Exploration of concentration-reliant optical and luminescence aspects of Sm3+: B2O3-Gd2O3-Li2O-Na2O-LiF glasses for color displays and visible lasers utilization

Abstract

In this work, for seven compositions of 0.1–2.0 mol% Sm3+-doped transparent borate-rich glasses (prepared utilizing a quick and facile melt-quenching process), optical and visible fluorescence traits combined with luminescence decay patterns have been inspected and analyzed thoroughly. By X-ray diffraction, the amorphous phase has been clarified. Absorption spectra displayed distinctive peaks of Sm3+ ion in ultraviolet, visible, and infrared spectral regions. Relying on absorption and fluorescence spectra, for all Sm3+: glasses, J-O (Judd-Ofelt) analysis has been conducted to compute J-O parameters Ωλ (λ = 2, 4, 6) from experimental oscillator strengths, and using such parameters, radiative aspects like transition probabilities, branching ratios, and radiative decay times of 4G5/2 metastable state to 6H11/2, 6H9/2, 6H7/2, and 6H5/2 levels have been estimated. Ω2 reduced continually as Sm2O3 content increased from 0.1–2.0 mol%, hinting at improved symmetry and ionicity between Sm3+ ions and related ligands. Four luminescence bands centered at 565 nm, 602 nm, 648 nm, and 710 nm ascribed to transitions from 4G5/2 →6H5/2, 6H7/2, 6H9/2, and 6H11/2 levels sequentially are obtained under intense λexci. = 401 nm. In all emission peaks, the reddish-orange one (602 nm) is identified to be very intense in all glasses. All fluorescence bands’ intensity increased up to 0.5 mol% Sm3+ doping level and above 0.5 mol% doping content, intensity reduced regularly owing to the concentration quenching effect caused by the ET (energy transfer) via CR (cross-relaxation) channels among Sm3+ ions. CIE (Commission Internationale de l′éclairage) coordinates, CCT (correlated color temperature), dominant wavelength, and color purity have been derived from emission spectra of all investigated samples, and derived CIE (x, y) and CCT values are located in the CIE plot’s reddish-orange light region, signifying such glasses potential for color displays and orange light-emitting diodes. As CCT< 3200 K, all samples could be categorized as “warm” light sources. Further, 4G5/2 level decay profiles exhibited single and double exponential characters at lower (0.1 and 0. 25 mol% Sm3+) and higher (˃ 0.25 mol% Sm3+) doping contents accordingly for deducing τexp (experimental decay time). Here τexp of 4G5/2 state (λexci. = 401 nm, λemi. = 602 nm) gradually decreased with an increase in Sm3+ content from 0.1 m to 2.0 mol%. Non-exponential decay curves are well fitted to the Inokuti–Hirayama model for S = 6, implying that the ET process is of dipole-dipole nature for Sm-Sm ions. Later, effective bandwidth, stimulated emission cross-section, gain bandwidth, and optical gain have been calculated for all Sm3+ ion fluorescence transitions in studied glasses. In all samples, possessing lesser CR rates and higher quantum efficiency, 0.1 mol% Sm3+: glass could be opted for producing effective visible lasing action upon violet excitation.