Spectroscopic studies of single near ultraviolet pumped Tb3+ doped Lithium Lead Alumino Borate glasses for green lasers and tricolour w-LEDs

Terbium ions (Tb3+) doped Lithium Lead Alumino Borate (LiPbAlB) glasses with the chemical composition 10Li2O - 10PbO - (10-x) Al2O3 - 70B2O3 - xTb2O3 (where x = 0.5, 1.0, 1.5, 2.0 and 2.5 in mol%) were synthesized via melt quench method and characterized by absorption, photoluminescence (PL) and PL decay spectral measurements. The Judd-Ofelt (J-O) intensity parameters evaluated from the oscillator strength values are further used to evaluate the radiative parameters for the prominent fluorescent levels (5D4→7Fj) of Tb3+ ions. The intensity of all the emission bands increases up to 2 mol% of Tb3+ and beyond concentration quenching took place. The decay profiles of 5D4 show single exponential for lower concentration and non-exponential for higher concentration resulting decrease in experimental lifetime (τexp) with increase in rare earth ion concentration. Such decrease in τexp and decay conversion from single to non-exponential has been attributed to the cross-relaxation processes and subsequent concentration quenching observed. The Inokuti-Hiryama (I-H) model applied to the decay spectral profiles confirms the energy transfer process between Tb3+-Tb3+ ions as dipole-dipole in nature. Higher values of stimulated emission cross-section, quantum efficiency, gain bandwidth and optical gain obtained for 5D4→7F5 transition of LiPbAlB glass with 2 mol% of Tb3+ ions suggests its suitability for green lasers. The CIE-chromaticity co-ordinates, color purity (CP) and correlated color temperature (CCT) confirms the suitability of these glasses in tricolor w-LEDs.