Green fluorescent Ho3+-doped TeO2 + WO3 + GeO2 + Ho2O3 glasses for lighting devices
摘要
Green fluorescence emitting TeO2 + WO3 + GeO2 + Ho2O3 glasses containing different Ho3+ doping (TWGHox) were prepared by melt quench technique. The glassy phase was examined through powder X-ray diffraction. Several spectroscopic properties were calculated from optical absorption spectral results adopting Judd–Ofelt theory. The pumping wavelength producing efficient fluorescence was selected as 454 nm. The Ho3+ doping was optimized as 0.5 mol% based on concentration-dependent emission study. Upon 454 nm pumping, TWGHox reveals two fluorescence bands positioned at 548 nm and 660 nm due to (5S2 + 5F4) → 5I8 and 5F5 → 5I8 transitions, respectively. Thermal sensitivity was examined through temperature dependence fluorescence study. The effect of Ho3+ doping on emitted color and its purity was studied. Fluorescence decay dynamics of (5S2 + 5F4) levels were studied controlling λex = 454 nm and λem = 548 nm. The fluorescence quantum efficiency was calculated from the decay time, while the fluorescence quantum yield was estimated using an integrating sphere connected to a spectrofluorimeter. The quenching in luminescence and decay time were ascribed to non-radiative cross-relaxation transitions. The applicability for green laser source was verified by calculating emission cross-sections, gain band width, figure of merit, quantum efficiency, and quantum yield.