O 3 -(7-x)RE 2 O 3 −3Na 2 O-25ZnO-65TeO 2 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 Ω λ (λ = 2, 4, 6) Judd-Ofelt parameters. Based on the Judd-Ofelt theory, the radiative transition probabilities ( A T ), branching ratios ( β R ) and radiative lifetimes ( τ R ) of the emitting levels of Ho 3+ ion have been determined. The experimental lifetime of the 5 I 7 level has been significantly reduced in comparison to the radiative lifetime. It was found that the quenching of emission from the 5 I 7 level of the Ho 3+ ion is due to self-quenching process. The stimulated and effective emission cross-sections for the 5 I 7 → 5 I 8 transition have been calculated. The fluorescence from the 5 S 2 level is strongly dependent on the activator concentration. The obtained results show that among three types of glasses, Ho 3+ -doped Y 2 O 3 -Na 2 O-ZnO-TeO 2 glasses are the most promising candidates for a 2 µm laser host as well as an efficient phosphor with green luminescence.