Spectroscopic properties and crystal-field effects in Er3+-doped tellurite and phosphate glass-ceramics

Abstract

A series of Er3+-doped 40NaPO3–40KH2PO4-10ZnCl2-10Al2O3 (Er:NKZACl, 2Er:NKZACl) and 65TeO2-20ZnO-10BaO-3La2O3 (Er:TZBO) glasses were prepared by conventional melt quenching method, in order to compare and select the best chemical composition of glasses which exhibit opimal spectroscopic properties for broadband 1.54 µm laser emission and optical amplification. The samples were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), electron probe microanalysis with wavelength dispersion spectroscopy (EPMA/WDS), energy dispersive spectroscopy (EDS) and optical spectroscopy. Judd-Ofelt analysis was performed from the absorption spectra. The line strengths (Sexp and Scal) of different transitions between the 4I15/2 ground state and 11 excited states, as well as the Judd-Ofelt intensity parameters (Ω2,Ω4,Ω6) were calculated and compared to those of other glasses. Using these parameters, transition probabilities A, branching ratios β, radiative lifetimes τrad were determined. The experimental crystal-field energy sublevels of Er3+ cations were identified from the emission spectra at 77 K and the corresponding crystal-field parameters were refined for the 1Er:NKZACl and 2Er:TZBO glasses, by means of a crystal-field Hamiltonian endowed with C2 symmetry. In our study, the composition TZBO:Er3+ (2 mol%) exhibits optimal values of 4I15/2multiplet crystal-field splitting (383.7 cm−1), high Er3+ emission cross section at 1.54 µm (σem≃7.80 ×10−21 cm2), average experimental lifetime (2.97 ms) and high quantum efficiency (η≃85.6%) of the 4I13/2→4I15/2 emission. The obtained results make this glass a promising candidate for laser application and optical amplification in the infrared spectral range.