Pr3+ ions doped single alkali and mixed alkali fluoro tungsten tellurite glasses for visible red luminescent devices

Abstract

The present work illustrates the optical absorption and fluorescence properties of Pr3+ ions doped single alkali and mixed alkali fluoro tungsten tellurite glasses prepared by using melt quenching technique. The prepared glasses were characterized by using absorption, excitation and photoluminescence (PL) spectral measurements. The energies of the absorption spectral features called oscillator strengths were calculated using area method and in turn used to evaluate the Judd-Ofelt (J-O) intensity parameters (Ω2, Ω4, Ω6). Such J-O parameters are used to estimate various radiative parameters such as radiative transition probabilities (AR), branching ratios (βR), and radiative lifetimes (τR) for the prominent fluorescent levels of Pr3+ ions in these glasses. The PL spectra of the as prepared glasses show three prominent peaks at wavelengths 488, 646 and 670 nm related to the transitions 3P0 → 3H4, 3P0 → 3F2 and 1D2 → 3H5 respectively for which emission cross-sections and branching ratios were evaluated. The variations in the spectral parameters with the variation of glass matrix composition have been examined in detailed. The decay profiles of the prepared glasses have been recorded to evaluate quantum efficiency of present series of glasses. From the measured branching ratios, emission cross-sections and quantum efficiency, it was concluded that the tungsten tellurite glasses added with potassium fluoride and doped with 1 mol% of Pr3+ions (TeWK glass) are quite suitable to produce visible red emission at 670 nm suitable to fabricate red luminescent devices.