Holmium doped bismuth-germanate glasses for green lighting applications: A spectroscopic study

Holmium (Ho3+) -doped bismuth-germanate glasses with the chemical combination of (40-x) GeO2 + 20 Bi2O3 + 20 Na2O + 10 Gd2O3 + 10 BaO + x Ho2O3 (x = 0.1, 0.5, 1.0, 1.5 and 2.5) have been prepared by melt-quenching method. These glasses were characterized for spectroscopic properties through optical absorption, photoluminescence excitation and photoluminescence emission. Judd-Ofelt (JO) intensity (Ωλ, λ = 2, 4, 6), and radiative parameters were evaluated with the help of the absorption spectra. Intense emission band was observed at a wavelength of 548 nm in the green region compared to other emission bands. Stimulated emission cross-section of GeBiNaGdBaH was found to be 0.18 × 10−20 cm2 and compared with other reported glasses. High lifetime of the 5S2+5F4 level is reported as 25 μs for the GeBiNaGdBaH15 glass. The CIE chromaticity diagram has demonstrated the strong emission for the GeBiNaGdBaH glasses in the green region at around 548 nm, and suggest that the glasses could be useful for green lighting applications.