Search Results (22)

The Judd–Ofelt (J–O) intensity parameters and oscillator strengths are key to understanding the optical transition properties of rare-earth-doped glasses. However, the scarcity of experimental samples and the complex nonlinear relationship between composition and spectral properties pose significant challenges to accurate predictions. To address this, we propose a generalizable framework that integrates conditional generative adversarial network (cGAN)-based data augmentation with an attention-embedded artificial neural network (ANN)–support vector regression (SVR) hybrid model. The cGAN generates physically plausible virtual samples to enrich data distribution and enhance generalization in sparse compositional regions. The attention mechanism in the ANN identifies critical compositional features, which are then leveraged by SVR for robust regression of parameter trends. The framework demonstrates high predictive accuracy for Er³⁺-doped glasses, achieving R² values above 0.93 for Ω₂, Ω₄, and Ω₆, and exhibits strong generalization performance on independent Dy³⁺- and Nd³⁺-doped datasets without task-specific retraining, confirming its practical applicability across multiple rare-earth ions. The model maintains consistency across diverse glass host systems (tellurite, borate, phosphate, silicate/germanate, heavy-metal oxide), and the attention analysis reveals feature importance aligned with established glass chemistry principles. Demonstrated on Er³⁺, Dy³⁺, and Nd³⁺, with potential for a broader range of rare-earth ions through transfer learning and future dataset extensions, this approach offers a data-driven, physics-informed tool for the targeted design of rare-earth optical materials in next-generation optical sensors. Full article

Lead borophosphate zinc barium glass systems doped with different concentrations of Dy₂O₃ (0.5–2.0 mol%) were fabricated using the traditional melt-quenching method. The non-crystalline nature of the synthesized glass samples was verified through X-ray diffraction (XRD) analysis, which exhibited the characteristic absence of sharp diffraction peaks. Morphological, structural, and vibrational properties were analyzed using scanning electron microscopy (SEM) and Fourier infrared transmission (FTIR) spectroscopy. Optical absorption, emission, and decay lifetime observations were recorded to evaluate the luminescence behavior of Dy³⁺ ions. Judd–Ofelt parameters (Ω₂, Ω₄, and Ω₆) were evaluated from the optical absorption spectra of all the prepared glass samples. The emission spectra revealed three dominant transitions in the visible region corresponding to the ⁴F_9/2 ⟶ ⁶H_15/2 (blue ~ 484 nm), ⁴F_9/2 ⟶ ⁶H_13/2 (yellow ~ 574 nm), and ⁴F_9/2 ⟶ ⁶H_11/2 (~663 nm) transitions. Radiative characteristics, including radiative transition probability (A_R), radiative lifetime (τ_R), and branching ratio (β_R), were calculated from the emission spectra. Among the investigated compositions, the host glass embedded with 1.0 mol% Dy₂O₃ demonstrated the maximum emission intensity was observed along with superior quantum efficiency (η = 91.68%). The chromaticity coordinates for this composition (x = 0.33, y = 0.41) are positioned close to the white-light region in the CIE 1931 chromaticity diagram. These findings suggest that incorporating 1.0 mol% of Dy₂O₃ yields the highest luminescence efficiency, making the present glass system a promising candidate for white-light-emitting and photonic device applications. Full article

Tb³⁺-doped CaF₂ single crystals are attractive materials for green photonic applications due to their low phonon energy, high optical transparency, and efficient Tb³⁺ emission. In this work, CaF₂ single crystals doped with different TbF₃ concentrations (1, 5, and 10 mol%) were grown and systematically investigated in order to clarify the concentration-dependent spectroscopic behavior of Tb³⁺ ions in a fluorite host. Optical absorption spectroscopy, Judd–Ofelt analysis, steady-state and time-resolved photoluminescence, colorimetric evaluation, and emission cross-section and gain calculations were employed. Judd–Ofelt intensity parameters typical of fluoride hosts were obtained, enabling the calculation of radiative transition probabilities and lifetimes. The emission spectra are dominated by intense green luminescence from the ⁵D₄ → ⁷F₅ transition, while the absence of ⁵D₃ emission is attributed to efficient cross-relaxation processes. Fluorescence lifetimes in the millisecond range show slight changes with Tb³⁺ concentration. Quantum efficiency increases from low to intermediate concentrations and tends to saturate at higher doping levels. CIE 1931 chromaticity coordinates confirm stable green emission, while emission cross-sections and gain parameters reveal a highest value for orange emission of 10 mol% TbF₃-doped CaF₂ crystal. These results indicate that CaF₂:Tb³⁺ single crystals are promising materials for photonic applications. Full article

In this work, Sm³⁺-activated lead phosphate glass has been studied using spectroscopic methods. Based on absorption spectrum measurements, the oscillator strengths for Sm³⁺ ions were determined and compared to those calculated from the Judd–Ofelt theory. This procedure was applied to evaluate some radiative parameters (radiative transition rates, emission branching ratios, radiative lifetime) of Sm³⁺ ions in lead phosphate glass. Further luminescent studies indicate that lead phosphate glass doped with Sm³⁺ emits intense reddish-orange light due to ⁴G_5/2 ⟶ ⁶H_7/2 transition, for which several important spectroscopic parameters like emission linewidth and lifetime, quantum efficiency, peak stimulated emission cross-section, and figure of merit for laser gain were determined. The factors for Sm³⁺ ions in lead phosphate glass are as follows: η = 53%, FWHM = 10.5 nm, τ_exp = 1.925 ms, σ_em = 7.6 × 10⁻²² cm², σ_em × τ_exp = 14.6 × 10⁻²⁵ cm²s. The experimental and theoretical results suggest that samarium-doped lead phosphate glass can be successfully used as a reddish-orange-emitting component in photonic devices. Full article

This work shows that inverse Judd–Ofelt (JO) analysis of relative absorption spectra, anchored by a single lifetime, provides JO parameters and radiative rates without absolute calibration. The method is applied to Er³⁺, Dy³⁺, and Sm³⁺ in a compositionally identical oxyfluoride glass. Three well-resolved ground-state 4f–4f absorption bands were selected. After baseline removal and wavenumber-domain integration, their normalized strengths S_rel,k (k = 1, 2, 3; k∈S) define a 3 × 3 system solved by non-negative least squares to obtain the anchor-independent ordering (Ω₂:Ω₄:Ω₆). Absolute scaling uses a single lifetime anchor. We report lifetime-scaled Ω_t and A_rad, and the normalized fractions p_k within the selected triplets; as imposed by the method, the anchor-independent ordering (Ω₂:Ω₄:Ω₆) is analyzed, while absolute A_rad and Ω_t scale with τ_ref. The extracted parameters fall within the expected ranges for oxyfluoride hosts and reveal clear ion-specific trends: Ω₂ follows Dy³⁺ > Er³⁺ > Sm³⁺ (site asymmetry/hypersensitive response), while the ordering Ω₄ > Ω₆ holds across all ions (oxide-rich networks). Er³⁺ exhibits the largest Ω₄ and the smallest Ω₆, indicative of pronounced medium-range “rigidity” with suppressed long-range polarizability; Sm³⁺ shows the lowest Ω₂ (more symmetric/less covalent coordination); and Dy³⁺ the highest Ω₂ (strong hypersensitive behavior). Uncertainty was quantified by Monte Carlo resampling of the preprocessing steps, yielding compact 95% confidence intervals; the resulting JO-parameter trends (Ω₂, Ω₄, Ω₆) and normalized f_k fractions reproduce the characteristic spectroscopic behavior known for each ion. This method enables quantitative JO outputs from uncalibrated spectra, allowing direct spectroscopic comparisons and quick screening when only relative absorption data are available. Full article

A BaF₂ single crystal co-doped with Er³⁺ and Yb³⁺ was grown by the vertical Bridgman technique and investigated for its optical and dielectric properties. Judd–Ofelt analysis yielded intensity parameters Ω₂ = 0.59, Ω₄ = 0.38, and Ω₆ = 0.27 (×10⁻²⁰ cm²), with a quality factor χ = 1.41, indicating strong radiative transitions. Under UV and near-UV excitation, emissions at 321, 405, 518, and 536 nm were observed, with radiative lifetimes ranging from 1.1 to 3.4 ms. A single dielectric relaxation process was identified, with activation energy of 0.58 eV and associated with trigonal NNN dipoles. The NNN dipole concentration was estimated at ~2.5 × 10¹⁸ cm⁻³. These results support the suitability of Er³⁺,Yb³⁺ co-doped BaF₂ crystals for luminescent and dielectric applications in advanced photonic materials. Full article

Detailed analysis covered the optical and structural properties of Eu³⁺-doped NaY₉Si₆O₂₆ oxyapatite phosphors, which were obtained via hydrothermal synthesis. X-ray diffraction patterns of NaY₉Si₆O₂₆:xEu³⁺ (x = 0, 1, 5, 7, 10 mol% Eu³⁺) samples proved a single-phase hexagonal structure (P63/m (176) space group). Differential thermal analysis showed an exothermic peak at 995 °C attributed to the amorphous to crystalline transformation of NaY₉Si₆O₂₆. Electron microscopy showed agglomerates composed of round-shaped nanoparticles ~53 nm in size. Room temperature photoluminescent emission spectra consisted of emission bands in the visible spectral region corresponding to ⁵D₀ → ⁷F_J (J = 0, 1, 2, 3, 4) f-f transitions of Eu³⁺. Lifetime measurements showed that the Eu³⁺ concentration had no substantial effect on the rather long ⁵D₀-level lifetime. The Eu³⁺ energy levels in the structure were determined using room-temperature excitation/emission spectra. Using the ⁷F₁ manifold, the Nv-crystal field strength parameter was calculated to be 1442.65 cm⁻¹. Structural, electronic, and optical properties were calculated to determine the band gap value, density of states, and index of refraction. The calculated direct band gap value was 4.665 eV (local density approximation) and 3.765 eV (general gradient approximation). Finally, the complete Judd–Ofelt analysis performed on all samples confirmed the experimental findings. Full article

In this study, we report the growth and comprehensive spectroscopic analysis of TmF₃-doped CaF₂ crystals, grown using the vertical Bridgman method. The optical absorption and photoluminescence properties of both trivalent (Tm³⁺) and divalent (Tm²⁺) thulium ions were investigated. Optical absorption spectra in the UV-VIS-NIR range reveal characteristic transitions of Tm³⁺ ions, as well as weaker absorption bands corresponding to Tm²⁺ ions. The Judd–Ofelt (JO) formalism was applied to determine the intensity parameters Ω₂, Ω₄, and Ω₆, which were used to calculate radiative transition probabilities, branching ratios, and radiative lifetimes for the Tm³⁺ ions. The emission spectra showed concentration-dependent quenching effects, with significant emissions observed for the concentration of 0.1 mol% TmF₃ under excitation at 260 nm and 353 nm for Tm³⁺ ions and at 305 nm for Tm²⁺ ions. A new UV emission associated with divalent Thulium is reported. The results indicate that higher TmF₃ concentrations lead to increased non-radiative energy transfer, which reduces luminescence efficiency. These findings contribute to the understanding of the optical behavior of Tm-doped fluoride crystals, with implications for their application in laser technologies and radiation dosimetry. Full article

A glass composition using TeO₂-K₂TeO₃-Nb₂O₅-BaF₂ co-doped with Er₂O₃/Ho₂O₃ and Er₂O₃/Yb₂O₃ was successfully fabricated. Its thermal stability and physical parameters were studied, and luminescence spectroscopy of the fabricated glasses was conducted. The optical band gap, E_opt, decreased from 2.689 to 2.663 eV following the substitution of Ho₂O₃ with Yb₂O₃. The values of the refractive index, third-order nonlinear optical susceptibility (χ⁽³⁾), and nonlinear refractive index (n₂) of the fabricated glasses were estimated. Furthermore, the Judd–Ofelt intensity parameters ${\Omega }_t (t=2,4,6)$, radiative properties such as transition probabilities (A_ed), magnetic dipole-type transition probabilities (A_md), branching ratios (β), and radiative lifetime (τ) of the fabricated glasses were evaluated. The emission cross-section and FWHM of the ⁴I_13/2→⁴I_15/2 transition around 1.54 μm of the glass were reported, and the emission intensity of the visible signal was studied under 980 nm laser excitation. The material might be a useful candidate for solid lasers and nonlinear amplifier devices, especially in the communications bands. Full article

The thermal and optical properties of 60TeO₂-20K₂TeO₃-10WO₃-10Nb₂O₅ (in mol%) glasses doped with Ho₂O₃, Er₂O₃, and Tm₂O₃ were explored in the present work. The thermal stability, refractive index n, extinction coefficient k, absorption coefficient α, and optical band gap of the glasses were evaluated. The UV–Vis–NIR absorption spectra, the Judd–Ofelt intensity parameter, the spectroscopic quality factor, and the emission and absorption cross-sections were calculated to investigate the effects of Er³⁺ and Tm³⁺, respectively, on the band spectroscopic properties of Ho³⁺ ions. The results showed that the maximum emission cross-section was approximately $8\times {10}^{-21} {\mathrm{c}\mathrm{m}}^2$, and the values of the full width at half maximum ($FWHM)$, quality factor (${\sigma }_e\times FWHM)$, and gain coefficient of Ho³⁺: ⁵I₇$\to$⁵I₈ were also reported. The value of the $FWHM\times {\sigma }_e$ was $1200\times {10}^{-28} {\mathrm{c}\mathrm{m}}^3$, which showed greater gain characteristics than earlier study results. For $2 \mathsf{\mu }\mathrm{m}$ mid-infrared solid-state lasers, the glasses that were examined might be a good host material. Full article

A series of glasses based on (80-y) TeO₂-20 BiCl₃-y RE₂O₃ (y = 0, 0.6 mol%; RE = Nd, Sm, Dy, and Er) were prepared. The thermal stability of the glass was determined by differential scanning calorimetry (DSC). The density and optical energy values of the prepared glass increased in the order of Sm₂O₃, Nd₂O₃, Dy₂O₃, and Er₂O₃. In addition, the glass doped with Er₂O₃ had the highest refractive index values compared to the other samples. Subsequently, Judd–Ofelt parameters (Ω₂, Ω₄, and Ω₆) were obtained for the family of RE³⁺ trivalent rare-earth ions introduced as dopants in a tellurite glass. These parameters were calculated from the absorption spectra for each RE³⁺. The structures were studied by Raman spectroscopy deconvolution, which determined that TeO₄, TeO₃, TeO₃₊₁, BiO₆, and BiCl₆ units had formed. In addition, the structural changes in the glass are related to the intensity ratio of TeO₄/TeO₃, depending on the type of rare-earth. For the optics and Judd–Ofelt parameters, the ray spectroscopy results of the prepared glass show that it is a good candidate for nonlinear optics fibers, a solid laser material. Full article

Understanding the local environment of luminescent centers in phosphors serves as a blueprint for designing the luminescent properties of phosphors. Chemical substitution is a general strategy for engineering the local structure around luminescent center ions. In this study, we systematically investigate the luminescent properties of Ga-substituted Eu-doped CaYAlO₄ (CYAGO:Eu) phosphors and the local structure of the Eu ions. The Ga substitution at the Al sites leads to a significant enhancement in the electric dipole transition of Eu³⁺ (⁵D₀ → ⁷F₂). The Judd–Ofelt analysis reveals that Eu³⁺ ions are substituted for Ca/Y, and the Ga substitution increases the asymmetricity of the local structure around the Eu ions because of the different ionic radii and electronegativities of Al and Ga. In addition, Eu²⁺ emission is missing regardless of the Ga substitution and post-hydrogen treatments. The present work provides deeper insight into the role of chemical substitution in oxide phosphors. Full article

A new strategy for the easy polymerization of anionic [Ln(Q^cy)₄]⁻ (HQ^cy-4-(cyclohexanecarbonyl)-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one) into two-dimensional layers of [AgLn(Q^cy)₄]_n (Ln = Sm, Eu, Gd, Tb and Dy) is proposed by binding the single molecular anions [Ln(Q^cy)₄]⁻ to silver cations through the coordination of the pyridinic nitrogen atoms of the pyrazolonate rings. The luminescent properties of [AgLn(Q^cy)₄]_n have been studied in detail, and it was shown that the previously described low photoluminescence quantum yield (PLQY) of [Eu(Q^cy)₄]⁻ is due to Ligand-To-Metal Charge Transfer (LMCT) quenching, which is effectively suppressed in the heterometallic [AgEu(Q^cy)₄]_n polymer. Sensibilization coefficients for H₃O[Eu(Q^cy)₄], [AgEu(Q^cy)₄]_n, and H₃O[Sm(Q^cy)₄] complexes (n ≈ 1) were estimated via theoretical analysis (also by using Judd-Ofelt theory for Sm³⁺) and PLQY measurements. Full article

Borogermanate glasses singly doped with Dy³⁺ ions were synthesized and then studied using the absorption and luminescence spectra. Spectroscopic changes of Dy³⁺ ions have been examined for compositional-dependent glasses with various molar ratios GeO₂:B₂O₃. In this work, several spectroscopic parameters of Dy³⁺ ions were obtained experimentally and compared to the calculated values from the Judd–Ofelt theory. Luminescence spectra measured for borogermanate glasses consist of blue, yellow and red bands, which correspond to ⁴F_9/2 → ⁶H_15/2, ⁴F_9/2 → ⁶H_13/2 and ⁴F_9/2 → ⁶H_11/2 transitions of Dy³⁺, respectively. Luminescence lifetimes for the ⁴F_9/2 excited state are reduced, whereas the stimulated emission cross-sections for the most intense ⁴F_9/2 → ⁶H_13/2 yellow transition of Dy³⁺ increase with increasing GeO₂ and decreasing B₂O₃ concentrations in glass-hosts. Quantum efficiency of the ⁴F_9/2 (Dy³⁺) excited state is nearly independent on molar ratios GeO₂:B₂O₃. Attractive spectroscopic properties related to the ⁴F_9/2 → ⁶H_13/2 transition of Dy³⁺ ions are found for borogermanate glasses implying their potential utility for yellow laser action and solid-state lighting technology. Full article

Luminescent materials with high thermal stability and quantum efficiency are extensively desired for indoor illumination. In this research, a series of Eu³⁺-activated KGd₂F₇ red-emitting nanoparticles were prepared at room temperature and their phase structure, morphology, luminescence properties, as well as thermal stability, have been studied in detail. Excited by 393 nm, the resultant nanoparticles emitted bright red emissions and its optimal status was realized when the Eu³⁺ content was 30 mol%, in which the concentration quenching mechanism was triggered by electric dipole–dipole interaction. Through theoretical analysis via the Judd–Ofelt theory, one knows that Eu³⁺ situates at the high symmetry sites in as-prepared nanoparticles. Moreover, the internal and extra quantum efficiencies of designed nanoparticles were dependent on Eu³⁺ content. Furthermore, the studied nanoparticles also had splendid thermal stability and the corresponding activation energy was 0.18 eV. Additionally, via employing the designed nanoparticles as red-emitting constituents, a warm white light-emitting diode (white-LED), which exhibits low correlated color temperature (4456 K), proper luminous efficiency (17.2 lm/W) and high color rendering index (88.3), was developed. Our findings illustrate that Eu³⁺-activated KGd₂F₇ nanoparticles with bright red emissions are able to be used to promote the performance of white-LED. Full article