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

In this work, for seven compositions of 0.1–2.0 mol% Sm ³⁺ -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 Sm ³⁺ ion in ultraviolet, visible, and infrared spectral regions. Relying on absorption and fluorescence spectra, for all Sm ³⁺: glasses, J-O (Judd-Ofelt) analysis has been conducted to compute J-O parameters Ω _λ ( λ = 2, 4, 6) from experimental oscillator strengths, and using such parameters, radiative aspects like transition probabilities, branching ratios, and radiative decay times of ⁴G _5/2 metastable state to ⁶H _11/2, ⁶H _9/2, ⁶H _7/2, and ⁶H _5/2 levels have been estimated. Ω ₂ reduced continually as Sm ₂O ₃ content increased from 0.1–2.0 mol%, hinting at improved symmetry and ionicity between Sm ³⁺ ions and related ligands. Four luminescence bands centered at 565 nm, 602 nm, 648 nm, and 710 nm ascribed to transitions from ⁴G _5/2 → ⁶H _5/2, ⁶H _7/2, ⁶H _9/2, and ⁶H _11/2 levels sequentially are obtained under intense λ _exci. = 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% Sm ³⁺ 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 Sm ³⁺ 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, ⁴G _5/2 level decay profiles exhibited single and double exponential characters at lower (0.1 and 0. 25 mol% Sm ³⁺) and higher (˃ 0.25 mol% Sm ³⁺) doping contents accordingly for deducing τ _exp (experimental decay time). Here τ _exp of ⁴G _5/2 state ( λ _exci. = 401 nm, λ _emi. = 602 nm) gradually decreased with an increase in Sm ³⁺ 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 Sm ³⁺ ion fluorescence transitions in studied glasses. In all samples, possessing lesser CR rates and higher quantum efficiency, 0.1 mol% Sm ³⁺: glass could be opted for producing effective visible lasing action upon violet excitation.