Intense yellow luminescence from Dy 3+ -doped TeO 2 -WO 3 -GeO 2 glasses: structural and optical characterization.

Different concentrations of Dy3+ -doped oxyfluoride tellurite (TWGDy) glasses of composition (85  -  x) TeO2   +  5 WO3   +  10 GeO2   +  x DyF3 , where x  =  0, 0.1, 0.5, 1.0 and 2.0 mol% were prepared by melt quenching method. The Judd-Ofelt theory was applied to study the luminescence properties. Three phenomenological Judd-Ofelt (Ω λ=2,4,6 ) intensity parameters were obtained as Ω2   =  4.90  ×  10-20 cm2 , Ω4   =  1.73  ×  10-20 cm2 and Ω6   =  1.48  ×  10-20 cm2 for 0.5 mol% of Dy3+ -doped TWGDy glass. When excited at different wavelengths, the TWGDy glasses exhibit three emission bands due to 4 F9/2   →  6 H15/2 (blue), 4 F9/2   →  6 H13/2 (yellow) and 4 F9/2   →  6 H11/2 (red) transitions. The excitation wavelength was optimized as 453 nm for strong and proficient luminescence from TWGDy glasses. Beyond 0.5 mol% of Dy3+ concentration, the TWGDy glasses show luminescence quenching. The laser characteristic parameters such as effective bandwidth, stimulated emission cross-section, gain bandwidth and optical gain were determined using the emission spectra and radiative parameters. The 0.5 mol% of Dy3+ -doped TWGDy glass could be potential to design a new class of yellow laser material.