Holmium doped Lead Tungsten Tellurite glasses for green luminescent applications

Lead Tungsten Tellurite (LTT) glasses doped with different concentrations of Ho3+ ions have been synthesized using the melt quenching method and characterized to understand their visible emission characteristic features using optical absorption and photoluminescence spectral studies. The Judd-Ofelt (JO) parameters measured from the absorption spectral features were used to evaluate radiative properties such as transition probability (AR), branching ratio (βR) and radiative lifetimes (τR) for the prominent fluorescent levels of Ho3+ ions in LTT glasses. The photoluminescence spectra recorded for all the Ho3+ doped LTT glasses at an excitation wavelength 452 nm gives three prominent emission transitions 5F4→5I8, 5F5→5I8 and 5F4→5I7, of which 5F4→5I8 observed in visible green region (546 nm) is relatively more intense than the other two transitions. The intensity of 5F4→5I8 emission transition in these glasses increases up to 1 mol% of Ho3+ ions and beyond concentration quenching is observed. Branching ratios (βR) and emission cross-sections (σse) were evaluated for the intense emission transition 5F4→5I8 in these glasses to understand the luminescence efficiency in visible green region (546 nm). The CIE chromaticity coordinates were also evaluated in order to understand the suitability of these glasses for visible luminescence. From the measured emission cross-sections and CIE coordinates, it was found that 1 mol% of Ho3+ ions in LTT glasses are most suitable for visible green luminescence in principle.