Pub Date : 2025-12-08DOI: 10.1515/nanoph-2025-0421
Rostislav Řepa, Michal Horák, Tomáš Šikola, Vlastimil Křápek
Plasmonic antennas exploit localized surface plasmons to shape, confine, and enhance electromagnetic fields with subwavelength resolution. The field enhancement is contributed to by various effects, such as the inherent surface localization of plasmons or the plasmonic lightning-rod effect. Inspired by nanofocusing observed for propagating plasmons, we test the hypothesis that plasmonic antennas with a large cross-section represent a large charge reservoir, enabling large induced charge and field enhancement. Our study reveals that a large charge reservoir is accompanied by large radiative losses, which are the dominant factor, resulting in a low field enhancement.
{"title":"Charge reservoir as a design concept for plasmonic antennas","authors":"Rostislav Řepa, Michal Horák, Tomáš Šikola, Vlastimil Křápek","doi":"10.1515/nanoph-2025-0421","DOIUrl":"https://doi.org/10.1515/nanoph-2025-0421","url":null,"abstract":"Plasmonic antennas exploit localized surface plasmons to shape, confine, and enhance electromagnetic fields with subwavelength resolution. The field enhancement is contributed to by various effects, such as the inherent surface localization of plasmons or the plasmonic lightning-rod effect. Inspired by nanofocusing observed for propagating plasmons, we test the hypothesis that plasmonic antennas with a large cross-section represent a large charge reservoir, enabling large induced charge and field enhancement. Our study reveals that a large charge reservoir is accompanied by large radiative losses, which are the dominant factor, resulting in a low field enhancement.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"3 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145703943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-08DOI: 10.1515/nanoph-2025-0409
Qianli Qiu, Kang Li, Dongjie Zhou, Yuyang Zhang, Jinguo Zhang, Zongkun Zhang, Yan Sun, Lei Zhou, Ning Dai, Junhao Chu, Jiaming Hao
The long wavelength infrared (LWIR) range (8–14 µm) is crucial for thermal radiation detection, necessitating effective camouflage against advanced infrared technologies. Conventional camouflage approaches often rely on complicated photonic structures, facing significant implementation challenges. This study introduces a novel polarization-insensitive and angle-robust metacoating emitter for LWIR camouflage, inversely designed through a deep neural network (DNN) framework. The DNN framework facilitates the automatic optimization of the metacoating’s structural and material parameters. The resulting emitter achieves an average emissivity of 0.96 covering the LWIR range and a low emissivity of 0.25 in the other mid-infrared (MIR) region. Enhanced electromagnetic wave localization and energy dissipation, driven by high-lossy materials like bismuth and titanium, contribute to these properties. Infrared imaging confirms the emitter’s superior camouflage performance, maintain effectiveness at incident angle up to 70° while exhibiting strong polarization independence. This inverse-designed metacoating demonstrates significant potential to advance infrared camouflage technology, providing robust countermeasures against modern, wide-angle, and polarization-sensitive detection systems.
{"title":"Lithography-free subwavelength metacoatings for high thermal radiation background camouflage empowered by deep neural network","authors":"Qianli Qiu, Kang Li, Dongjie Zhou, Yuyang Zhang, Jinguo Zhang, Zongkun Zhang, Yan Sun, Lei Zhou, Ning Dai, Junhao Chu, Jiaming Hao","doi":"10.1515/nanoph-2025-0409","DOIUrl":"https://doi.org/10.1515/nanoph-2025-0409","url":null,"abstract":"The long wavelength infrared (LWIR) range (8–14 µm) is crucial for thermal radiation detection, necessitating effective camouflage against advanced infrared technologies. Conventional camouflage approaches often rely on complicated photonic structures, facing significant implementation challenges. This study introduces a novel polarization-insensitive and angle-robust metacoating emitter for LWIR camouflage, inversely designed through a deep neural network (DNN) framework. The DNN framework facilitates the automatic optimization of the metacoating’s structural and material parameters. The resulting emitter achieves an average emissivity of 0.96 covering the LWIR range and a low emissivity of 0.25 in the other mid-infrared (MIR) region. Enhanced electromagnetic wave localization and energy dissipation, driven by high-lossy materials like bismuth and titanium, contribute to these properties. Infrared imaging confirms the emitter’s superior camouflage performance, maintain effectiveness at incident angle up to 70° while exhibiting strong polarization independence. This inverse-designed metacoating demonstrates significant potential to advance infrared camouflage technology, providing robust countermeasures against modern, wide-angle, and polarization-sensitive detection systems.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"4 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-08DOI: 10.1515/nanoph-2025-0479
Stefanos Fr. Koufidis, Zeki Hayran, Francesco Monticone, John B. Pendry, Martin W. McCall
Optical analog computing enables powerful functionalities, including spatial differentiation, image processing, and ultrafast linear operations. Yet, most existing approaches rely on resonant or periodic structures, whose performance is strongly wavelength-dependent, imposing bandwidth limitations and demanding stringent fabrication tolerances. Here, to address some of these challenges, we introduce a highly tunable platform for optical processing, composed of two cascaded uniform slabs exhibiting both circular and linear birefringence, whose response exhibits features relevant to optical processing without relying on resonances. Specifically, using a coupled-wave theory framework we show that sharp reflection minima, referred to as spectral holes, emerge from destructive interference between counter-propagating circularly polarized waves in uniform birefringent slabs, and can be engineered solely through parameter tuning without requiring any spatial periodicity. When operated in the negative-refraction regime enabled by giant chirality, the interference response acquires a highly parabolic form around the reflection minimum, giving rise to a polarization-selective Laplacian-like operator that performs accurate spatial differentiation over a broad spatial-frequency range. This functionality is demonstrated through an edge-detection proof of concept. The required material parameters align closely with recent experimental demonstrations of giant, tunable chirality via meta-optics, presenting a promising pathway towards compact and reconfigurable platforms for all-optical pattern recognition and image restoration.
{"title":"Chirality-driven all-optical image differentiation","authors":"Stefanos Fr. Koufidis, Zeki Hayran, Francesco Monticone, John B. Pendry, Martin W. McCall","doi":"10.1515/nanoph-2025-0479","DOIUrl":"https://doi.org/10.1515/nanoph-2025-0479","url":null,"abstract":"Optical analog computing enables powerful functionalities, including spatial differentiation, image processing, and ultrafast linear operations. Yet, most existing approaches rely on resonant or periodic structures, whose performance is strongly wavelength-dependent, imposing bandwidth limitations and demanding stringent fabrication tolerances. Here, to address some of these challenges, we introduce a highly tunable platform for optical processing, composed of two cascaded uniform slabs exhibiting both circular and linear birefringence, whose response exhibits features relevant to optical processing without relying on resonances. Specifically, using a coupled-wave theory framework we show that sharp reflection minima, referred to as spectral holes, emerge from destructive interference between counter-propagating circularly polarized waves in uniform birefringent slabs, and can be engineered solely through parameter tuning without requiring any spatial periodicity. When operated in the negative-refraction regime enabled by giant chirality, the interference response acquires a highly parabolic form around the reflection minimum, giving rise to a polarization-selective Laplacian-like operator that performs accurate spatial differentiation over a broad spatial-frequency range. This functionality is demonstrated through an edge-detection proof of concept. The required material parameters align closely with recent experimental demonstrations of giant, tunable chirality via meta-optics, presenting a promising pathway towards compact and reconfigurable platforms for all-optical pattern recognition and image restoration.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"133 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145696981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-08DOI: 10.1515/nanoph-2025-0504
Tetsuhito Omori, Kentaro Iwami
Metasurface holography is a promising technology for next-generation 3D displays, however, conventional approaches for full-colorization have faced challenges. Wavelength multiplexing based on spatial segmentation/interleaving inevitably reduces pixel density, while techniques reliant on the Pancharatnam–Berry (PB) phase are inherently polarization-dependent and have a theoretical efficiency limit of 50 %. In this work, we propose and experimentally demonstrate a design strategy that overcomes these limitations. The core of our approach is a single, polarization-independent meta-atom, realized with cross-shaped nanopillars made of silicon nitride (SiN), which enables the simultaneous and independent phase control over the three primary colors required for faithful 3D image reconstruction. This single-unit strategy surpasses the pixel density limitations of wavelength multiplexing. Furthermore, we combine this innovation with crosstalk elimination via spatial division of target 3D images and precise angle correction to ensure high-fidelity, superimposed reconstruction. Experimentally, we have successfully reconstructed high-definition, noise-free 3D full-color holograms. Our work resolves the critical limitations of pixel density and polarization dependence in metasurface holography, providing a robust pathway toward practical, high-performance holographic displays.
{"title":"Wavelength- and angle-multiplexed full-color 3D metasurface hologram","authors":"Tetsuhito Omori, Kentaro Iwami","doi":"10.1515/nanoph-2025-0504","DOIUrl":"https://doi.org/10.1515/nanoph-2025-0504","url":null,"abstract":"Metasurface holography is a promising technology for next-generation 3D displays, however, conventional approaches for full-colorization have faced challenges. Wavelength multiplexing based on spatial segmentation/interleaving inevitably reduces pixel density, while techniques reliant on the Pancharatnam–Berry (PB) phase are inherently polarization-dependent and have a theoretical efficiency limit of 50 %. In this work, we propose and experimentally demonstrate a design strategy that overcomes these limitations. The core of our approach is a single, polarization-independent meta-atom, realized with cross-shaped nanopillars made of silicon nitride (SiN), which enables the simultaneous and independent phase control over the three primary colors required for faithful 3D image reconstruction. This single-unit strategy surpasses the pixel density limitations of wavelength multiplexing. Furthermore, we combine this innovation with crosstalk elimination via spatial division of target 3D images and precise angle correction to ensure high-fidelity, superimposed reconstruction. Experimentally, we have successfully reconstructed high-definition, noise-free 3D full-color holograms. Our work resolves the critical limitations of pixel density and polarization dependence in metasurface holography, providing a robust pathway toward practical, high-performance holographic displays.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"65 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145703941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-08DOI: 10.1515/nanoph-2025-0495
Alberto Santonocito, Alessio Gabbani, Barbara Patrizi, Guido Toci, Francesco Pineider
Static metasurfaces offer precise control over light but lack reconfigurability, limiting their use in dynamic applications. Introducing tunability via external stimuli, such as magnetic fields, enables active control of their optical response, broadening their functionality. In this computational study, we present the design of a metal–dielectric–metal magnetoplasmonic metasurface with improved magnetic field tunability, surpassing the magneto-optical response of unstructured ferromagnetic materials. This improvement arises from the synergistic effect of localized plasmon excitation, surface lattice resonance, and Fabry–Pérot cavity modes. The design approach presented here consists in matching the characteristic resonance frequencies of the three phenomena by iteratively adjusting the structural parameters of the metasurface: nanostructure size, lattice period, and cavity layer thickness. This optimization led to a substantial enhancement in the reflectance modulation induced by an external magnetic field, with the overall contrast exceeding that of an unstructured cavity by more than an order of magnitude across various regions of the visible to near-infrared spectrum, under relatively low magnetic fields. This unique capability makes the system a promising tool for magnetic field-sensitive optical modulation of reflected light intensity, with potential applications as a laser amplitude modulator.
{"title":"Synergistic enhancement of magneto-optical response in cobalt-based metasurfaces via plasmonic, lattice, and cavity modes","authors":"Alberto Santonocito, Alessio Gabbani, Barbara Patrizi, Guido Toci, Francesco Pineider","doi":"10.1515/nanoph-2025-0495","DOIUrl":"https://doi.org/10.1515/nanoph-2025-0495","url":null,"abstract":"Static metasurfaces offer precise control over light but lack reconfigurability, limiting their use in dynamic applications. Introducing tunability via external stimuli, such as magnetic fields, enables active control of their optical response, broadening their functionality. In this computational study, we present the design of a metal–dielectric–metal magnetoplasmonic metasurface with improved magnetic field tunability, surpassing the magneto-optical response of unstructured ferromagnetic materials. This improvement arises from the synergistic effect of localized plasmon excitation, surface lattice resonance, and Fabry–Pérot cavity modes. The design approach presented here consists in matching the characteristic resonance frequencies of the three phenomena by iteratively adjusting the structural parameters of the metasurface: nanostructure size, lattice period, and cavity layer thickness. This optimization led to a substantial enhancement in the reflectance modulation induced by an external magnetic field, with the overall contrast exceeding that of an unstructured cavity by more than an order of magnitude across various regions of the visible to near-infrared spectrum, under relatively low magnetic fields. This unique capability makes the system a promising tool for magnetic field-sensitive optical modulation of reflected light intensity, with potential applications as a laser amplitude modulator.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"11 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145703946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Most light-emitting devices based on quantum-confined structures are commonly utilized as electrically injected devices. However, the electric-field-dependent energy band gap induced by the quantum confinement Stark effect (QCSE) usually hinders the realization of frequency-stable laser devices. This is because the change in the energy band gap, which also means the corresponding change in the photon energy, will result in an electric-field-dependent frequency. Here, we propose a novel approach to mitigate this electric-field-dependent variation in the energy band gap by employing a gradient quantum system. In this system, the energy band edges are inclined due to the action of the indium (In)-segregation effect. This special design can effectively weaken the changes in the band profile associated with the electric field effect and counteract the electric-field-dependent band gap variations within the active region to a certain extent. Experimental studies indicate that the energy band gap of this gradient quantum system remains almost unchanged (<18.9 μeV cm 2 /A) even under a relatively strong applied electric field. Meanwhile, compared with the traditional GaAs quantum well, the efficiency improvement in the band gap stability of our nanowire–well gradient system is 64.1 % and 70.6 % for the TE and TM polarization modes, respectively, which suggests that our proposed gradient quantum structure can significantly mitigate the electric-field-induced change in the energy band gap. This achievement is of great significance for advancing the development of high-performance frequency-stable laser devices in some advanced fields, such as quantum sensing systems and optical communications.
大多数基于量子约束结构的发光器件通常用作电注入器件。然而，由量子约束斯塔克效应（QCSE）引起的电场相关能带隙通常阻碍了频率稳定激光器件的实现。这是因为能带隙的变化，也意味着光子能量的相应变化，将导致与电场相关的频率。在这里，我们提出了一种新的方法，通过使用梯度量子系统来减轻这种电场依赖的能带隙变化。在该体系中，由于铟（In）偏析效应的作用，能带边缘发生倾斜。这种特殊的设计可以有效地减弱与电场效应相关的带廓变化，并在一定程度上抵消有源区内电场相关的带隙变化。实验研究表明，在较强的外加电场作用下，该梯度量子系统的能带几乎保持不变（18.9 μeV cm 2 /A）。同时，与传统的GaAs量子阱相比，我们的纳米线-阱梯度系统在TE和TM极化模式下的带隙稳定性效率分别提高了64.1%和70.6%，这表明我们提出的梯度量子结构可以显著减轻电场引起的带隙变化。这一成果对于推进量子传感系统、光通信等先进领域高性能稳频激光器件的发展具有重要意义。
{"title":"Mitigate the variation of energy band gap with electric field induced by quantum confinement Stark effect via a gradient quantum system for frequency-stable laser diodes","authors":"Yuhong Wang, Yiwei Zhang, Zihan Jiang, Jian Wu, Chunqing Gao","doi":"10.1515/nanoph-2025-0380","DOIUrl":"https://doi.org/10.1515/nanoph-2025-0380","url":null,"abstract":"Most light-emitting devices based on quantum-confined structures are commonly utilized as electrically injected devices. However, the electric-field-dependent energy band gap induced by the quantum confinement Stark effect (QCSE) usually hinders the realization of frequency-stable laser devices. This is because the change in the energy band gap, which also means the corresponding change in the photon energy, will result in an electric-field-dependent frequency. Here, we propose a novel approach to mitigate this electric-field-dependent variation in the energy band gap by employing a gradient quantum system. In this system, the energy band edges are inclined due to the action of the indium (In)-segregation effect. This special design can effectively weaken the changes in the band profile associated with the electric field effect and counteract the electric-field-dependent band gap variations within the active region to a certain extent. Experimental studies indicate that the energy band gap of this gradient quantum system remains almost unchanged (<18.9 μeV cm <jats:sup>2</jats:sup> /A) even under a relatively strong applied electric field. Meanwhile, compared with the traditional GaAs quantum well, the efficiency improvement in the band gap stability of our nanowire–well gradient system is 64.1 % and 70.6 % for the TE and TM polarization modes, respectively, which suggests that our proposed gradient quantum structure can significantly mitigate the electric-field-induced change in the energy band gap. This achievement is of great significance for advancing the development of high-performance frequency-stable laser devices in some advanced fields, such as quantum sensing systems and optical communications.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"19 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145703945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-08DOI: 10.1515/nanoph-2025-0429
Alessandra Sabatti, Jost Kellner, Robert J. Chapman, Rachel Grange
Nonlinear frequency conversion offers powerful capabilities for applications in telecommunications, signal processing, and computing. Thin-film lithium niobate (TFLN) has emerged as a promising integrated photonics platform due to its strong electro-optic effect and second-order nonlinearity, which can be exploited through periodic poling. However, conventional poling techniques in x-cut TFLN are constrained to minimum period sizes on the order of microns, restricting access to highly phase-mismatched interactions such as counter- and backward-propagating frequency conversion. In this work, we demonstrate scalable periodic poling of x-cut TFLN with domains periods as short as 215 nm and realize devices that support both counter- and back-propagating phase matching. We estimate conversion efficiencies of 1,474 %/W/cm 2 and 45 %/W/cm 2 for the two interaction types, respectively. Sum frequency generation measurements confirm that the nonlinear generation takes place in the desired direction. Furthermore, we report spontaneous parametric down conversion for the counter-propagating configuration and, for the first time, for a backward propagating device. This breakthrough provides unprecedented control over engineering of ferroelectric domain geometries in TFLN, leading into the generation of photon pairs with precisely tailored spatial and spectral characteristics. Such capabilities hold strong potential for advancing quantum signal processing, scalable quantum computing architectures, and precision quantum metrology.
{"title":"Nanodomain poling unlocking backward nonlinear light generation in thin film lithium niobate","authors":"Alessandra Sabatti, Jost Kellner, Robert J. Chapman, Rachel Grange","doi":"10.1515/nanoph-2025-0429","DOIUrl":"https://doi.org/10.1515/nanoph-2025-0429","url":null,"abstract":"Nonlinear frequency conversion offers powerful capabilities for applications in telecommunications, signal processing, and computing. Thin-film lithium niobate (TFLN) has emerged as a promising integrated photonics platform due to its strong electro-optic effect and second-order nonlinearity, which can be exploited through periodic poling. However, conventional poling techniques in x-cut TFLN are constrained to minimum period sizes on the order of microns, restricting access to highly phase-mismatched interactions such as counter- and backward-propagating frequency conversion. In this work, we demonstrate scalable periodic poling of x-cut TFLN with domains periods as short as 215 nm and realize devices that support both counter- and back-propagating phase matching. We estimate conversion efficiencies of 1,474 %/W/cm <jats:sup>2</jats:sup> and 45 %/W/cm <jats:sup>2</jats:sup> for the two interaction types, respectively. Sum frequency generation measurements confirm that the nonlinear generation takes place in the desired direction. Furthermore, we report spontaneous parametric down conversion for the counter-propagating configuration and, for the first time, for a backward propagating device. This breakthrough provides unprecedented control over engineering of ferroelectric domain geometries in TFLN, leading into the generation of photon pairs with precisely tailored spatial and spectral characteristics. Such capabilities hold strong potential for advancing quantum signal processing, scalable quantum computing architectures, and precision quantum metrology.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"22 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145703940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-08DOI: 10.1515/nanoph-2025-0512
Yasuhiro Tamayama, Yugo Shibata
We propose and validate a method for designing a broadband variable beamsplitter using a metamaterial with subwavelength thickness. Through theoretical analysis and numerical simulations, we demonstrate that the reflectance-to-transmittance ratio of a single-layer resonant metamaterial at its resonance frequency can be controlled by varying the spatial arrangement of the constituent meta-atoms, without altering their individual structures. Building on this theory, we further conjecture a method for achieving a frequency-independent reflectance-to-transmittance ratio across a broad spectral range. Numerical results confirm that a metamaterial with subwavelength thickness can be engineered to function as a broadband variable beamsplitter using the proposed approach. These findings contribute to the advancement of techniques for splitting and combining electromagnetic waves in compact systems.
{"title":"Broadband variable beamsplitter made of a subwavelength-thick metamaterial","authors":"Yasuhiro Tamayama, Yugo Shibata","doi":"10.1515/nanoph-2025-0512","DOIUrl":"https://doi.org/10.1515/nanoph-2025-0512","url":null,"abstract":"We propose and validate a method for designing a broadband variable beamsplitter using a metamaterial with subwavelength thickness. Through theoretical analysis and numerical simulations, we demonstrate that the reflectance-to-transmittance ratio of a single-layer resonant metamaterial at its resonance frequency can be controlled by varying the spatial arrangement of the constituent meta-atoms, without altering their individual structures. Building on this theory, we further conjecture a method for achieving a frequency-independent reflectance-to-transmittance ratio across a broad spectral range. Numerical results confirm that a metamaterial with subwavelength thickness can be engineered to function as a broadband variable beamsplitter using the proposed approach. These findings contribute to the advancement of techniques for splitting and combining electromagnetic waves in compact systems.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"1 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145703944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-08DOI: 10.1515/nanoph-2025-0515
Juwon Jung, Leeju Hwang, Nagyeong Kim, Kibaek Kim, Seri Kim, Jongkyoon Park, Won Chegal, Yong Jai Cho, Young-Joo Kim
Spectroscopic ellipsometry (SE) is a powerful, non-destructive technique for nanoscale structural characterization. However, conventional SE data analysis typically assumes perfectly periodic specimen structures, overlooking fabrication-induced structural variations and thereby reducing the accuracy of predicted structural parameters. We have developed an enhanced analysis framework that explicitly accounts for both nanoscale structural variations and measurement-angle misalignment by introducing the concept of an average Mueller matrix (MM), which represents statistical distributions of nanoscale structures. In addition, we introduce a high-throughput MM-generation neural network that enables rapid data preparation by approximating rigorous coupled-wave analysis (RCWA) simulations for large numbers of specimens across a broad range of structural parameters. The model achieves a mean-squared error of 9.99 × 10 −8 MSE when validated against RCWA-simulated MM data for one-dimensional SiO 2 nanogratings. Finally, we apply our analysis framework to experimentally measured MM data, achieving highly accurate dimensional predictions with errors below 0.4 nm when compared with structural parameters measured by scanning electron microscopy (SEM). We believe that this analysis algorithm significantly advances the potential for high-precision SE-based metrology in semiconductor, photonic, and display manufacturing.
{"title":"AI-based analysis algorithm incorporating nanoscale structural variations and measurement-angle misalignment in spectroscopic ellipsometry","authors":"Juwon Jung, Leeju Hwang, Nagyeong Kim, Kibaek Kim, Seri Kim, Jongkyoon Park, Won Chegal, Yong Jai Cho, Young-Joo Kim","doi":"10.1515/nanoph-2025-0515","DOIUrl":"https://doi.org/10.1515/nanoph-2025-0515","url":null,"abstract":"Spectroscopic ellipsometry (SE) is a powerful, non-destructive technique for nanoscale structural characterization. However, conventional SE data analysis typically assumes perfectly periodic specimen structures, overlooking fabrication-induced structural variations and thereby reducing the accuracy of predicted structural parameters. We have developed an enhanced analysis framework that explicitly accounts for both nanoscale structural variations and measurement-angle misalignment by introducing the concept of an average Mueller matrix (MM), which represents statistical distributions of nanoscale structures. In addition, we introduce a high-throughput MM-generation neural network that enables rapid data preparation by approximating rigorous coupled-wave analysis (RCWA) simulations for large numbers of specimens across a broad range of structural parameters. The model achieves a mean-squared error of 9.99 × 10 <jats:sup>−8</jats:sup> MSE when validated against RCWA-simulated MM data for one-dimensional SiO <jats:sub>2</jats:sub> nanogratings. Finally, we apply our analysis framework to experimentally measured MM data, achieving highly accurate dimensional predictions with errors below 0.4 nm when compared with structural parameters measured by scanning electron microscopy (SEM). We believe that this analysis algorithm significantly advances the potential for high-precision SE-based metrology in semiconductor, photonic, and display manufacturing.","PeriodicalId":19027,"journal":{"name":"Nanophotonics","volume":"134 1","pages":""},"PeriodicalIF":7.5,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145703974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-08DOI: 10.1515/nanoph-2025-0456
Joshua T. Y. Tse, Taisuke Enomoto, Shunsuke Murai, Katsuhisa Tanaka
Bound states in the continuum (BIC) exhibit extremely high quality factors due to the lack of radiation loss and thus are widely studied for Purcell enhancement. However, a closer examination reveals that the enhancement is absent at the BIC due to the lack of out-coupling capability, but the strong enhancement is only observed at nearby configuration, namely quasi -BIC. To study this unique behavior of the Purcell enhancement near BIC, we built an analytical model with spectral parameters to analyze the Purcell enhancement on metasurfaces supporting quasi -BIC. Our analytical model predicts the average Purcell enhancement by metasurfaces coupled to a luminescent medium, utilizing parameters that are formulated through the temporal coupled-mode theory and can be derived from measured spectra such as transmissivity and reflectivity. We analyzed several metasurfaces supporting quasi -BIC numerically and experimentally to study the behavior of the spectral parameters as well as the resultant Purcell enhancement. We formulated the interdependence between the quality factor and the out-coupling efficiency, and revealed the existence of optimal detuning from the BIC. We also discovered that our findings are general and applicable towards realistic metasurfaces that are lossy and/or asymmetric. This discovery provides an intuitive model to understand the modal qualities of quasi -BIC and will facilitate optimization of quasi -BIC for luminescence enhancement applications.
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