Effect of concentration variation on 2.0 µm emission of Ho3+-doped SiO2–Al2O3–Na2CO3–SrF2–CaF2 oxyfluorosilicate glasses

Abstract

The concentration variation of Ho3+ ion-doped SiO2–Al2O3–Na2CO3–SrF2–CaF2 glasses has been prepared by conventional melt quenching method. The thermal stability of 1 mol % of Ho3+-doped oxyfluorosilicate glass has been calculated using the differential thermal analysis (DTA) spectra. The phenomenological Judd–Ofelt intensity parameters Ωλ (λ = 2, 4 and 6) were calculated for all concentrations of Ho3+ ions. The luminescence spectra in visible region of Ho3+ ion-doped glasses were recorded under the excitation wavelength of 452 nm. The spectra consists of several intense emission bands (5F4, 5S2) → 5I8 (547 nm), 5F3 → 5I8 (647 nm), 5F5 → 5I7 (660 nm) and (5F4, 5S2) → 5I7 (750 nm) in the range 500–780 nm. The fluorescence emission at ∼2.0 µm (5I7 → 5I8) was observed under the excitation of 488 nm Ar-ion laser. The stimulated emission cross section for 5I7 → 5I8 transition (∼2.0 µm) varies from 8.46 to 9.52 × 10−21 cm2, as calculated by the Fuchtbauer–Ladenburg (FL) theory. However, Mc-Cumber theory was used to calculate emission cross section values about 4.24–5.75 × 10−21 cm2 for the 5I7 → 5I8 transition in all concentrations of Ho3+-doped oxyfluorosilicate glasses. Therefore, these results reveal that the 0.5 mol % of Ho3+-doped oxyfluorosilicate glasses, exhibiting higher emission cross section, has potentially been used for laser applications at ∼ 2.0 µm.