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7 pages, 292 KiB

Open AccessProceeding Paper

New Contribution to the Anomalous π⁰→γγ Decay in SU(2) Chiral Perturbation Theory

by Zhen-Yan Lu, Shu-Peng Wang and Qi Lu

Proceedings 2025, 123(1), 1; https://doi.org/10.3390/proceedings2025123001 - 28 Jul 2025

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The introduction of axions gives rise to additional one-loop diagrams for the two-photon decays of neutral pions via axion-pion mixing. We compute this correction that has been overlooked in existing calculations, within the framework of SU(2) chiral perturbation theory. Our analysis shows that [...] Read more.

The introduction of axions gives rise to additional one-loop diagrams for the two-photon decays of neutral pions via axion-pion mixing. We compute this correction that has been overlooked in existing calculations, within the framework of SU(2) chiral perturbation theory. Our analysis shows that the correction is proportional to the axion-photon coupling and the square of the axion mass. In the classical axion parameter space, this correction is strongly suppressed by the axion decay constant. However, for QCD axions in the MeV or higher mass range, the correction may become significant. Furthermore, when combined with experimental measurements of the decay width of the

π^{0} \to γ γ

process, our results rule out the standard QCD axion as a viable explanation for the observed discrepancy between chiral perturbation theory predictions and experimental data. Full article

(This article belongs to the Proceedings of The 5th International Conference on Symmetry (Symmetry 2025))

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11 pages, 3356 KiB

Open AccessArticle

Probing the pH Effect on Boehmite Particles in Water Using Vacuum Ultraviolet Single-Photon Ionization Mass Spectrometry

by Xiao Sui, Bo Xu and Xiao-Ying Yu

Int. J. Mol. Sci. 2025, 26(15), 7254; https://doi.org/10.3390/ijms26157254 - 27 Jul 2025

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Abstract

Boehmite has been widely used in theoretical research and industry, especially for hazardous material processing. For the liquid-phase treating process, the interfacial properties of boehmite are believed to be affected by pH conditions, which change its physicochemical behavior. However, molecular-level detection on cluster [...] Read more.

Boehmite has been widely used in theoretical research and industry, especially for hazardous material processing. For the liquid-phase treating process, the interfacial properties of boehmite are believed to be affected by pH conditions, which change its physicochemical behavior. However, molecular-level detection on cluster ions is challenging when using bulk approaches. Herein we employ in situ vacuum ultraviolet single-photon ionization mass spectrometry (VUV SPI-MS) coupled with a vacuum-compatible microreactor system for analysis at the liquid–vacuum interface (SALVI) to investigate the solute molecular composition of boehmite under different pH conditions for the first time. The mass spectral results show that more complex clustering of solute molecules exists at the solid–liquid (s–l) interface than conventionally perceived in a “simple” aqueous solution. Besides solute ions, such as boehmite molecules and fragments, the composition and appearance energies of these newly discovered solvated cluster ions are determined by VUV SPI-MS in different pH solutions. We offer new results for the pH-dependent effect of boehmite and provide insights into a more detailed solvation mechanism at the s–l interface. By comparing the key products under different pH conditions, fundamental understanding of boehmite dissolution is revealed to assist the engineering design of waste processing and storage solutions. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems, 6th Edition)

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17 pages, 3191 KiB

Open AccessArticle

Optimizing Graphene Ring Modulators: A Comparative Study of Straight, Bent, and Racetrack Geometries

by Pawan Kumar Dubey, Ashraful Islam Raju, Rasuole Lukose, Christian Wenger and Mindaugas Lukosius

Nanomaterials 2025, 15(15), 1158; https://doi.org/10.3390/nano15151158 - 27 Jul 2025

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Abstract

Graphene-based micro-ring modulators are promising candidates for next-generation optical interconnects, offering compact footprints, broadband operation, and CMOS compatibility. However, most demonstrations to date have relied on conventional straight bus coupling geometries, which limit design flexibility and require extremely small coupling gaps to reach [...] Read more.

Graphene-based micro-ring modulators are promising candidates for next-generation optical interconnects, offering compact footprints, broadband operation, and CMOS compatibility. However, most demonstrations to date have relied on conventional straight bus coupling geometries, which limit design flexibility and require extremely small coupling gaps to reach critical coupling. This work presents a comprehensive comparative analysis of straight, bent, and racetrack bus geometries in graphene-on-silicon nitride (Si₃N₄) micro-ring modulators operating near 1.31 µm. Based on finite-difference time-domain simulation results, a proposed racetrack-based modulator structure demonstrates that extending the coupling region enables critical coupling at larger gaps—up to 300 nm—while preserving high modulation efficiency. With only 6–12% graphene coverage, this geometry achieves extinction ratios of up to 28 dB and supports electrical bandwidths approaching 90 GHz. Findings from this work highlight a new co-design framework for coupling geometry and graphene coverage, offering a pathway to high-speed and high-modulation-depth graphene photonic modulators suitable for scalable integration in next-generation photonic interconnects devices. Full article

(This article belongs to the Special Issue 2D Materials for High-Performance Optoelectronics)

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17 pages, 1725 KiB

Open AccessArticle

Ring Opening upon Valence Shell Excitation in β-Butyrolactone: Experimental and Theoretical Methods

by Pedro A. S. Randi, Márcio H. F. Bettega, Nykola C. Jones, Søren V. Hoffmann, Małgorzata A. Śmiałek and Paulo Limão-Vieira

Molecules 2025, 30(15), 3137; https://doi.org/10.3390/molecules30153137 (registering DOI) - 26 Jul 2025

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Abstract

The valence-shell electronic state spectroscopy of β-butyrolactone (CH₃CHCH₂CO₂) is comprehensively investigated by employing experimental and theoretical methods. We report a novel vacuum ultraviolet (VUV) absorption spectrum in the photon wavelength range from 115 to 320 nm (3.9–10.8 [...] Read more.

The valence-shell electronic state spectroscopy of β-butyrolactone (CH₃CHCH₂CO₂) is comprehensively investigated by employing experimental and theoretical methods. We report a novel vacuum ultraviolet (VUV) absorption spectrum in the photon wavelength range from 115 to 320 nm (3.9–10.8 eV), together with ab initio quantum chemical calculations at the time-dependent density functional (TD-DFT) level of theory. The dominant electronic excitations are assigned to mixed valence-Rydberg and Rydberg transitions. The fine structure in the CH₃CHCH₂CO₂ photoabsorption spectrum has been assigned to C=O stretching,

v_{7}^{'} (a)

, CH₂ wagging,

v_{14}^{'} (a)

, C–O stretching,

v_{22}^{'} (a)

, and C=O bending,

v_{26}^{'} (a)

modes. Photolysis lifetimes in the Earth’s atmosphere from 0 km up to 50 km altitude have been estimated, showing to be a non-relevant sink mechanism compared to reactions with the ^•OH radical. The nuclear dynamics along the C=O and C–C–C coordinates have been investigated at the TD-DFT level of theory, where, upon electronic excitation, the potential energy curves show important carbonyl bond breaking and ring opening, respectively. Within such an intricate molecular landscape, the higher-lying excited electronic states may keep their original Rydberg character or may undergo Rydberg-to-valence conversion, with vibronic coupling as an important mechanism contributing to the spectrum. Full article

(This article belongs to the Special Issue Advances in Density Functional Theory (DFT) Calculation)

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14 pages, 3769 KiB

Open AccessArticle

Inversely Designed Silicon Nitride Power Splitters with Arbitrary Power Ratios

by Yang Cong, Shuo Liu, Yanfeng Liang, Haoyu Wang, Huanlin Lv, Fangxu Liu, Xuanchen Li and Qingxiao Guo

Photonics 2025, 12(8), 744; https://doi.org/10.3390/photonics12080744 - 24 Jul 2025

Viewed by 191

Abstract

An optical power splitter (OPS) with arbitrary splitting ratios has attracted significant research interest for its broad applications in photonic integrated circuits. A series of OPSs with arbitrary splitting ratios based on silicon nitride (Si₃N₄) platforms are presented. The [...] Read more.

An optical power splitter (OPS) with arbitrary splitting ratios has attracted significant research interest for its broad applications in photonic integrated circuits. A series of OPSs with arbitrary splitting ratios based on silicon nitride (Si₃N₄) platforms are presented. The devices are designed with ultra-compact dimensions using three-dimensional finite-difference time-domain (3D FDTD) analysis and an inverse design algorithm. Within a 50 nm bandwidth (1525 nm to 1575 nm), we demonstrated a 1 × 2 OPS with splitting ratios of 1:1, 1:1.5, and 1:2; a 1 × 3 OPS with ratios of 1:2:1 and 2:1:2; and a 1 × 4 OPS with ratios of 1:1:1:1 and 2:1:2:1. The target splitting ratios are achieved by optimizing pixel distributions in the coupling region. The dimensions of the designed devices are 1.96 × 1.96 µm², 2.8 × 2.8 µm², and 2.8 × 4.2 µm², respectively. The designed devices achieve transmission efficiencies exceeding 90% and exhibit excellent power splitting ratios (PSRs). Full article

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25 pages, 1566 KiB

Open AccessArticle

Combining QSAR and Molecular Docking for the Methodological Design of Novel Radiotracers Targeting Parkinson’s Disease

by Juan A. Castillo-Garit, Mar Soria-Merino, Karel Mena-Ulecia, Mónica Romero-Otero, Virginia Pérez-Doñate, Francisco Torrens and Facundo Pérez-Giménez

Appl. Sci. 2025, 15(15), 8134; https://doi.org/10.3390/app15158134 - 22 Jul 2025

Viewed by 231

Abstract

Parkinson’s disease (PD) is a neurodegenerative disorder marked by the progressive loss of dopaminergic neurons in the nigrostriatal pathway. The dopamine active transporter (DAT), a key protein involved in dopamine reuptake, serves as a selective biomarker for dopaminergic terminals in the striatum. DAT [...] Read more.

Parkinson’s disease (PD) is a neurodegenerative disorder marked by the progressive loss of dopaminergic neurons in the nigrostriatal pathway. The dopamine active transporter (DAT), a key protein involved in dopamine reuptake, serves as a selective biomarker for dopaminergic terminals in the striatum. DAT binding has been extensively studied using in vivo imaging techniques such as Single-Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET). To support the design of new radiotracers targeting DAT, we employ Quantitative Structure–Activity Relationship (QSAR) analysis on a structurally diverse dataset composed of 57 compounds with known affinity constants for DAT. The best-performing QSAR model includes four molecular descriptors and demonstrates robust statistical performance: R² = 0.7554, Q²_LOO = 0.6800, and external R² = 0.7090. These values indicate strong predictive capability and model stability. The predicted compounds are evaluated using a docking methodology to check the correct coupling and interactions with the DAT. The proposed approach—combining QSAR modeling and docking—offers a valuable strategy for screening and optimizing potential PET/SPECT radiotracers, ultimately aiding in the neuroimaging and early diagnosis of Parkinson’s disease. Full article

(This article belongs to the Special Issue Application of Artificial Intelligence in Biomedical Informatics)

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19 pages, 431 KiB

Open AccessArticle

The Detection of a Defect in a Dual-Coupling Optomechanical System

by Zhen Li and Ya-Feng Jiao

Symmetry 2025, 17(7), 1166; https://doi.org/10.3390/sym17071166 - 21 Jul 2025

Viewed by 203

Abstract

We provide an approach to detect a nitrogen-vacancy (NV) center, which might be a defect in a diamond nanomembrane, using a dual-coupling optomechanical system. The NV center modifies the energy-level structure of a dual-coupling optomechanical system through dressed states arising from its interaction [...] Read more.

We provide an approach to detect a nitrogen-vacancy (NV) center, which might be a defect in a diamond nanomembrane, using a dual-coupling optomechanical system. The NV center modifies the energy-level structure of a dual-coupling optomechanical system through dressed states arising from its interaction with the mechanical membrane. Thus, we study the photon blockade in the cavity of a dual-coupling optomechanical system in which an NV center is embedded in a single-crystal diamond nanomembrane. The NV center significantly influences the statistical properties of the cavity field. We systematically investigate how three key NV center parameters affect photon blockade: (i) its coupling strength to the mechanical membrane, (ii) transition frequency, and (iii) decay rate. We find that the NV center can shift, give rise to a new dip, and even suppress the original dip in a bare quadratic optomechanical system. In addition, we can amplify the effect of the NV center on photon statistics by adding a gravitational potential when the NV center has little effect on photon blockade. Therefore, our study provides a method to detect diamond nanomembrane defects in a dual-coupling optomechanical system. Full article

(This article belongs to the Section Physics)

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15 pages, 3554 KiB

Open AccessArticle

A Composite Substrate of Ag Nanoparticle-Decorated Inverse Opal Polydimethylsiloxane for Surface Raman Fluorescence Dual Enhancement

by Zilun Tang, Hongping Liang, Zhangyang Chen, Jianpeng Li, Jianyu Wu, Xianfeng Li and Dingshu Xiao

Polymers 2025, 17(14), 1995; https://doi.org/10.3390/polym17141995 - 21 Jul 2025

Viewed by 302

Abstract

It is difficult to simultaneously achieve surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF) for noble metals. Herein, a composite substrate is demonstrated based on the rational construction of Ag nanoparticles (Ag NPs) and inverse opal polydimethylsiloxane (PDMS) for surface Raman fluorescence dual [...] Read more.

It is difficult to simultaneously achieve surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF) for noble metals. Herein, a composite substrate is demonstrated based on the rational construction of Ag nanoparticles (Ag NPs) and inverse opal polydimethylsiloxane (PDMS) for surface Raman fluorescence dual enhancement. The well-designed Ag nanoparticle (Ag NP)-decorated inverse opal PDMS (AIOP) composite substrate is fabricated using the polystyrene (PS) photonic crystal method and the sensitization reduction technique. The inverse opal PDMS enhances the electromagnetic (EM) field by increasing the loading of Ag NPs and plasmonic coupling of Ag NPs, leading to SERS activity. The thin shell layer of polyvinyl pyrrolidone (PVP) in core–shell Ag NPs isolates the detected molecule from the Ag core to prevent the fluorescence resonance energy transfer and charge transfer to eliminate fluorescence quenching and enable SEF performance. Based on the blockage of the core–shell structure and the enhanced EM field originating from the inverse opal structure, the as-fabricated AIOP composite substrate shows dual enhancement in surface Raman fluorescence. The AIOP composite substrate in this work, which combines improved SERS activity and SEF performance, not only promotes the development of surface-enhanced spectroscopy but also shows promise for applications in flexible sensors. Full article

(This article belongs to the Special Issue Polymer-Based Flexible Materials, 3rd Edition)

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13 pages, 617 KiB

Open AccessProject Report

European Partnership in Metrology Project: Photonic and Quantum Sensors for Practical Integrated Primary Thermometry (PhoQuS-T)

by Olga Kozlova, Rémy Braive, Tristan Briant, Stéphan Briaudeau, Paulina Castro Rodríguez, Guochun Du, Tufan Erdoğan, René Eisermann, Emile Ferreux, Dario Imbraguglio, Judith Elena Jordan, Stephan Krenek, Graham Machin, Igor P. Marko, Théo Martel, Maria Jose Martin, Richard A. Norte, Laurent Pitre, Sara Pourjamal, Marco Queisser, Israel Rebolledo-Salgado, Iago Sanchez, Daniel Schmid, Cliona Shakespeare, Fernando Sparasci, Peter G. Steeneken, Tatiana Steshchenko, Stephen J. Sweeney, Shahin Tabandeh, Georg Winzer, Anoma Yamsiri, Alethea Vanessa Zamora Gómez, Martin Zelan and Lars Zimmermann Show full author list Hide full author list

Metrology 2025, 5(3), 44; https://doi.org/10.3390/metrology5030044 - 19 Jul 2025

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Abstract

Current temperature sensors require regular recalibration to maintain reliable temperature measurement. Photonic/quantum-based approaches have the potential to radically change the practice of thermometry through provision of in situ traceability, potentially through practical primary thermometry, without the need for sensor recalibration. This article gives [...] Read more.

Current temperature sensors require regular recalibration to maintain reliable temperature measurement. Photonic/quantum-based approaches have the potential to radically change the practice of thermometry through provision of in situ traceability, potentially through practical primary thermometry, without the need for sensor recalibration. This article gives an overview of the European Partnership in Metrology (EPM) project: Photonic and quantum sensors for practical integrated primary thermometry (PhoQuS-T), which aims to develop sensors based on photonic ring resonators and optomechanical resonators for robust, small-scale, integrated, and wide-range temperature measurement. The different phases of the project will be presented. The development of the integrated optical practical primary thermometer operating from 4 K to 500 K will be reached by a combination of different sensing techniques: with the optomechanical sensor, quantum thermometry below 10 K will provide a quantum reference for the optical noise thermometry (operating in the range 4 K to 300 K), whilst using the high-resolution photonic (ring resonator) sensor the temperature range to be extended from 80 K to 500 K. The important issues of robust fibre-to-chip coupling will be addressed, and application case studies of the developed sensors in ion-trap monitoring and quantum-based pressure standards will be discussed. Full article

(This article belongs to the Special Issue Measuring by Light: Innovations in Optical Measurement and Sensing for Advanced Metrology)

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10 pages, 1632 KiB

Open AccessArticle

An Ultra-Narrowband Graphene-Perfect Absorber Based on Bound States in the Continuum of All-Dielectric Metasurfaces

by Qi Zhang, Xiao Zhang, Zhihong Zhu and Chucai Guo

Nanomaterials 2025, 15(14), 1124; https://doi.org/10.3390/nano15141124 - 19 Jul 2025

Viewed by 296

Abstract

Enhancing light absorption in two-dimensional (2D) materials, particularly few-layer structures, is critical for advancing optoelectronic devices such as light sources, photodetectors, and sensors. However, conventional absorption enhancement strategies often suffer from unstable resonant wavelengths and low-quality factors (Q-factors) due to the inherent weak [...] Read more.

Enhancing light absorption in two-dimensional (2D) materials, particularly few-layer structures, is critical for advancing optoelectronic devices such as light sources, photodetectors, and sensors. However, conventional absorption enhancement strategies often suffer from unstable resonant wavelengths and low-quality factors (Q-factors) due to the inherent weak light–matter interactions in 2D materials. To address these limitations, we propose an all-dielectric metasurface graphene-perfect absorber based on toroidal dipole bound state in the continuum (TD-BIC) with an ultra-narrow bandwidth and stable resonant wavelength. The proposed structure achieves tunable absorption linewidths spanning three orders of magnitude (6 nm to 0.0076 nm) through critical coupling modulation. Furthermore, the operational wavelength can be flexibly extended to any near-infrared region by adjusting the grating width. This work establishes a novel paradigm for enhancing the absorption of 2D materials in photonic device applications. Full article

(This article belongs to the Special Issue Two-Dimensional Materials and Metamaterials in Photonics and Optoelectronics (Second Edition))

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15 pages, 2929 KiB

Open AccessArticle

Graphene-Loaded LiNbO₃ Directional Coupler: Characteristics and Potential Applications

by Yifan Liu, Fei Lu, Hui Hu, Haoyang Du, Yan Liu and Yao Wei

Nanomaterials 2025, 15(14), 1116; https://doi.org/10.3390/nano15141116 - 18 Jul 2025

Viewed by 283

Abstract

This study explores the impact of graphene integration on lithium niobate (LiNbO₃, LN) ridge waveguides and directional couplers, focusing on coupling efficiency, polarization-dependent light absorption, and temperature sensitivity. Experimental and simulation results reveal that graphene loading significantly alters the effective mode [...] Read more.

This study explores the impact of graphene integration on lithium niobate (LiNbO₃, LN) ridge waveguides and directional couplers, focusing on coupling efficiency, polarization-dependent light absorption, and temperature sensitivity. Experimental and simulation results reveal that graphene loading significantly alters the effective mode refractive index and enhances waveguide coupling, enabling precise control over light transmission and power distribution. The temperature-dependent behavior of graphene–LN structures demonstrates strong thermal sensitivity, with notable changes in output power ratios between cross and through ports under varying temperatures. These findings highlight the potential of graphene–LN hybrid devices for compact, high-performance photonic circuits and temperature sensing applications. This study provides valuable insights into the design of advanced integrated photonic systems, paving the way for innovations in optical communication, sensing, and quantum technologies. Full article

(This article belongs to the Special Issue Photonics/Optoelectronics Properties and Applications of Two-Dimensional Heterostructures)

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14 pages, 8428 KiB

Open AccessArticle

Spin-Orbit-Coupling-Governed Optical Absorption in Bilayer MoS₂ via Strain, Twist, and Electric Field Engineering

by Lianmeng Yu, Yingliang Chen, Weibin Zhang, Peizhi Yang and Xiaobo Feng

Nanomaterials 2025, 15(14), 1100; https://doi.org/10.3390/nano15141100 - 16 Jul 2025

Viewed by 277

Abstract

This paper investigates strain-, twist-, and electric-field-tuned optical absorption in bilayer MoS₂, emphasizing spin-orbit coupling (SOC). A continuum model reveals competing mechanisms: geometric perturbations (strain/twist) and Stark effects govern one-/two-photon absorption, with critical thresholds (~9% strain, ~2.13° twist) switching spin-independent to [...] Read more.

This paper investigates strain-, twist-, and electric-field-tuned optical absorption in bilayer MoS₂, emphasizing spin-orbit coupling (SOC). A continuum model reveals competing mechanisms: geometric perturbations (strain/twist) and Stark effects govern one-/two-photon absorption, with critical thresholds (~9% strain, ~2.13° twist) switching spin-independent to spin-polarized regimes. Strain gradients and twist enhance nonlinear responses through symmetry-breaking effects while electric fields dynamically modulate absorption via band alignment tuning. By linking parameter configurations to absorption characteristics, this work provides a framework for designing tunable spin-resolved optoelectronic devices and advancing light–matter control in 2D materials. Full article

(This article belongs to the Special Issue Structural Modeling and Theoretical Study of Low-Dimensional Materials)

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11 pages, 11723 KiB

Open AccessArticle

Spectrally Resolved Dynamics of Delayed Luminescence in Dense Scattering Media

by Mahshid Zoghi, Ernesto Jimenez-Villar and Aristide Dogariu

Materials 2025, 18(13), 3194; https://doi.org/10.3390/ma18133194 - 6 Jul 2025

Viewed by 338

Abstract

Highly scattering media have garnered significant interest in recent years, ranging from potential applications in solar cells, photocatalysis, and other novel photonic devices to research on fundamental topics such as topological photonics, enhanced light–matter coupling and light confinement. Here, we report measurements of [...] Read more.

Highly scattering media have garnered significant interest in recent years, ranging from potential applications in solar cells, photocatalysis, and other novel photonic devices to research on fundamental topics such as topological photonics, enhanced light–matter coupling and light confinement. Here, we report measurements of spectrally and time-resolved delayed luminescence (DL) in highly scattering rutile TiO₂ films. The complex emission kinetics manifests in the non-exponential decay of photon density and the temporal evolution of the spectral composition. We found that while the energy levels of TiO₂ nanoparticles broadly set the spectral regions of excitation and emission, our results demonstrate that the DL intensity and duration are strongly influenced by the inherent multiple elastic and inelastic processes determined by the mesoscale inhomogeneous structure of random media. We show that the lifetime of DL increases up to 6 s for the largest redshift detected, which is associated with multiple reabsorption processes. We outline a simple model for spectrally resolved DL emission from dense scattering media that can guide the design and characterization of composite materials with specific spectral and temporal properties. Full article

(This article belongs to the Section Smart Materials)

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18 pages, 3893 KiB

Open AccessArticle

Creation of Low-Loss Dual-Ring Optical Filter via Temporal Coupled Mode Theory and Direct Binary Search Inverse Design

by Yuchen Hu, Tong Wang, Wen Zhou and Bo Hu

Photonics 2025, 12(7), 681; https://doi.org/10.3390/photonics12070681 - 6 Jul 2025

Viewed by 270

Abstract

We propose a dual-ring optical filter based on direct binary search inverse design. The proposed device comprises two cascaded rings in an add–drop configuration. A physical model was established using temporal coupled mode theory to derive theoretical spectra and analyze key parameters governing [...] Read more.

We propose a dual-ring optical filter based on direct binary search inverse design. The proposed device comprises two cascaded rings in an add–drop configuration. A physical model was established using temporal coupled mode theory to derive theoretical spectra and analyze key parameters governing transmission performance. Based on theoretical results, a direct binary search algorithm was implemented. The parameters of the proposed device were calculated using a three-dimensional finite-difference time-domain method for verification. The numerical results demonstrate a free spectral range of 86 nm, with insertion loss and extinction ratios of 0.3 dB and 22 dB, respectively. The proposed device has a narrow spectral linewidth of 0.3 nm within a compact footprint of

24 μ m \times 25.5 μ m

. The device shows significant application potential in laser external cavities and dense wavelength division multiplexing systems. Moreover, this work provides a novel methodology for precision design of photonic devices. Full article

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15 pages, 7120 KiB

Open AccessArticle

A Dynamic Analysis of Toron Formation in Chiral Nematic Liquid Crystals Using a Polarization Holographic Microscope

by Tikhon V. Reztsov, Aleksey V. Chernykh, Tetiana Orlova and Nikolay V. Petrov

Polymers 2025, 17(13), 1849; https://doi.org/10.3390/polym17131849 - 2 Jul 2025

Viewed by 382

Abstract

Topological orientation structures in chiral nematic liquid crystals, such as torons, exhibit promising optical properties and are of increasing interest for applications in photonic devices. However, despite this attention, their polarization and phase dynamics during formation remain insufficiently explored. In this work, we [...] Read more.

Topological orientation structures in chiral nematic liquid crystals, such as torons, exhibit promising optical properties and are of increasing interest for applications in photonic devices. However, despite this attention, their polarization and phase dynamics during formation remain insufficiently explored. In this work, we investigate the dynamic optical response of a toron generated by focused femtosecond infrared laser pulses. A custom-designed polarization holographic microscope is employed to simultaneously record four polarization-resolved interferograms in a single exposure. This enables the real-time reconstruction of the Jones matrix, providing a complete description of the local polarization transformation introduced by the formation of the topological structure. The study demonstrates that torons can facilitate spin–orbit coupling of light in a manner analogous to q-plates, highlighting their potential for advanced vector beam shaping and topological photonics applications. Full article

(This article belongs to the Section Polymer Physics and Theory)

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