Photonics

10 pages, 5013 KB

Open AccessCommunication

Sandwich-Multilayer-Film Perfect Absorber Spanning the Entire Visible Spectrum

by Xuan Zou, Hong Li, Yijia Huang, Ling Li and Jie Zheng

Photonics 2026, 13(7), 652; https://doi.org/10.3390/photonics13070652 (registering DOI) - 5 Jul 2026

High-efficiency perfect absorption, spanning the entire visible region, plays an increasingly significant role in applications such as solar energy harvesting, photodetection, and thermal radiation management. However, the complexity and manufacturing difficulty of the currently proposed structures hinder large-scale application. In this work, we [...] Read more.

High-efficiency perfect absorption, spanning the entire visible region, plays an increasingly significant role in applications such as solar energy harvesting, photodetection, and thermal radiation management. However, the complexity and manufacturing difficulty of the currently proposed structures hinder large-scale application. In this work, we propose a broadband perfect absorber based on a tungsten–silicon nitride–tungsten (W-Si₃N₄-W) sandwich multilayer film. We combine the unique broadband absorption capability and high-temperature stability of material W with the low-loss characteristic of material Si₃N₄. By optimizing the geometrical parameters of the structure, we successfully achieved an average absorption efficiency exceeding 94% across a wide wavelength ranging from 500 nm to 900 nm. This work paves the way for developing high-performance, stable, and broadband absorption devices. Full article

(This article belongs to the Special Issue Advances in Micro-Nano Optical Manufacturing)

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11 pages, 2529 KB

Open AccessArticle

Numerical Investigation of Transient Mode-Locking Dynamics in a SESAM-Based Yb-Doped Picosecond Fiber Laser

by Yufei Mao, Yuyan Zhao, Jiancheng Zheng and Chibiao Liu

Photonics 2026, 13(7), 651; https://doi.org/10.3390/photonics13070651 (registering DOI) - 5 Jul 2026

Abstract

This study investigates the transient mode-locking dynamics and parameter-sensitive pulse evolution in a ytterbium-doped mode-locked fiber laser under near-zero net-dispersion conditions. The influence of gain saturation energy E_s, modulation depth T₀, saturation power P_sat, and non-saturable loss [...] Read more.

This study investigates the transient mode-locking dynamics and parameter-sensitive pulse evolution in a ytterbium-doped mode-locked fiber laser under near-zero net-dispersion conditions. The influence of gain saturation energy E_s, modulation depth T₀, saturation power P_sat, and non-saturable loss P_ns on transient pulse evolution and mode-locking buildup is comparatively analyzed using the complex Ginzburg–Landau equation. Numerical results indicate that increasing the gain saturation energy E_s weakens the gain saturation effect and prolongs the transient buildup process of stable mode locking, while simultaneously promoting intracavity energy accumulation and spectral broadening through enhanced nonlinear phase evolution. Increasing the modulation depth T₀ accelerates mode-locking initiation through enhanced nonlinear transmission contrast, whereas saturation power P_sat mainly affects the transient intracavity energy accumulation process during pulse evolution. Increasing the non-saturable loss P_ns suppresses low-intensity fluctuations during pulse buildup and contributes to faster gain–loss stabilization inside the laser cavity. Under near-zero net-dispersion conditions, stable picosecond pulse evolution with consistent spectral and temporal characteristics is numerically obtained. The present results provide useful physical insight into gain–loss interaction mechanisms and transient dissipative-soliton dynamics in ultrafast fiber lasers. Full article

(This article belongs to the Section Lasers, Light Sources and Sensors)

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65 pages, 4018 KB

Open AccessReview

Recent Developments in Single-Photon Avalanche Diode (SPAD) Technologies: From Device Engineering to Optimized Photonic Performance in Quantum Communication

by Masoud Abrari, Seyyedeh Tahereh Sajjadian, Parsa Nedaei and Majid Ghanaatshoar

Photonics 2026, 13(7), 650; https://doi.org/10.3390/photonics13070650 (registering DOI) - 4 Jul 2026

Abstract

The ability to detect individual photons with exquisite temporal precision has transformed single-photon avalanche diodes (SPADs) into indispensable tools across photonics, with quantum communication emerging as one of their most demanding frontiers. In recent years, device engineering breakthroughs, including refined junction geometries, advanced [...] Read more.

The ability to detect individual photons with exquisite temporal precision has transformed single-photon avalanche diodes (SPADs) into indispensable tools across photonics, with quantum communication emerging as one of their most demanding frontiers. In recent years, device engineering breakthroughs, including refined junction geometries, advanced avalanche quenching schemes and scalable array integration, have redefined the limits of SPAD performance. Parallel advances in fabrication precision and CMOS-compatible architectures have not only expanded spectral sensitivity from the visible to the near-infrared but also enabled systematic suppression of dark count rates, afterpulsing, and timing jitter. These developments have directly impacted the feasibility and robustness of quantum key distribution and time-correlated single-photon counting, where detection efficiency and noise suppression determine system fidelity. This review unifies recent progress in SPAD technology, weaving together innovations in device design, fabrication strategies, and parameter optimization to reveal their collective influence on next-generation quantum-enabled photonic systems. Looking forward, the convergence of hybrid material platforms, on-chip photonic–electronic co-integration, and intelligent quenching control is poised to elevate SPAD performance to meet, and potentially exceed, the stringent requirements of future quantum communication infrastructures. Full article

(This article belongs to the Special Issue Recent Progress in Optical Quantum Information and Communication)

21 pages, 2528 KB

Open AccessArticle

Improving Precision in Extended-Range Three-Dimensional Single-Molecule Localization with Physics-Guided Deep Learning

by Xiang Zhou, Yuma Ito and Makio Tokunaga

Photonics 2026, 13(7), 649; https://doi.org/10.3390/photonics13070649 - 3 Jul 2026

Abstract

Extended-range three-dimensional (3D) single-molecule localization microscopy (SMLM) and single-particle tracking (SPT) require precise emitter localization across cellular-scale axial distances. However, long-rangeengineered point-spread functions (PSFs) spread photons over wider camera footprints, lowering the signal-to-noise ratio (SNR) and localization precision. We numerically evaluated a physics-guided [...] Read more.

Extended-range three-dimensional (3D) single-molecule localization microscopy (SMLM) and single-particle tracking (SPT) require precise emitter localization across cellular-scale axial distances. However, long-rangeengineered point-spread functions (PSFs) spread photons over wider camera footprints, lowering the signal-to-noise ratio (SNR) and localization precision. We numerically evaluated a physics-guided deep learning workflow for 3D localization over a 10.0 µm axial range using simulated electron-multiplying charge-coupled device (EMCCD) images. The workflow combines an analytical secondary-astigmatism phase mask, frequency-domain cross-filtering, a cross-filtering generative adversarial network (CFGAN), and coarse-to-fine fitting. The optical model and engineered PSF provide physical signal priors, cross-filtering preserves directional Fourier-domain energy, and CFGAN suppresses residual structured noise before model-based localization. In low-SNR simulations, lateral, axial, and radial root-mean-squared localization errors (RMSEs) decreased from 54.11, 96.12, and 112.79 nm without denoising to 31.14, 39.06, and 50.12 nm after CFGAN denoising—close to Cramér–Rao lower-bound (CRLB) references of 34.39, 38.94, and 51.95 nm. High-SNR RMSE values were 8.78, 12.00, and 14.96 nm, comparable to CRLB references of 10.36, 11.71, and 15.64 nm. These simulations suggest that physics-guided restoration can improve extended-range 3D SMLM precision, while experimental validation remains necessary. Full article

(This article belongs to the Special Issue Deep Learning in Optical Engineering: Applications in Design, Simulation, and Performance)

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16 pages, 3467 KB

Open AccessArticle

Robust Four-Wavelength Achromatic Metalens Design for Long Wave Infrared Multispectral Focusing

by Junya Wang, Jun Chang, Ting Zheng and Yanhong Xie

Photonics 2026, 13(7), 648; https://doi.org/10.3390/photonics13070648 - 3 Jul 2026

Abstract

Long wave infrared metalenses provide a promising route toward compact multispectral optical systems, including spaceborne imaging and sensing payloads. However, achromatic focusing at separated LWIR wavelength channels remains challenging because the required phase relation must be maintained together with sufficient dispersion control and [...] Read more.

Long wave infrared metalenses provide a promising route toward compact multispectral optical systems, including spaceborne imaging and sensing payloads. However, achromatic focusing at separated LWIR wavelength channels remains challenging because the required phase relation must be maintained together with sufficient dispersion control and optical throughput. Here, we propose a robust four-wavelength achromatic metalens operating at 8, 10, 12, and 14

μ

m based on a meta-atom library controlled by nanopillar radius and height. The library feasibility is evaluated before layout optimization to verify whether the required phase and dispersion responses are accessible within the selected unit cell space. By introducing nanopillar height as an additional degree of freedom, the library achieves a phase coverage ratio above 0.92 at all four wavelengths. The optimized metalens achieves a mean absolute focusing efficiency (AFE) of 69.5% with suppressed chromatic focal shift. Monte Carlo perturbation analysis and full device FDTD simulations further confirm the robustness and focusing stability of the design. This work provides a feasibility-driven strategy for robust multispectral LWIR achromatic metalenses. Full article

(This article belongs to the Special Issue Advances in Micro-Nano Optical Manufacturing)

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16 pages, 1045 KB

Open AccessArticle

Comparative Study of the O–U-Band Transmission Performance of Different Optical Fiber Links Based on the GN Model

by Bingyan Shan, Jingyang Tian, Xiaojian Li, Qianle Huang, Mengfei Huo and Bing Lei

Photonics 2026, 13(7), 647; https://doi.org/10.3390/photonics13070647 - 2 Jul 2026

Abstract

As the available spectrum in the conventional C band becomes increasingly limited, ultra-wideband transmission across the O–U wavelength range (1260–1675 nm) provides a promising approach to increasing optical fiber link capacity. To support performance evaluation and preliminary fiber-link selection, this study compares standard [...] Read more.

As the available spectrum in the conventional C band becomes increasingly limited, ultra-wideband transmission across the O–U wavelength range (1260–1675 nm) provides a promising approach to increasing optical fiber link capacity. To support performance evaluation and preliminary fiber-link selection, this study compares standard single-mode fiber (SMF), pure-silica-core fiber (PSCF), and hollow-core fiber (HCF) links across the O–U bands. A transmission-performance analysis framework was established based on the Gaussian noise (GN) model. Band-specific amplifier parameters and fiber-specific span configurations were incorporated to evaluate transmission reach, optimum launch power, and theoretical capacity. Auxiliary simulations were conducted using VPIphotonics Design Suite 11.1 (VPIphotonics GmbH, Berlin, Germany) for representative C-band cases to examine the consistency of the overall trends predicted by the theoretical analysis. The GN-model analysis and auxiliary simulations show consistent overall trends, indicating that the GN model can serve as a computationally efficient tool for comparative link assessment and preliminary fiber-link selection. Under the unified analytical framework and consistently defined engineering constraints, PSCF offers a clear transmission-reach advantage over conventional SMF, whereas HCF shows greater theoretical power tolerance and capacity potential under the adopted representative parameter assumptions. Under the adopted non-saturated reference operating conditions, the per-channel capacity of HCF is approximately 34–54% higher than that of SMF in the S, C, L, and U bands and also clearly exceeds that of PSCF. These HCF results should be interpreted as model-based theoretical estimates, since practical performance may be affected by loss, dispersion uncertainty, splice/connector loss, bending sensitivity, and mode coupling. Full article

(This article belongs to the Section Optical Communication and Network)

12 pages, 1745 KB

Open AccessArticle

Reservoir Computing Using an Electroabsorption Modulated Laser-Based Optoelectronic Oscillator

by Jiuchang Peng, Juanjuan Yan and Rufei Zhang

Photonics 2026, 13(7), 646; https://doi.org/10.3390/photonics13070646 - 2 Jul 2026

Abstract

Reservoir computing (RC) is a simple and highly efficient artificial neural network. For such a network, only the output connection weights need training, effectively reducing computational complexity. Optoelectronic time-delayed RC is typically based on an optoelectronic oscillator (OEO) with simultaneous broadband processing capabilities [...] Read more.

Reservoir computing (RC) is a simple and highly efficient artificial neural network. For such a network, only the output connection weights need training, effectively reducing computational complexity. Optoelectronic time-delayed RC is typically based on an optoelectronic oscillator (OEO) with simultaneous broadband processing capabilities for both optical and electrical signals, while being readily implementable based on existing technologies. In this work, a new OEO-based RC (OEO-RC) using an electroabsorption modulated laser (EML) is designed, and the electroabsorption modulator (EAM) integrated in the EML serves as a nonlinear node. This scheme simplifies the architecture of an OEO-RC. And it is validated by using two typical tasks of the NARMA 10 time series prediction and the handwritten digit image recognition. Numerical results demonstrate that with optimized hyperparameters, this EML-based OEO-RC exhibits a comparable performance compared with some existing photonic time-delayed RCs. Full article

(This article belongs to the Special Issue Microwave Photonics: Advances and Applications)

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18 pages, 901 KB

Open AccessArticle

Node-Selective Cross-Layer Routing for Delay-Differentiated Services in Fine-Grained Optical Transport Networks

by Xin Du, Yuhui Wang, Yunxin Lv and Shuna Yang

Photonics 2026, 13(7), 645; https://doi.org/10.3390/photonics13070645 - 2 Jul 2026

Abstract

Fine-grained optical transport networks (fgOTNs) have attracted increasing interest in recent years for their ability to deliver small-granularity services with high flexibility and efficiency. To further improve the performance of fgOTNs in delivering small-granularity services having diverse delay requirements, this paper proposes and [...] Read more.

Fine-grained optical transport networks (fgOTNs) have attracted increasing interest in recent years for their ability to deliver small-granularity services with high flexibility and efficiency. To further improve the performance of fgOTNs in delivering small-granularity services having diverse delay requirements, this paper proposes and investigates a node-selective cross-layer service routing (NSCR) algorithm. By selecting a path based on both wavelength occupation and the quantity of currently active services that can be aggregated in the last optical hop, and by selecting proper intermediate nodes to participate in fgOTN layer exchange and aggregation under service delay constraints, the service blocking rate is reduced and resource utilization is maximized. Further, a variation of the proposed NSCR scheme is investigated that incorporates load balancing by selecting a path based on wavelength occupation, currently active service routes, and the remaining bandwidth. The performance of the two schemes is evaluated under both the NSFNET and Cost239 topologies, and the results demonstrate the superiority and effectiveness of the proposed schemes in terms of wavelength utilization rate and service blocking rate while satisfying the diverse delay requirements of different services. Full article

(This article belongs to the Special Issue Neural Networks in Optical Communications and Optical Computing: Implementation, Applications, and Prospects)

4 pages, 951 KB

Open AccessCorrection

Correction: Liu et al. Research on Distributed Temperature and Bending Sensing Measurement Based on DPP-BOTDA. Photonics 2025, 12, 1056

by Zijuan Liu, Yongqian Li and Lixin Zhang

Photonics 2026, 13(7), 644; https://doi.org/10.3390/photonics13070644 - 2 Jul 2026

Abstract

In the original publication [...] Full article

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32 pages, 6449 KB

Open AccessArticle

Quantum Origin of Circular Aperture Diffraction: A Velocity-Perpendicular Force Mechanism for Wave–Particle Interaction

by Chao-Fei Liu

Photonics 2026, 13(7), 643; https://doi.org/10.3390/photonics13070643 - 2 Jul 2026

Abstract

Starting from the circular aperture diffraction experiment, this paper decomposes the intrinsic interactions underlying wave–particle duality and proposes a specific interaction force: the velocity-perpendicular interaction force. We derive the characterization formula of this force and show that it can induce the phenomenon of [...] Read more.

Starting from the circular aperture diffraction experiment, this paper decomposes the intrinsic interactions underlying wave–particle duality and proposes a specific interaction force: the velocity-perpendicular interaction force. We derive the characterization formula of this force and show that it can induce the phenomenon of circular aperture diffraction of light, with the theoretical results being highly consistent with those calculated by the Huygens–Fresnel principle. The direction of this force is perpendicular to the relative velocity, originating from the coupling effect between the wave nature of light and the particle nature of the circular aperture structure, and it satisfies a modified inverse square law of distance related to the relative velocity. When photons pass through different positions of the circular aperture, the symmetry effect generates a net interaction time. The product of the main component of this force, the net interaction time, and the radius of the circular aperture constitutes a modulation quantity (a ratio of the Planck’s constant), which exerts an on–off modulation effect on the interaction force, thereby inducing the emergence of annular diffraction fringes. This study provides a novel physical interpretation for the circular aperture diffraction of light from the perspective of interaction forces and clarifies the possible existence form of wave–matter interaction forces. This force formula is expected to effectively describe the behavior of microscopic particles, just like the Schrödinger equation, while providing a brand-new perspective on interactions. It holds great application prospects in fields such as single-photon manipulation and quantum precision measurement. Full article

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26 pages, 37394 KB

Open AccessArticle

Process-Window Extended Laser Cleaning of Hot-Rolled Steel Oxide Scales: Based on Ablation and Thermal Vibration Synergy

by Hangcheng Zhang, Yuyang He, Yonghong Fu, Zehui Gu and Guodong Jia

Photonics 2026, 13(7), 642; https://doi.org/10.3390/photonics13070642 - 2 Jul 2026

Abstract

The efficient removal of tenacious oxide scales from hot-rolled steel surfaces represents a persistent challenge in advanced manufacturing, as traditional manual grinding methods exhibit poor efficiency and environmental compatibility. This investigation develops an innovative methodology, i.e., a “coarse-to-fine” hierarchical cleaning paradigm consisting of [...] Read more.

The efficient removal of tenacious oxide scales from hot-rolled steel surfaces represents a persistent challenge in advanced manufacturing, as traditional manual grinding methods exhibit poor efficiency and environmental compatibility. This investigation develops an innovative methodology, i.e., a “coarse-to-fine” hierarchical cleaning paradigm consisting of dual-stepwise laser cleaning with variable parameters that successfully addresses the restrictive process window inherent to conventional single-parameter techniques. Through a strategically designed sequential treatment protocol—employing initial low-frequency (20 kHz), high-energy-density (200 mm/s) laser irradiation for primary oxide ablation, succeeded by high-frequency (60 kHz), low-energy-density (4000 mm/s) processing for residual scale elimination—we demonstrate an optimal synergy between ablative and thermomechanical vibration mechanisms. Rigorous multi-modal characterization incorporating SEM-EDS microscopy, oxygen content quantification, and metallographic analysis confirms exceptional performance metrics, including 98.7% oxide removal efficiency and 43.2% reduction in substrate surface roughness relative to standard methods. The developed protocol achieves a 2.8-fold expansion of the operational parameter space while establishing a novel “coarse-to-fine” hierarchical cleaning paradigm. These findings offer fundamental insights into laser–matter interactions while delivering a transferable technological framework for high-value manufacturing sectors, particularly in automotive and aerospace component production. Full article

(This article belongs to the Special Issue Advanced and Efficient Non-Destructive Laser Cleaning)

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15 pages, 2464 KB

Open AccessArticle

Optical Mask Generation Based on State-Switching Dynamics for Time-Delay Reservoir Computing

by Tong Zhao, Tianpei Cui, Baofeng Feng, Zhimin Bai, Pengfa Chang, Lijun Qiao, Su Yan and Xiaopeng Fan

Photonics 2026, 13(7), 641; https://doi.org/10.3390/photonics13070641 - 1 Jul 2026

Abstract

In time-delay reservoir computing (TDRC), mask signal generation techniques in the input layer remain a key factor limiting system integration. In this study, we propose an optical mask generation scheme based on steady–quasi-periodic state switching (S-QPS) dynamics in a semiconductor laser with optical [...] Read more.

In time-delay reservoir computing (TDRC), mask signal generation techniques in the input layer remain a key factor limiting system integration. In this study, we propose an optical mask generation scheme based on steady–quasi-periodic state switching (S-QPS) dynamics in a semiconductor laser with optical feedback. Experimentally generated S-QPS signals are applied to a TDRC system as mask signals, and the system performance is evaluated using the Santa Fe chaotic time-series prediction task. S-QPS signals are numerically generated based on the Lang–Kobayashi rate equations. The optimal normalized mean square error is 0.027. An analysis of the factors affecting system performance is carried out. The results indicate that period offset has a limited impact on system performance. In contrast, noise-induced amplitude fluctuations have a more pronounced impact. These results provide insights into the use and optimization of S-QPS signals for optical mask generation in TDRC systems. Full article

(This article belongs to the Special Issue Advanced Lasers and Their Applications, 3rd Edition)

12 pages, 2323 KB

Open AccessArticle

Symmetric 100 Gb/s CO-OFDM-PON with Massive Connectivity for Ultra-Dense Industrial Access Networks

by Zhanglu Zhao, Zhengxuan Li, Pengyu Zhang, Jiahao Huo, Siyu Luo, Chenyu Liu, Mingyang Shao, Yingxiong Song and Lilin Yi

Photonics 2026, 13(7), 640; https://doi.org/10.3390/photonics13070640 - 1 Jul 2026

Abstract

Industrial automation and the Internet of Things (IoT) are driving demand for optical access networks capable of supporting massive connectivity with deterministic low latency. Conventional passive optical networks (PONs) face scalability and cost limitations in ultra-dense deployment scenarios. Here we propose and experimentally [...] Read more.

Industrial automation and the Internet of Things (IoT) are driving demand for optical access networks capable of supporting massive connectivity with deterministic low latency. Conventional passive optical networks (PONs) face scalability and cost limitations in ultra-dense deployment scenarios. Here we propose and experimentally demonstrate a polarization-carrier dual-reuse coherent orthogonal frequency division multiplexing PON (CO-OFDM-PON) architecture enabled by optical frequency comb (OFC) sources. The design maps data and carrier signals onto orthogonal polarization states. This enables carrier reuse for both downstream coherent detection and upstream transmission through injection-locked laser (ILL)-based carrier regeneration at the optical network unit (ONU). We comprehensively characterize the key subsystems. These include the OFC, ILL, and erbium-doped fiber amplifier (EDFA). This ensures stable multi-wavelength generation, carrier regeneration, and enhanced receiver sensitivity under high split ratios. Through simulation and experimental analysis of fiber nonlinearities in industrial PON scenarios, we identify an optimal per-channel launch power of 4 dBm. This power balances sensitivity and link budget requirements. Scalability analysis for standard PON reach is also provided. The system demonstrates 16-channel 100 Gb/s per wavelength downstream 16-QAM OFDM transmission. The link budget exceeds 34 dB with bit error rates (BERs) below the forward error correction (FEC) threshold of 1 × 10⁻². While the coherent ONU architecture offers superior spectral efficiency, it entails higher component costs than direct-detection alternatives due to the required coherent receiver and polarization management components. Full article

(This article belongs to the Special Issue Optical Communication Networks: Challenges and Opportunities)

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10 pages, 12861 KB

Open AccessArticle

Broadband Optical Edge Detection Based on Two-Dimensional Liquid Crystal Polarization Grating

by Ying Ma, Zhen Yang, Haonan Li, Xiangyu Li and Yuhang Shan

Photonics 2026, 13(7), 639; https://doi.org/10.3390/photonics13070639 - 1 Jul 2026

Abstract

A two-dimensional liquid crystal polarization grating (2D-LCPG) is realized by using a single-exposure photoalignment system. When using a horizontal polarized light as the reference incident light, four circular polarized light beams are captured with a 4f system to realize image extraction and [...] Read more.

A two-dimensional liquid crystal polarization grating (2D-LCPG) is realized by using a single-exposure photoalignment system. When using a horizontal polarized light as the reference incident light, four circular polarized light beams are captured with a 4f system to realize image extraction and detection. Compared with a 1D-LCPG, the experimental results demonstrate better integrity and accuracy in extracting edge information with the proposed 2D-LCPG. Broadband edge detection capability was tested under visible wavelength range. Results show good edge detection even without an electric field. The resolutions are up to 15.63 µm for incident light of 633 nm, 532 nm by applying a 0.3 V/µm electric field, and 450 nm by applying a 0.5 V/µm electric field. With these advantages, optical edge detection based on the proposed 2D-LCPG could have potential applications in image processing, remote sensing, and other related areas. Full article

(This article belongs to the Special Issue Latest Advances in Optical Diffraction, Imaging and Display)

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12 pages, 1561 KB

Open AccessArticle

Nondestructive Detection of Thermal Aging in XLPE Based on Terahertz Spectroscopy

by Junping Cao, Wenhui Yan, Yiming Zheng, Jiayu Liu, Zhiyi Gao, Baiqiang Sun, Yuntu Jiang, Yu Ma and Zhenwei Zhang

Photonics 2026, 13(7), 638; https://doi.org/10.3390/photonics13070638 - 1 Jul 2026

Abstract

XLPE power cables have become the core insulation material in the power cable industry and are widely used in high-voltage and extra-high-voltage cable systems due to their advantages of large transmission capacity, excellent dielectric properties, and stable physicochemical characteristics. The aging state of [...] Read more.

XLPE power cables have become the core insulation material in the power cable industry and are widely used in high-voltage and extra-high-voltage cable systems due to their advantages of large transmission capacity, excellent dielectric properties, and stable physicochemical characteristics. The aging state of XLPE directly affects the safety and stability of power transmission. Therefore, an in-depth analysis of the aging mechanisms, a thorough understanding of the aging patterns, and the establishment of a scientific aging condition assessment framework are of great significance for ensuring the reliable operation of XLPE cables. In this paper, a nondestructive detection study of thermal aging in XLPE is conducted based on terahertz (THz) spectroscopy, focusing on the evolution of optical parameters during the thermal aging process. The research demonstrates that THz spectroscopy can sensitively capture the dynamic changes occurring during the thermal aging of XLPE. This provides a novel technical approach and theoretical support for the nondestructive evaluation of thermal aging in the cable industry. The findings hold substantial theoretical value and practical significance for safeguarding the secure and reliable operation of power cables and preventing electrical accidents. Full article

(This article belongs to the Section New Applications Enabled by Photonics Technologies and Systems)

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26 pages, 2694 KB

Open AccessArticle

Optimization of a LaF-Coupled Au/BaTiO₃/WS₂ SPR Sensor for Multi-Ion Heavy Metal Monitoring in Water: A Numerical Study

by Talia Tene, Malika Doghmane, Fredy Daniel Romero Herrera, Jessica Alexandra Marcatoma Tixi, Elfahem Sakher, Nozha El Ahlem Doghmane, Lala Gahramanli and Cristian Vacacela Gomez

Photonics 2026, 13(7), 637; https://doi.org/10.3390/photonics13070637 - 1 Jul 2026

Abstract

Introduction: Heavy metal contamination in water represents a major environmental and public health challenge because toxic ions frequently occur as complex multi-species mixtures rather than isolated pollutants. This study presents a numerical design and optimization of a surface plasmon resonance (SPR) sensor based [...] Read more.

Introduction: Heavy metal contamination in water represents a major environmental and public health challenge because toxic ions frequently occur as complex multi-species mixtures rather than isolated pollutants. This study presents a numerical design and optimization of a surface plasmon resonance (SPR) sensor based on a LaF/Au/BaTiO₃/WS₂ heterostructure for monitoring refractive-index changes associated with mixed heavy metal ions in aqueous media. Methodology: The optical response of the multilayer sensor was evaluated using the transfer matrix method under TM-polarized illumination at 633 nm. Systematic optimization was performed for the prism substrate, Au thickness, dielectric oxide layer, and 2D nanomaterial interface. The final configuration consisted of a LaF prism, 50 nm Au film, 2.0 nm BaTiO₃ spacer, and 0.80 nm WS₂ monolayer. Sensor performance was assessed using resonance-angle shift, sensitivity, detection accuracy, quality factor, figure of merit, FWHM, attenuation, and estimated limit of detection. Results and Discussion: The optimized LaF/Au/BaTiO₃/WS₂ configuration produced stable simulated SPR responses across single, binary, quaternary, and five-ion heavy metal matrices. The WS₂ monolayer provided the highest angular displacement among the evaluated 2D materials, while BaTiO₃ improved field confinement and limited optical damping in the numerical model. The configuration maintained attenuation near 1.6%, FWHM values around 7.9°, detection accuracy between 0.030 and 0.032 deg⁻¹, and model-based refractometric LoD values down to 3.49 × 10⁻⁵ RIU under the assumed angular-resolution criterion. Conclusions: The proposed LaF/Au/BaTiO₃/WS₂ SPR configuration provides a numerical framework for label-free monitoring of refractive-index changes associated with complex heavy-metal-ion mixtures in contaminated water. Experimental fabrication and testing are required to validate the simulated performance. Full article

(This article belongs to the Special Issue Low-Dimensional Materials for Optoelectronic and Photonic Fundamentals and Applications)

13 pages, 6092 KB

Open AccessArticle

Effects of Substituted Tryptamines on the Excitonic Structure of the Tubulin Tryptophan Network

by Matthew T. Colbourne, Lea Gassab and Travis J. A. Craddock

Photonics 2026, 13(7), 636; https://doi.org/10.3390/photonics13070636 - 30 Jun 2026

Abstract

Microtubules contain ordered aromatic amino acid networks whose optical excitations have been proposed to support non-trivial energy-transfer dynamics. Here, we examined whether bound tryptamine ligands can perturb the excitonic structure of the tubulin tryptophan network. A virtual screen of 294 tryptamines was performed [...] Read more.

Microtubules contain ordered aromatic amino acid networks whose optical excitations have been proposed to support non-trivial energy-transfer dynamics. Here, we examined whether bound tryptamine ligands can perturb the excitonic structure of the tubulin tryptophan network. A virtual screen of 294 tryptamines was performed across seven known binding regions of the tubulin heterodimer using AutoDock Vina 1.2.6. From this screen, top-ranked tryptamine ligands were carried forward for excited-state analysis. Geometry optimization and time-dependent density functional theory (TD-DFT) calculations were used to obtain vertical excitation energies and transition dipole moments for the ligand-bound states in the ultraviolet range. These ligand properties were then incorporated into a tight-binding Hamiltonian describing the tubulin tryptophan excitation network in order to evaluate changes in exciton energies and eigenvector delocalization. The calculations indicate that tryptamine binding can modify the excitonic landscape of tubulin in a ligand-dependent manner, with the magnitude of the perturbation governed by excitation wavelength, transition dipole strength, and spatial orientation relative to the intrinsic tryptophan network. These results show that substituted tryptamines differ in how they perturb the modeled tubulin tryptophan excitonic manifold, but they do not by themselves establish experimentally resolvable modulation of tubulin or microtubule photophysics. The present work should therefore be interpreted as a first-pass computational screening framework for prioritizing ligands and defining future experimental tests. Full article

(This article belongs to the Section Biophotonics and Biomedical Optics)

21 pages, 3987 KB

Open AccessReview

Review of Nanoscale Precision Shape and Property Control Manufacturing Technology for Monocrystalline Silicon

by Shuo Qiao, Zizhang Wang, Zhangfu Huang, Bo Zhang and Xiaoshu Xu

Photonics 2026, 13(7), 635; https://doi.org/10.3390/photonics13070635 - 30 Jun 2026

Abstract

Monocrystalline silicon, with its high refractive index, high infrared transmittance, and excellent dimensional stability, serves as a key optical component in high-energy laser systems, infrared imaging, and guidance fields. Its processing quality directly affects the performance indicators of related systems. To address the [...] Read more.

Monocrystalline silicon, with its high refractive index, high infrared transmittance, and excellent dimensional stability, serves as a key optical component in high-energy laser systems, infrared imaging, and guidance fields. Its processing quality directly affects the performance indicators of related systems. To address the challenges of nanoscale precision shape and property control during processing, methods such as ultra-precision cutting, magnetorheological polishing, laser micromachining, ion beam processing, plasma etching, and chemical–mechanical polishing have been adopted to improve the surface shape accuracy and repair defects of monocrystalline silicon components. This paper reviews the research progress of key technologies, including nanoscale precision surface shape control manufacturing technology, nanoscale precision property control generation methods, and combined processes for its nanoscale shape and property control, providing technical support for achieving nanoscale precision shape and property control manufacturing of monocrystalline silicon components. Full article

(This article belongs to the Special Issue Advances in Micro-Nano Optical Manufacturing)

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10 pages, 2029 KB

Open AccessArticle

On-Chip THz Mach–Zehnder Interferometer Integrated with Polarization Splitter and Rotator for Biomedical Applications

by Zhehao Yan, Yipeng Lu, Qunzhen Peng, Tong Zhai and Guocheng Ding

Photonics 2026, 13(7), 634; https://doi.org/10.3390/photonics13070634 - 30 Jun 2026

Abstract

We propose a novel silicon-based THz Mach–Zehnder interferometer (MZI) biosensor integrated with a polarization splitter and rotator (PSR). An optimized PSR is positioned at the input of the MZI, enabling arbitrary polarization inputs to be converted into the same TE mode, which eliminates [...] Read more.

We propose a novel silicon-based THz Mach–Zehnder interferometer (MZI) biosensor integrated with a polarization splitter and rotator (PSR). An optimized PSR is positioned at the input of the MZI, enabling arbitrary polarization inputs to be converted into the same TE mode, which eliminates the dependence of conventional MZI sensors on the input light polarization. The PSR structural parameters are optimized using 3D-FDTD simulations to achieve phase matching, and the calculation results show that efficient TM–TE-polarization conversion occurs along a coupling length of 22.9 mm. Furthermore, the PSR achieves a maximum TE-mode extinction ratio of −30.1 dB and a polarization conversion efficiency of 82.33% in the 0.44 to 0.45 THz range, effectively maintaining the polarization consistency of light entering the MZI. Meanwhile, the characteristic frequency shows a regular blue shift with increasing external refractive index, and the final results demonstrate that the designed MZI biosensor achieves a high sensitivity of 13,215.81 nm/RIU near the center frequency of 0.45 THz. All results presented in this work are obtained through numerical simulations, and experimental validation as well as analyte-concentration-dependent refractive index characterization will be addressed in future studies. To sum up, we propose a high-sensitivity terahertz MZI biosensor featuring a PSR with an on-chip integration scheme, which supports arbitrary polarization inputs and offers a highly integrated solution for specific detection in biomedicine. Full article

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