Role of modifier oxide in emission spectra and kinetics of Er–Ho codoped Na2SO4–MO–P2O5 glasses

The glasses of the composition 19Na2SO4–20MO–60P2O5: 1.0Ho2O3/1.0Er2O3 (M = Mg, Ca, and Ba) have been synthesized. Optical absorption and fluorescence spectra (in the spectral range 350–2100 nm were studied at ambient temperature. The spectra were characterized using Judd–Ofelt theory. From the luminescence spectra, various radiative properties like transition probability A, branching ratio β and the radiative life time τ for blue (B), green (G) and red (R) emission levels of these glasses have been evaluated. The energy transfer between the two rare earth ions (Ho3+ and Er3+) in co-doped Na2SO4–MO–P2O5 glass systems in the visible and NIR regions has also been investigated. Highest intensity, the highest quantum efficiency and maximum energy transfer with low phonon losses of B, G, and R lines has been observed in BaO mixed glasses. The reasons for such higher values of these parameters have been discussed in the light of varying field strengths at the rare earths ion site due to replacement of one modifier oxide with the other. The enhanced intensity of NIR emission (at 2.0 μm) has also been discussed in terms of cross relaxation of Er3+ ions from 4I13/2 level to 5I7 of Ho3+ ions.

The optical absorption, photoluminescence of Ho3+, Er3+ and co-doped Na2SO4–MO–P2O5 glasses mixed with three modifier oxides viz., MgO, CaO and BaO have been studied. The quantitative analysis of these results has indicated the maximum energy transfer between two rare earth ions in BaO mixed glasses Energy level diagram containing important transitions of Ho3+ and Er3+ ions and energy transfer in Na2SO4−BaO−P2O5 glasses.Figure optionsDownload as PowerPoint slideHighlights
► PL spectra of Ho3+, Er3+ ions in Na2SO4–MO–P2O5 glass system are studied.
► Role of modifier oxides (MgO, CaO, and BaO) on the emission features is investigated.
► The NIR emission ∼2.0 μm is found to be strengthened due to co-doping.
► Emission efficiency for R, B, G lines is highest for BaO mixed glasses.