Spectroscopic investigations of Dy3+ doped borogermanate glasses for laser and wLED applications

This work presents the optical and luminescence properties of Dy3+ ions doped gadolinium borogermanate glasses (BGGDx) prepared by conventional melt-quench method in order to investigate their potential utilization as solid state lasers and white light-emitting diodes. The XRD pattern confirms the glassy character of the material. The calculated bonding parameters suggest the ionic bonding character of Dy3+ ions with the local host. The variation of the optical band gaps which were calculated from Tauc method have been correlated with the structural changes in the glass matrix. Using the emission spectra, Judd-Ofelt analysis were performed to determine the various radiative properties for different excited states. Higher branching ratio, optical gain bandwidth and optical gain values of F-4(9)/2 -> H-6(13/2) transition point to the possible laser action of Dy3+ in gadolinium borogermanate glasses in the visible region. The experimental decay times of F-4(9/2) excited state exhibit non-exponential behavior for all concentrations and decrease with increasing Dy3+ ion content. Decay times, multipolar interactions and energy transfer parameters for excited states of Dy3+ ions in BGGDx glasses have been evaluated through Inokuti-Hirayama model. As functions of concentration and excitation wavelength the yellow to blue ratios, CIE chromaticity coordinates (x,y) and correlated color temperatures (CCT) were also evaluated from the luminescence spectra of studied glasses. For all concentrations and excitation wavelengths the (x,y) and CCT values of BGGDx glasses take part in the pure white light region.