Structural and optical properties of Dy~(3+) doped Aluminofluoroborophosphate glasses for white light applications

摘要

Dy~(3+) doped Aluminofluoroborophosphate glasses (BPAxD) have been prepared following conventional melt quenching technique and their structural and optical properties were explored through XRD, FTIR, optical absorption, excitation, emission and decay measurements. The coexistence of BO_3 groups in borate rich domain and BO_4 groups in phosphate rich domain have been confirmed through vibrational energy analysis. Negative bonding parameter (δ) values indicate that, the metal-ligand environment in the prepared glasses is of ionic in nature. The oscillator strength and the luminescent intensity Ω_λ (λ =2, 4 and 6) parameters are calculated using Judd-Ofelt theory. The radiative properties such as transition probability (A), stimulated emission cross-section (σ_P~E) and branching ratios (β) have been calculated using JO intensity parameters and compared with the reported Dy~(3+) doped glasses. Concentration effect on Y/B intensity ratios and the CIE chromaticity coordinates were calculated for the generation of white light from the luminescence spectra. The color purity and the correlated color temperature were also calculated and the results are discussed in the present work. The decay of the ~4F_(9/2) excited level is found to be single exponential for lower concentration and become non-exponential for higher concentration. The non-exponential behavior arises due to the efficient energy transfer between the Dy~(3+) ions through various non-radiative relaxation channels and the decay of the ~4F_(9/2) excited level have been analyzed with IH model. Among the prepared glasses, BPA0.5D glass exhibits higher σ_P~E, β_R, σ_P~E × σ_P~E, σ_P~E × Δλ_(eff) and η values for the ~6H_(13/2) emission band which in turn specifies its suitability for white LEDs, laser applications and optical amplifiers.