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A Two-Point Propagation Field of a Single Photon: A Way to X-Ray Picometer Displacement Detection and Nanometer Resolution 3D X-Ray Micro-Tomography
X-UV Radiative Processes in Structurally Active Media
Algebraic Absorption in Non-Hermitian Photonic Lattices
Fiber Bragg Grating Accelerometers: A Review from Single-Axis to Multi-Dimensional Vector Sensing

Journal Description

Photonics

Photonics is an international, scientific, peer-reviewed, open access journal on the science and technology of optics and photonics, published monthly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, Ei Compendex, CAPlus / SciFinder, and other databases.
Journal Rank: CiteScore - Q2 (Instrumentation)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 13.9 days after submission; acceptance to publication is undertaken in 2.6 days (median values for papers published in this journal in the first half of 2026).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Companion journals for Photonics include: Lights, Lasers and Optoelectronics.
Journal Cluster of Atomic, Molecular, and Optical (AMO) Physics: Entropy, Photonics, Atoms, Lights, Optics, Physics and Quantum Beam Science.

Impact Factor: 2.1 (2025); 5-Year Impact Factor: 2.1 (2025)

Imprint Information Journal Flyer Open Access ISSN: 2304-6732

Latest Articles

27 pages, 3972 KB

Open AccessReview

AI-Driven Photonic Front-Ends for 6G Visible Light Communication: From Micro-LEDs and Reconfigurable Optics to Energy-Autonomous Receivers

by Amjad Ali, Syed Raza Mehdi, Shulan Lin, Ying Xu, Pablo Palacios Jativa, Waseem Ur Rahman, Baseerat Bibi, Ameen Alkasem, Mehboob Hussain and Zeeshan Shafiq

Photonics 2026, 13(8), 779; https://doi.org/10.3390/photonics13080779 - 17 Aug 2026

Visible light communication (VLC) has emerged as a transformative optical wireless technology for sixth-generation (6G) networks, offering license-free spectrum access, inherent electromagnetic-interference immunity, high spatial confinement, and the unique ability to combine high-speed wireless connectivity with solid-state lighting infrastructure. However, the transition from [...] Read more.

Visible light communication (VLC) has emerged as a transformative optical wireless technology for sixth-generation (6G) networks, offering license-free spectrum access, inherent electromagnetic-interference immunity, high spatial confinement, and the unique ability to combine high-speed wireless connectivity with solid-state lighting infrastructure. However, the transition from conventional VLC links to practical 6G optical wireless systems requires far more than advanced modulation and signal processing. Future VLC performance will be strongly determined by the co-design of photonic front-ends, including high-speed transmitters, spectrally engineered emitters, reconfigurable optical interfaces, intelligent receivers, and energy-autonomous detection units. This article provides a comprehensive, device-centered review of photonic hardware and artificial intelligence (AI) enablers for next-generation 6G VLC systems. Particular attention is given to micro-LEDs, laser diodes, color-conversion materials, including perovskite quantum dots, advanced photodetectors, imaging receivers, wavelength-shifting fiber receivers, solar-cell-based receivers, optical reconfigurable intelligent surfaces (RISs), metasurfaces, beam-steering components, and optical wireless power transfer. This review discusses how AI can support inverse photonic design, transmitter and receiver calibration, nonlinear impairment mitigation, channel-aware beam control, and energy-aware resource management. Unlike broader VLC surveys that mainly emphasize network architecture, this article provides a device-centered perspective on AI-enabled photonic integration for 6G VLC, supported by a comprehensive survey of recent experimental demonstrations. Key challenges related to bandwidth, optical efficiency, receiver field of view, mobility, safety, standardization, and practical deployment are summarized, followed by a research roadmap for 2025–2032. Full article

(This article belongs to the Special Issue Next-Generation VLC Systems for 6G: AI-Enabled Design and Photonic Integration)

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11 pages, 1529 KB

Open AccessArticle

Trust Region Bayesian Optimization (TuRBO) for High-Saturation Structural Red Based on Sb₂S₃ Metasurfaces

by Yunhan Wu, Bo Ni and Lifu Wu

Photonics 2026, 13(8), 778; https://doi.org/10.3390/photonics13080778 - 17 Aug 2026

Highly saturated structural colors are crucial for the micro-nanophotonic displays. However, achieving Schrödinger’s red pixels remains a challenge due to the difficulty in suppressing higher-order resonances in the blue-green wavelength band. In this paper, we utilize the TuRBO algorithm for global physical parameter [...] Read more.

Highly saturated structural colors are crucial for the micro-nanophotonic displays. However, achieving Schrödinger’s red pixels remains a challenge due to the difficulty in suppressing higher-order resonances in the blue-green wavelength band. In this paper, we utilize the TuRBO algorithm for global physical parameter optimization of periodic

{Sb}_{2} S_{3}

nanopillar metasurface structures to realize the high-saturation red. Based on the intrinsic dispersion characteristics of

{Sb}_{2} S_{3}

characterized by high extinction coefficients in the blue-green wavelength band, the high-saturation Schrödinger’s red that surpasses the Adobe RGB boundary has been produced successfully. The calculated results show that after 45 iterations, the structure achieves gradient refractive index matching, aligning the intrinsic dispersion of

{Sb}_{2} S_{3}

with the ideal reflection spectrum of Schrödinger’s red pixels, thereby effectively suppressing higher-order resonances in the blue-green wavelength band. Ultimately, an ultra-high saturation red is achieved with CIE coordinates of (0.6507, 0.3043) in the CIE chromaticity space. Full article

(This article belongs to the Special Issue AI for Photonics: Intelligent Imaging, Learning-Driven Optics, and Photonic Computing)

29 pages, 9590 KB

Open AccessArticle

SCVolFormer: Spectral Consistency–Guided Volumetric Linear Self–Attention Transformer for Hyperspectral Unmixing

by Xinyu Cui, Xinyue Zhang, Da Sun and Aoran Dai

Photonics 2026, 13(8), 777; https://doi.org/10.3390/photonics13080777 - 17 Aug 2026

Hyperspectral unmixing (HU) requires effective modeling of spectral–spatial information and local–global feature interactions to achieve accurate abundance estimation and endmember extraction. Although Transformer-based HU methods are effective in capturing long-range dependencies, they often neglect the intrinsic spectral consistency of hyperspectral data and do [...] Read more.

Hyperspectral unmixing (HU) requires effective modeling of spectral–spatial information and local–global feature interactions to achieve accurate abundance estimation and endmember extraction. Although Transformer-based HU methods are effective in capturing long-range dependencies, they often neglect the intrinsic spectral consistency of hyperspectral data and do not fully exploit the global spectral–spatial correlations in hyperspectral image cubes. To address these issues, this paper proposes a Spectral Consistency–guided Transformer with Volumetric Linear Self-Attention (SCVolFormer) for hyperspectral unmixing. A Spectral Consistency Block (SCB) is introduced to preserve consistency across adjacent spectral bands and produce physically meaningful feature representations. A spectral grouping strategy is further adopted to partition the high-dimensional spectrum into locally continuous subspaces, reducing computational cost. In addition, a shared-weight Transformer encoder with Volumetric Linear Self-Attention (VolLSA) is designed to model interactions between the spectral and spatial dimensions and capture long-range dependencies within hyperspectral image cubes. A decoder is then used to estimate abundance maps and reconstruct hyperspectral images. Experiments on one synthetic dataset and three real hyperspectral datasets demonstrate that SCVolFormer outperforms state-of-the-art methods in abundance estimation and endmember extraction, confirming the effectiveness of spectral consistency guidance and volumetric attention modeling for hyperspectral unmixing. Full article

(This article belongs to the Special Issue Advances in Spectroscopic Imaging: Science and Technology)

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17 pages, 2106 KB

Open AccessArticle

Uncertainty-Aware C-Band Launch-Power Profile Selection with GNPy: A Reproducible Tail-Risk Study

by Yuxin Xia and Zhiguang Li

Photonics 2026, 13(8), 776; https://doi.org/10.3390/photonics13080776 - 17 Aug 2026

Nominal launch-power profiles can lose quality-of-transmission (QoT) margin when span and equipment parameters vary. We study this effect using C-band GNPy 2.14.1 simulations that recompute amplified-spontaneous-emission (ASE) noise and Gaussian-noise (GN)-model nonlinear interference under perturbations. Ten runs use 384 training scenarios and 1024 [...] Read more.

Nominal launch-power profiles can lose quality-of-transmission (QoT) margin when span and equipment parameters vary. We study this effect using C-band GNPy 2.14.1 simulations that recompute amplified-spontaneous-emission (ASE) noise and Gaussian-noise (GN)-model nonlinear interference under perturbations. Ten runs use 384 training scenarios and 1024 intensified-stress scenarios with scalar and spectral multipliers of 1.25 and 1.50. In paired within-GNPy comparisons, a finite-sample 5% lower-tail-mean selector, defined as the mean of the 20 worst training utilities, improves fifth-percentile minimum-channel generalized signal-to-noise-ratio (GSNR) margin over nominal optimization by 0.247 dB, with a 95% confidence-interval half-width of 0.014 dB. After normalization to the nominal total launch power, the gain remains 0.179 dB (half-width 0.017 dB), suggesting that spectral shape is a major contributor to the paired difference in this comparison. The gain lies between 0.245 and 0.248 dB when the training-tail fraction varies from 1% to 10%; relaxing the per-channel ceiling from 3.0 to 3.5 dBm removes almost all active bounds while retaining a 0.246 dB gain. Selected profiles mainly raise the low-frequency edge, and the benefit appears near the modeled reach boundary rather than on high-margin metro links. Erbium-doped fiber amplifier noise figure, gain ripple, and reconfigurable optical add-drop multiplexer equalization lead the sensitivity ranking. Reduced Manakov checks preserve power ordering while exposing model offsets. The results describe the specified GNPy configuration, finite search, and synthetic perturbation laws; field-calibrated performance remains to be established. Full article

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16 pages, 4622 KB

Open AccessArticle

Observation of Rabi-like Oscillation in a Microwave Photonic-Based Two-Level System

by Zhuoshen Shi, Sheng Dong, Yicheng Huang, Junqi Wang, Jiakang Shi, Jianghai Wo, Xudong Wang, Jiejun Zhang and Jianping Yao

Photonics 2026, 13(8), 775; https://doi.org/10.3390/photonics13080775 - 17 Aug 2026

Discrete energy-level dynamics provide a fundamental framework for understanding driven two-state systems. Here, we propose and experimentally demonstrate a classical microwave-photonic analog based on two active fiber loops. Reciprocal electro-optic sidebands coherently couple two independently sustained lasing modes. When the input RF power [...] Read more.

Discrete energy-level dynamics provide a fundamental framework for understanding driven two-state systems. Here, we propose and experimentally demonstrate a classical microwave-photonic analog based on two active fiber loops. Reciprocal electro-optic sidebands coherently couple two independently sustained lasing modes. When the input RF power is increased from 11.7 to 18.7 dBm, the measured oscillation frequency increases from 0.55 to 1.00 MHz, consistent with the modulation-induced coupling predicted by the coupled-mode model. The experiment therefore demonstrates RF-power-controlled Rabi-like oscillation in an active dual-loop system. Because the optical fields and detected intensities are classical, the platform reproduces reduced two-state dynamics rather than quantum-state evolution. This proof-of-concept provides a basis for quantum-inspired microwave-photonic signal processing and future short-cavity implementations. Full article

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16 pages, 4601 KB

Open AccessArticle

Refractive–Metalens Hybrid Design for Cooled MWIR Imaging System

by Junsong Wang, Mingxu Piao, Xian Zhang, Keyan Dong, Zhongju Ren and Huilin Jiang

Photonics 2026, 13(8), 774; https://doi.org/10.3390/photonics13080774 - 16 Aug 2026

Conventional cooled infrared optical systems employ a cold stop, which disrupts optical-path symmetry and constrains exit-pupil matching. Consequently, reducing the refractive lens count increases the residual broadband-aberration burden, motivating the introduction of an ultrathin phase-compensation element near the exit pupil. Conventional solutions therefore [...] Read more.

Conventional cooled infrared optical systems employ a cold stop, which disrupts optical-path symmetry and constrains exit-pupil matching. Consequently, reducing the refractive lens count increases the residual broadband-aberration burden, motivating the introduction of an ultrathin phase-compensation element near the exit pupil. Conventional solutions therefore tend to use complex optical configurations with large volume and high weight, making it challenging to meet the demands of modern lightweight and compact detection systems. Metalenses offer a new approach for aberration correction through the flexible phase manipulation enabled by their unit cells. However, severe chromatic dispersion of metalenses under broadband conditions remains a major obstacle to their practical application. To address this issue, a hybrid refractive–metalens design method for cooled infrared optical systems is proposed. Based on the distinctive phase distribution characteristics of metalenses, an achromatic theoretical formulation applicable to broadband infrared wavelengths is derived. Guided by this theory, a cooled mid-wave infrared refractive–metalens hybrid optical system is designed, featuring a full field of view of 126°, an F-number of 2, and an operating wavelength band of 3.3–5 μm. In comparison with a conventional eight-element refractive system of identical specifications, the proposed hybrid system reduces the total optical-element count from eight to four and achieves reductions of 21% in total track length and 79% in system weight, while maintaining a full-field polychromatic MTF above 0.4 at 33 lp/mm. In addition, the narcissus effect is effectively mitigated under the modeled conditions. This approach enables high-performance aberration correction using metalenses while offering a new design paradigm for simplified infrared optical systems. Full article

(This article belongs to the Special Issue Advanced Optoelectronic Systems)

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18 pages, 2514 KB

Open AccessArticle

Meta-Learning-Driven Photon Counting Multi-User Satellite Communications over Strong Atmospheric Turbulence Channels

by Yuelai Chen, Ruoshi Gu, Aleksandra Panajotović, Jun Zhang, Jun Huang, Liang Zhang and Xiaolin Zhou

Photonics 2026, 13(8), 773; https://doi.org/10.3390/photonics13080773 - 16 Aug 2026

Photon-counting constitute a promising technology for ultra-weak signal satellite communications. Considering the Poisson shot noise impairment, atmospheric turbulence fading, and multi-user interference, in this paper, a meta-learning-driven photon-counting multi-user single-input multiple-output (MU-SIMO) scheme is developed and analyzed. Referred to as meta-learning-driven signal detection [...] Read more.

Photon-counting constitute a promising technology for ultra-weak signal satellite communications. Considering the Poisson shot noise impairment, atmospheric turbulence fading, and multi-user interference, in this paper, a meta-learning-driven photon-counting multi-user single-input multiple-output (MU-SIMO) scheme is developed and analyzed. Referred to as meta-learning-driven signal detection (Meta-SD), this scheme can achieve rapid convergence with limited samples and significantly improve system detection performance. Simulation results demonstrate that the proposed meta-learning scheme outperforms the mean square error based signal detection (MSE-SD) baseline, in terms of detection accuracy, robustness to signal-dependent Poisson shot noise, convergence speed, and generalization to few-shot detection tasks with previously untrained signal classes. Specifically, Meta-SD achieves nearly a tenfold reduction in BER, compared with the derived MSE-SD benchmark, in a

4 \times 8

MU-SIMO scenario at

E_{s} = - 140

dBJ. Full article

(This article belongs to the Special Issue New Advances in Optical Wireless Communication, 2nd Edition)

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27 pages, 2215 KB

Open AccessArticle

Remodulation-Based Bidirectional FSO Transceiver Module Integrating a Fluorescent-Concentrator and a Modulating Retroreflector

by Jiyeon Baek, Yuna Lee and Hyunchae Chun

Photonics 2026, 13(8), 772; https://doi.org/10.3390/photonics13080772 - 16 Aug 2026

Compact mobile optical wireless communication (OWC) terminals are constrained not only by link budget but also by mobile-side size, weight, power consumption, and cost (SWaP-C). This paper proposes and models a remodulation-based bidirectional OWC transceiver module that integrates a fluorescent concentrator (FC) receiver [...] Read more.

Compact mobile optical wireless communication (OWC) terminals are constrained not only by link budget but also by mobile-side size, weight, power consumption, and cost (SWaP-C). This paper proposes and models a remodulation-based bidirectional OWC transceiver module that integrates a fluorescent concentrator (FC) receiver and a modulating retroreflector (MRR) transmitter. The FC receives the downlink by absorbing a wavelength-dependent fraction of an interrogation beam, Stokes-shifting the absorbed light, and guiding the emission to an edge photodetector. The transmitted fraction of the same interrogation beam reaches the MRR and is remodulated for low-power uplink transmission without a mobile-side optical source. The central design variable is therefore not the optical power alone, but the pair consisting of the interrogation wavelength and the downlink modulation depth. A fully absorbed wavelength with high modulation depth is used for downlink-only operation, a pass-through wavelength with zero modulation depth is used for uplink-only operation, and an absorption-shoulder wavelength with intermediate modulation depth is used for simultaneous downlink and uplink remodulation. A spectral photon-transfer model, a direct-detection communication model, a self-interference model, and a weighted rate-optimization framework are developed. Simulation results show that the optimized wavelength shifts from the FC absorption peak in downlink-dominant operation to the FC pass-through window in uplink-dominant operation, while the optimal downlink modulation depth decreases to preserve uplink carrier margin. The proposed architecture is particularly well-suited for drones, robots, vehicles, and distributed sensors requiring robust optical downlink reception and low-SWaP-C uplink signaling. Full article

(This article belongs to the Special Issue Machine Learning and Artificial Intelligence for Optical Networks)

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15 pages, 13343 KB

Open AccessArticle

High-Stability Actively Mode-Locked Fiber Lasers Based on DFB-LD Injection Locking with F-P Frequency Stabilization

by Ju Wang, Manyun Liu, Hao Luo, Xingmiao Li, Xuemin Su, Chuang Ma and Jinlong Yu

Photonics 2026, 13(8), 771; https://doi.org/10.3390/photonics13080771 - 15 Aug 2026

A high-stability actively mode-locked fiber laser (AMLFL) is proposed and experimentally demonstrated. This AMLFL is based on a distributed feedback laser diode (DFB-LD) injection locking with Fabry-Perot (F-P) etalon frequency stabilization. In this system, a wavelength modulation method is employed to generate the [...] Read more.

A high-stability actively mode-locked fiber laser (AMLFL) is proposed and experimentally demonstrated. This AMLFL is based on a distributed feedback laser diode (DFB-LD) injection locking with Fabry-Perot (F-P) etalon frequency stabilization. In this system, a wavelength modulation method is employed to generate the feedback signal for frequency stabilization. The stabilization mechanism utilizes the linear response characteristic of the first-order derivative of the F-P etalon transmission peak. This achieves wavelength stabilization of the DFB-LD. Subsequently, the stabilized light source is injected into the ring cavity of the AMLFL. The proposed system does not require modification to the existing AMLFL cavity. It also features a simple structure and low implementation cost. Experimental results show that, with frequency stabilization, the wavelength drift of a selected spectral line is reduced to within the 10 pm resolution of the OSA. Meanwhile, the standard deviations of the 5 GHz spectral component power fluctuation and the average output optical pulse power are 0.01 dB and 0.01 dB, respectively. Full article

(This article belongs to the Special Issue Lasers and Complex System Dynamics)

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23 pages, 27998 KB

Open AccessArticle

Dual-Rotary Trepanning of High-Quality Film Cooling Holes in DD6 Superalloy Using a Nanosecond Fiber Laser

by Shichao Chang, Mengqi Suo, Chaowei Sun, Anbo Hu, Kang Li, Jichao Yang, Danyi Zhang, Fazhan Tao, Tianqing Jia and Hongxing Xu

Photonics 2026, 13(8), 770; https://doi.org/10.3390/photonics13080770 - 15 Aug 2026

High-quality and high-efficiency machining of film cooling holes (FCHs) is critical for enhancing the performance of gas turbines and aero-engines. Nanosecond fiber lasers offer advantages such as high stability, good beam quality, and ease of integration. However, when machining FCHs, issues including low [...] Read more.

High-quality and high-efficiency machining of film cooling holes (FCHs) is critical for enhancing the performance of gas turbines and aero-engines. Nanosecond fiber lasers offer advantages such as high stability, good beam quality, and ease of integration. However, when machining FCHs, issues including low drilling efficiency and significant thermal effects severely limit their industrial applications. In this study, a dual-rotary trepanning system was developed based on a nanosecond fiber laser, a galvanometer, and a five-axis cradle machine. High-quality FCHs with a diameter of 0.6 mm were efficiently machined in a 3-mm-thick DD6 superalloy plate within only 6.5 s. Compared with the method using machine tool rotation alone, the average recast layer thickness on the inner wall was reduced by 62.1% to 6.7 μm, and the average surface roughness was reduced by 61.1% to 0.35 μm. These improvements are primarily attributed to the galvanometer speed being two orders of magnitude higher than that of the machine tool, which significantly reduces the laser pulse overlap rate and the thermal accumulation effect. Moreover, the kerf widened by the galvanometer rotation allows the ablation products to expand more fully and be expelled efficiently, thereby reducing impact, scratching, and debris adhesion on the inner wall and improving the drilling efficiency. Furthermore, 10 × 10 FCH arrays were machined on both vertical and inclined plates, demonstrating high consistency and stability, indicating the potential for industrial applications in the field of FCH machining. Full article

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13 pages, 6030 KB

Open AccessArticle

Femtosecond Laser Machining of Irregularly Shaped Film Cooling Holes: The Influence of Defocus Distance

by Zhen Wang, Junjie Xu, Lifei Wang and Zhen Zhang

Photonics 2026, 13(8), 769; https://doi.org/10.3390/photonics13080769 - 15 Aug 2026

Film cooling holes are critical cooling structures that enhance the temperature-bearing capacity of turbine blades. Irregularly shaped holes, such as laidback fan-shaped holes (LFSHs), have been demonstrated to exhibit superior cooling performance compared to traditional circular holes. However, the complex shapes and structures [...] Read more.

Film cooling holes are critical cooling structures that enhance the temperature-bearing capacity of turbine blades. Irregularly shaped holes, such as laidback fan-shaped holes (LFSHs), have been demonstrated to exhibit superior cooling performance compared to traditional circular holes. However, the complex shapes and structures pose significant challenges for femtosecond laser processing. Due to the extremely limited reports available, the dependency of femtosecond laser processing on the formation of irregularly shaped holes has not yet been well understood. In this paper, the fabrication process of the LFSH expansion sections and the influence of defocus distance are discussed in detail. By systematically characterizing the surface micro- and nanostructures, three-dimensional topography, and roughness of the expansion sections, the processing differences under positive defocus, zero defocus, and negative defocus are compared. The formation mechanisms of the micro-hole structures on the expansion sections under positive defocus and zero defocus are elaborated by incrementally increasing the number of processing cycles. Under negative defocus, only a smooth honeycomb-like structure forms on the surface of the expansion section, yielding the highest surface quality. Under different processing times, the roughness under negative defocus can be reduced by up to 84.8% and 95.8% compared to zero defocus and positive defocus, respectively. Furthermore, a correlation between the surface micro-hole structure and the edge structure of the hole walls is established. Full article

(This article belongs to the Special Issue Lasers and Complex System Dynamics)

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29 pages, 10657 KB

Open AccessArticle

MLP-LSTM-Attention Algorithm for DAS Cable Intrusion Detection Based on Multi-Domain Feature Fusion

by Li Yuan, Jun Xing, Bowen Shen, Yuancheng Du, Wenchi Wei and Xicheng Rao

Photonics 2026, 13(8), 768; https://doi.org/10.3390/photonics13080768 - 14 Aug 2026

Underground cables are critical infrastructure for electrical power and communication transmission, and their reliable operation is of paramount importance to urban public safety. Although Distributed Acoustic Sensing (DAS) enables wide-range, continuous, and real-time monitoring, traditional DAS signal processing methods suffer from poor intrusion [...] Read more.

Underground cables are critical infrastructure for electrical power and communication transmission, and their reliable operation is of paramount importance to urban public safety. Although Distributed Acoustic Sensing (DAS) enables wide-range, continuous, and real-time monitoring, traditional DAS signal processing methods suffer from poor intrusion discrimination and weak anti-interference capability. To address these limitations, we propose a dual-branch network based on multi-domain feature fusion, integrating a Multilayer Perceptron, a Long Short-Term Memory network (LSTM), and an attention mechanism. Vibration signals corresponding to four representative high-risk intrusion events were acquired through controlled field experiments, and a standardized, category-balanced dataset was constructed accordingly. Time-domain, frequency-domain and joint time-frequency features were extracted and mapped through a time-frequency weighting transformation to form one branch of the network, while the parallel branch employed an LSTM to capture long-range temporal dependencies. A multi-head attention mechanism enables deep adaptive fusion of two types of modal information and overcomes the limitations of conventional simple feature concatenation. Comparative experiments against KNN, 1D-CNN and LSTM baselines demonstrate that the proposed model achieves a test accuracy of 98.89%, outperforming all reference methods. Ablation studies further validate the necessity and effectiveness of each constituent module within the proposed architecture. The results indicate that this approach provides reliable support for DAS-based online monitoring of power cables against external damage. Full article

(This article belongs to the Special Issue Recent Advances in Infrared Lasers and Applications)

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13 pages, 1999 KB

Open AccessArticle

Self-Powered Broadband Photodetector Based on MoSe₂/SnS₂ Van der Waals Heterostructure

by Donglin Wang, Tianhao Feng, Ziyan Li, Xuezhen Zhai, Dewei Liu, Jimin Shang and Lamei Zhang

Photonics 2026, 13(8), 767; https://doi.org/10.3390/photonics13080767 - 14 Aug 2026

The increasing demand for broadband and self-powered optoelectronic devices has stimulated the development of two-dimensional (2D) material-based photodetectors. Here, we construct a self-powered photodetector based on a MoSe₂/SnS₂ van der Waals (vdW) heterostructure. The unique combination of MoSe₂ and [...] Read more.

The increasing demand for broadband and self-powered optoelectronic devices has stimulated the development of two-dimensional (2D) material-based photodetectors. Here, we construct a self-powered photodetector based on a MoSe₂/SnS₂ van der Waals (vdW) heterostructure. The unique combination of MoSe₂ and SnS₂ provides complementary light absorption and a type-II band alignment, which generates an interfacial built-in electric field to facilitate photogenerated carrier separation and transport, enabling efficient self-powered operation without external bias. The device exhibits a broad spectral photoresponse from ultraviolet (UV) to infrared (IR) wavelengths (350–1050 nm). Under zero bias, the photodetector achieves a responsivity of 0.6 mA/W and a rapid response time of 5.8/6.1 ms (rise/fall) under 405 nm illumination, demonstrating effective self-driven photoresponse. With an applied reverse bias of −2 V, the device further reaches a responsivity of 161 mA/W and a detectivity of 8.6 × 10¹⁰ Jones under 405 nm illumination. In addition, the device exhibits a low dark current of 5 pA and a high on/off ratio of 1180. These results demonstrate the potential of the MoSe₂/SnS₂ vdW heterostructure for broadband and self-powered optoelectronic applications. Full article

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14 pages, 5142 KB

Open AccessArticle

Comprehensive Numerical Investigation of CO₂-Laser-Driven Terahertz Generation in GaP and ZnTe Crystals

by Gabit Nazymbekov, Gyula Polónyi, Luis Nasi and György Tóth

Photonics 2026, 13(8), 766; https://doi.org/10.3390/photonics13080766 - 14 Aug 2026

GaP and ZnTe semiconductor crystals are numerically investigated for terahertz (THz) generation driven by ultrafast 10.6 µm CO₂ laser pumping. At this wavelength, low-order multiphoton absorption is effectively suppressed, enabling the study of intrinsic performance limits governed by nonlinear optical effects, material [...] Read more.

GaP and ZnTe semiconductor crystals are numerically investigated for terahertz (THz) generation driven by ultrafast 10.6 µm CO₂ laser pumping. At this wavelength, low-order multiphoton absorption is effectively suppressed, enabling the study of intrinsic performance limits governed by nonlinear optical effects, material dispersion, and THz absorption. A one-plus-one-dimensional (1+1D) frequency domain propagation model is employed, including optical rectification, cascaded nonlinear interactions, self-phase modulation, second-harmonic generation, and pulse-front-tilt-related dispersion. The simulations reveal markedly different behavior in the two crystals. In ZnTe, the large effective nonlinear coefficient enables conversion efficiencies exceeding 1% while maintaining good THz pulse quality. In GaP, strong self-phase modulation and nonlinear pulse compression can enhance the predicted efficiency but at the cost of waveform distortion and increased damage risk. MV/cm-level THz electric fields are predicted in both materials; however, ZnTe provides a more favorable compromise between conversion efficiency and pulse quality. The results provide practical guidelines for optimizing CO₂-laser-driven semiconductor THz sources. Full article

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

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14 pages, 7792 KB

Open AccessArticle

A Focusing Diffractive Optical Element for Flat-Top Beam Shaping Resilient to Etching Depth Errors

by Xiaohua Zeng, Hui Pang, Cheng Xu, Axiu Cao, Yongqi Fu and Qiling Deng

Photonics 2026, 13(8), 765; https://doi.org/10.3390/photonics13080765 - 14 Aug 2026

Diffractive optical elements (DOEs) have become core components for converting Gaussian beams into flat-top beams due to their advantages of flexible design, compact size, and precise control over light field distribution. However, during the fabrication of multi-step DOEs, some processes such as ion [...] Read more.

Diffractive optical elements (DOEs) have become core components for converting Gaussian beams into flat-top beams due to their advantages of flexible design, compact size, and precise control over light field distribution. However, during the fabrication of multi-step DOEs, some processes such as ion beam etching tend to produce etching depth errors, which cause deviations of the surface micro–nano phase structures from the designed values and thus severely degrade the beam shaping performance. This paper proposes a focusing DOE for flat-top beam shaping, which combines the focusing phase with the phase optimized by the weighted constraint iterative algorithm to establish a phase distribution resilient to etching depth errors. Thus, the proposed focusing DOE exhibits significantly improved robustness to etching depth errors and effectively reduces the structural complexity of laser optical systems. Our experimental results show that the designed DOE can stably convert the incident Gaussian beam into flat-top beams within the etching depth error range of ±30 nm, with both the flat-top beam uniformity and diffraction efficiency above 95%, and the maximum tolerable etching depth error reaches ±90 nm. Full article

(This article belongs to the Special Issue Diffractive Optics and Its Emerging Applications)

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18 pages, 2003 KB

Open AccessArticle

Global Dynamical Analysis, Sensitivity Assessment and Optical Soliton Solutions of the Truncated M-Fractional Stochastic Biswas–Arshed Model

by Ou Liao and Zhao Li

Photonics 2026, 13(8), 764; https://doi.org/10.3390/photonics13080764 - 14 Aug 2026

This work investigates the optical soliton solutions and their dynamical behaviors of the fractional stochastic Biswas–Arshed equation (FSBAE). By employing the definition of truncated M-fractional derivative and a wave transformation, we reduce the FSBAE to an integrable ordinary differential equation. Applying the qualitative [...] Read more.

This work investigates the optical soliton solutions and their dynamical behaviors of the fractional stochastic Biswas–Arshed equation (FSBAE). By employing the definition of truncated M-fractional derivative and a wave transformation, we reduce the FSBAE to an integrable ordinary differential equation. Applying the qualitative and bifurcation theory of planar dynamical systems, we analyze its bifurcations and construct five explicit types of exact traveling wave solutions, namely solitary wave solutions, kink-type exponential function solutions, Jacobi elliptic sn-type periodic solutions, Jacobi elliptic cn-type periodic solutions, and exponential-form solitary wave solutions. Furthermore, to explore the model’s sensitivity to perturbations, we introduce a time-periodic perturbation term, then the emergence of chaotic behavior is demonstrated by providing 2D and 3D phase portraits. Full article

(This article belongs to the Special Issue New Trends in Optical Solitons: Theory, Computation and Applications)

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12 pages, 29848 KB

Open AccessCommunication

Correlative Scanning Electron and Super-Resolution Structured Illumination Microscopy

by Joseph R. Hamilton, Summer K. Levis and Guy M. Hagen

Photonics 2026, 13(8), 763; https://doi.org/10.3390/photonics13080763 - 14 Aug 2026

Correlative microscopy techniques are used for many different applications in the biological sciences because the comparison of different imaging methods allows researchers to gain more and often complementary information about their samples. Correlative light and electron microscopy (CLEM) methods have been developed to [...] Read more.

Correlative microscopy techniques are used for many different applications in the biological sciences because the comparison of different imaging methods allows researchers to gain more and often complementary information about their samples. Correlative light and electron microscopy (CLEM) methods have been developed to preserve biological samples to withstand the harsh environments necessary for electron microscopy. After first being imaged using widefield (WF) and super-resolution structured illumination fluorescence microscopy (SIM), a NanoSuit chemical treatment was applied to a mammalian tissue sample before imaging with scanning electron microscopy (SEM). This was done to compare the image quality and resolution of each technique. SEM yields higher resolution and offers validation of results from SIM. Full article

(This article belongs to the Special Issue New Insights in Optical Manipulation Techniques: From Fundamental Advances to Biomedical Applications)

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9 pages, 1042 KB

Open AccessArticle

Compact High-Energy High-Beam-Quality Long-Wave Infrared BGSe-OPO

by Fangjie Li, Jintian Bian, Hui Kong, Zhonghe Wang, Haiping Xu, Yuntao Xie and Ke Sun

Photonics 2026, 13(8), 762; https://doi.org/10.3390/photonics13080762 - 13 Aug 2026

Existing long-wave infrared (LWIR) BaGa₄Se₇ optical parametric oscillators (BGSe-OPOs) adopt linear-cavity configurations yet struggle to balance high beam quality and high output energy. To overcome this limitation, we report a compact Type I phase-matched ring cavity BGSe-OPO pumped by a [...] Read more.

Existing long-wave infrared (LWIR) BaGa₄Se₇ optical parametric oscillators (BGSe-OPOs) adopt linear-cavity configurations yet struggle to balance high beam quality and high output energy. To overcome this limitation, we report a compact Type I phase-matched ring cavity BGSe-OPO pumped by a 1.06 μm laser. Operating at 8.5 μm, the OPO generates 1.2 mJ single pulses with a peak power of 0.25 MW and an optical-to-optical conversion efficiency of 2%. The estimated beam quality factor M² is 9, representing a threefold enhancement relative to linear-cavity under identical pump conditions. The system features a compact footprint of 400 × 200 mm² and a far-field divergence angle of 4 mrad after 6× beam expansion, enabling practical applications in far-field monitoring. Full article

(This article belongs to the Special Issue Long-Wave Infrared Lasers and Applications)

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7 pages, 919 KB

Open AccessCommunication

Switchable Dual-Wavelength Yellow-Green Laser at 556 nm and 560 nm Based on KYW Raman Conversion

by Yaling Yang, Yuanqing Wang, Lei Guo, Haiping Xu, Hao Zhang, Hui Kong and Jintian Bian

Photonics 2026, 13(8), 761; https://doi.org/10.3390/photonics13080761 - 13 Aug 2026

A high-efficiency extra-cavity Raman generator is demonstrated using a potassium yttrium tungstate (KYW) crystal for the first time, achieving switchable yellow-green laser output at 556 nm and 560 nm. The KYW Raman crystal is single-pass pumped by 532 nm green light, which is [...] Read more.

A high-efficiency extra-cavity Raman generator is demonstrated using a potassium yttrium tungstate (KYW) crystal for the first time, achieving switchable yellow-green laser output at 556 nm and 560 nm. The KYW Raman crystal is single-pass pumped by 532 nm green light, which is obtained by the second-harmonic generation of a 1064 nm flash-lamp-pumped Nd:YAG electro-optic (EO) Q-switched laser. When the incident pump energy at 1064 nm is 156 mJ under a repetition rate of 1 Hz, the maximum output energy reaches 51.3 mJ at 532 nm with a slope efficiency of 41.5%. By adjusting the polarization direction of the 532 nm light, two characteristic Raman shifts of the KYW crystal can be selectively excited at 765 cm⁻¹ and 905 cm⁻¹. Furthermore, the 556 nm and 560 nm visible lasers are generated with the maximum output energies of 11.6 mJ and 16.2 mJ, corresponding to the slope efficiencies of 37.6% and 48.2%, respectively. Compared with the 532 nm pulse width (18.2 ns), an obvious Raman pulse width compression effect occurred (8.2 ns). Full article

(This article belongs to the Special Issue Ultrafast Laser Nonlinear Dynamics)

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20 pages, 7899 KB

Open AccessArticle

Illumination System Pupil-Shaping Technique Based on Integer Programming and Energy Equalization

by Yadong Han, Jie Yu, Qi Zhu and Liping Wang

Photonics 2026, 13(8), 760; https://doi.org/10.3390/photonics13080760 - 12 Aug 2026

The illumination system in extreme ultraviolet lithography (EUVL) achieves pupil shaping by adjusting the facet-matching relationship of fly’s eyes. We propose an algorithm based on integer programming and energy equalization for solving the facet-matching relationship, which constrains the energy consistency across different pupil [...] Read more.

The illumination system in extreme ultraviolet lithography (EUVL) achieves pupil shaping by adjusting the facet-matching relationship of fly’s eyes. We propose an algorithm based on integer programming and energy equalization for solving the facet-matching relationship, which constrains the energy consistency across different pupil regions, enhancing pupil performance and achieving high uniformity at the mask plane. We model an illumination system to validate the proposed algorithm. Simulation results demonstrate that the proposed algorithm successfully realizes various illumination modes, achieving a maximum pupil ellipticity of 1.94%, maximum X/Y pupil pole balance of 1.45%, and maximum quadrant pole balance of 1.82%. Furthermore, it achieved an illumination field at the mask plane with a pre-correction nonuniformity of 0.45–0.59%. Full article

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