Pub Date : 2026-01-24DOI: 10.1016/j.ijleo.2026.172678
ZhengPing Yang , Wei-Ping Zhong , Milivoj Belić , WenYe Zhong
Controlling the shape of higher-dimensional nondiffracting beams is one of the important research topics in current beam propagation theory and engineering practice. This article investigates the three-dimensional Helmholtz equation and derives its exact beam solution, which incorporates Weber functions and a single control parameter. Building upon the nondiffracting beam solution obtained, we analyze the excited states of Weber beams for different values of the control parameter, including the fundamental state, the first excited state, and even- and odd-order Weber beams. Our findings reveal that the fundamental state of Weber beams exhibits a pancake-like shape, while the first excited state forms a tube-like shape. Odd-order beams display toroidal shapes, whereas even-order beams combine toroidal and ellipsoidal shapes. Typically, the toroidal structures exhibit vortex-type energy distributions, with higher intensities appearing at the edges of tubes, while the ellipsoidal structures display Gaussian-type energy distributions, with higher energies concentrated at the center of pancake-like regions. The method proposed in this study for constructing higher-dimensional exact solutions of the Helmholtz equation using a novel coordinate transformation can be extended to other higher-dimensional models.
{"title":"Three-dimensional nondiffracting Weber beams","authors":"ZhengPing Yang , Wei-Ping Zhong , Milivoj Belić , WenYe Zhong","doi":"10.1016/j.ijleo.2026.172678","DOIUrl":"10.1016/j.ijleo.2026.172678","url":null,"abstract":"<div><div>Controlling the shape of higher-dimensional nondiffracting beams is one of the important research topics in current beam propagation theory and engineering practice. This article investigates the three-dimensional Helmholtz equation and derives its exact beam solution, which incorporates Weber functions and a single control parameter. Building upon the nondiffracting beam solution obtained, we analyze the excited states of Weber beams for different values of the control parameter, including the fundamental state, the first excited state, and even- and odd-order Weber beams. Our findings reveal that the fundamental state of Weber beams exhibits a pancake-like shape, while the first excited state forms a tube-like shape. Odd-order beams display toroidal shapes, whereas even-order beams combine toroidal and ellipsoidal shapes. Typically, the toroidal structures exhibit vortex-type energy distributions, with higher intensities appearing at the edges of tubes, while the ellipsoidal structures display Gaussian-type energy distributions, with higher energies concentrated at the center of pancake-like regions. The method proposed in this study for constructing higher-dimensional exact solutions of the Helmholtz equation using a novel coordinate transformation can be extended to other higher-dimensional models.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"348 ","pages":"Article 172678"},"PeriodicalIF":3.1,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-01-24DOI: 10.1016/j.ijleo.2026.172680
V.V. Kotlyar , A.A. Kovalev
We introduce here new physical quantities. By analogy with the conventional orbital angular momentum (OAM), they are called polarization OAM and hybrid OAM. It is known that the conventional OAM indicates the presence of an optical vortex in the light field and is equal to the topological charge. The same way, the polarization OAM indicates the presence of a "vortex of the linear polarization direction" in the vector field and is equal to the singularity index of the vector field. Thus, it shows how many full turnovers makes the linear polarization vector along a closed contour around the optical axis. The hybrid OAM demonstrates that along a closed contour around the optical axis, the vector field changes not only by the direction of major axis of the polarization ellipse, but also by the ratio between the major and minor ellipse axes. The hybrid OAM is equal to the number of full turnovers of the polarization ellipse. These new OAMs are derived for several typical initial vector fields to demonstrate their functionality. The initial electric field has only two transverse components, which determine the longitudinal component of the OAM vector. However, at the tight focus, all three components of the E-vector arise, and therefore, longitudinal component of the OAM vector is defined by all three electric field components. Thus, if one of these three OAMs is zero in the initial field, then at the focus, this OAM can become nonzero due to appearing longitudinal field component, contributing to this OAM. We believe that these newly introduced OAMs can be applicable to other vector fields, allowing more complete description of their properties.
{"title":"Orbital angular momentum of vector light fields at the tight focus","authors":"V.V. Kotlyar , A.A. Kovalev","doi":"10.1016/j.ijleo.2026.172680","DOIUrl":"10.1016/j.ijleo.2026.172680","url":null,"abstract":"<div><div>We introduce here new physical quantities. By analogy with the conventional orbital angular momentum (OAM), they are called polarization OAM and hybrid OAM. It is known that the conventional OAM indicates the presence of an optical vortex in the light field and is equal to the topological charge. The same way, the polarization OAM indicates the presence of a \"vortex of the linear polarization direction\" in the vector field and is equal to the singularity index of the vector field. Thus, it shows how many full turnovers makes the linear polarization vector along a closed contour around the optical axis. The hybrid OAM demonstrates that along a closed contour around the optical axis, the vector field changes not only by the direction of major axis of the polarization ellipse, but also by the ratio between the major and minor ellipse axes. The hybrid OAM is equal to the number of full turnovers of the polarization ellipse. These new OAMs are derived for several typical initial vector fields to demonstrate their functionality. The initial electric field has only two transverse components, which determine the longitudinal component of the OAM vector. However, at the tight focus, all three components of the E-vector arise, and therefore, longitudinal component of the OAM vector is defined by all three electric field components. Thus, if one of these three OAMs is zero in the initial field, then at the focus, this OAM can become nonzero due to appearing longitudinal field component, contributing to this OAM. We believe that these newly introduced OAMs can be applicable to other vector fields, allowing more complete description of their properties.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"348 ","pages":"Article 172680"},"PeriodicalIF":3.1,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-01-21DOI: 10.1016/j.ijleo.2026.172675
Krishna Sarma, Divyendu Vats, Mohd Mansoor Khan
This work introduces the design and performance analysis of a hybrid optical amplifier (HOA) operating across the O+E+S+C-bands, achieved by integrating Praseodymium-doped fiber amplifiers (PDFAs), Thulium-doped fiber amplifiers (TDFAs), and Erbium-doped fiber amplifiers (EDFAs) along with a Raman amplifier (RA). The PDFA, TDFA, and EDFA modules are configured in parallel to amplify optical signals spanning from 1270–1560 nm. However, this configuration exhibits reduced gain performance in the 1360–1410 nm and 1500–1520 nm regions, yielding gains of 18 dB and 23 dB, respectively, due to the limited spectral coverage of the individual amplifier modules. To overcome these limitations, a Raman amplifier is cascaded with the PDFA–TDFA–EDFA setup to enhance gain performance in the affected regions with an average gain of 30 dB. To optimize the amplifier’s performance across the O+E+S+C-bands, a machine learning (ML) model, P2RAMnet (Pump Parameter Optimization of Raman Amplifier for Multiband Amplification), is developed to predict optimal Raman pump parameters. The model demonstrates high accuracy, with a mean squared error (MSE) of 0.5 dB2 and a mean absolute error (MAE) of 0.2 dB. Among all input features, the pump wavelength emerges as the most influential factor, as identified by SHapley Additive exPlanations (SHAP) analysis. Moreover, PDF analysis shows that the majority of prediction errors fall within 3 dB, highlighting the model’s accuracy and reliability. The pump parameters predicted by P2RAMnet suggest a pump wavelength of 1321 nm at 1500 mW for the 1360–1410 nm region, and a pump wavelength of 1400 nm at 1300 mW for the 1500–1520 nm region. The predicted parameters are validated through OptiSystem simulations, achieving gain flatness of 4 dB in the 1360–1410 nm range and 2.4 dB in the 1500–1520 nm range, while maintaining a gain of 26 dB across the 1280–1550 nm spectrum.
{"title":"ML-driven gain equalization and enhancement in O+E+S+C multiband optical fiber amplifier","authors":"Krishna Sarma, Divyendu Vats, Mohd Mansoor Khan","doi":"10.1016/j.ijleo.2026.172675","DOIUrl":"10.1016/j.ijleo.2026.172675","url":null,"abstract":"<div><div>This work introduces the design and performance analysis of a hybrid optical amplifier (HOA) operating across the O+E+S+C-bands, achieved by integrating Praseodymium-doped fiber amplifiers (PDFAs), Thulium-doped fiber amplifiers (TDFAs), and Erbium-doped fiber amplifiers (EDFAs) along with a Raman amplifier (RA). The PDFA, TDFA, and EDFA modules are configured in parallel to amplify optical signals spanning from 1270–1560 nm. However, this configuration exhibits reduced gain performance in the 1360–1410 nm and 1500–1520 nm regions, yielding gains of <span><math><mo>∼</mo></math></span>18 dB and <span><math><mo>∼</mo></math></span>23 dB, respectively, due to the limited spectral coverage of the individual amplifier modules. To overcome these limitations, a Raman amplifier is cascaded with the PDFA–TDFA–EDFA setup to enhance gain performance in the affected regions with an average gain of 30 dB. To optimize the amplifier’s performance across the O+E+S+C-bands, a machine learning (ML) model, P2RAMnet (Pump Parameter Optimization of Raman Amplifier for Multiband Amplification), is developed to predict optimal Raman pump parameters. The model demonstrates high accuracy, with a mean squared error (MSE) of <span><math><mo>∼</mo></math></span> 0.5 dB<sup>2</sup> and a mean absolute error (MAE) of <span><math><mo><</mo></math></span> 0.2 dB. Among all input features, the pump wavelength emerges as the most influential factor, as identified by SHapley Additive exPlanations (SHAP) analysis. Moreover, PDF analysis shows that the majority of prediction errors fall within <span><math><mo>±</mo></math></span>3 dB, highlighting the model’s accuracy and reliability. The pump parameters predicted by P2RAMnet suggest a pump wavelength of 1321 nm at 1500 mW for the 1360–1410 nm region, and a pump wavelength of 1400 nm at 1300 mW for the 1500–1520 nm region. The predicted parameters are validated through OptiSystem<span><math><msup><mspace></mspace><mi>®</mi></msup></math></span> simulations, achieving gain flatness of 4 dB in the 1360–1410 nm range and 2.4 dB in the 1500–1520 nm range, while maintaining a gain of <span><math><mo>></mo></math></span> 26 dB across the 1280–1550 nm spectrum.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"348 ","pages":"Article 172675"},"PeriodicalIF":3.1,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-01-19DOI: 10.1016/j.ijleo.2026.172674
A.-B.A. Mohamed , E.K. Jaradat , S.S. Alharbi
A comprehensive theoretical investigation of quantum correlations (Bell nonlocality, EPR steering, and entanglement) in a nanowire is presented. We analyze the system’s thermal state to determine how a perpendicular magnetic field, Rashba spin-orbit (RSO) interaction, and an external electric field (EEF) interact to maintain non-classicality in the presence of thermal decoherence. Our results reveal a competition between the RSO interaction, which generates the quantum resources, and the Zeeman effect from the magnetic field, which acts to suppress them. Furthermore, a resonant revival of quantum correlations driven by the EEF is demonstrated, even in regimes of high temperature and strong magnetic fields where they are suppressed. This phenomenon originates from a cancellation of the Zeeman-induced spin alignment by the EEF’s orbital perturbation, which restores the efficacy of the RSO entanglement. Specifically, we show that tuning the electric field enables the recovery of entanglement and steering at temperatures where they are otherwise extinguished. These findings highlight a pathway for dynamic control of quantum resources in solid-state spintronic devices, relevant for quantum information applications.
{"title":"Thermal robustness of nanowire quantum correlations with rashba spin-orbit interaction and external fields","authors":"A.-B.A. Mohamed , E.K. Jaradat , S.S. Alharbi","doi":"10.1016/j.ijleo.2026.172674","DOIUrl":"10.1016/j.ijleo.2026.172674","url":null,"abstract":"<div><div>A comprehensive theoretical investigation of quantum correlations (Bell nonlocality, EPR steering, and entanglement) in a nanowire is presented. We analyze the system’s thermal state to determine how a perpendicular magnetic field, Rashba spin-orbit (RSO) interaction, and an external electric field (EEF) interact to maintain non-classicality in the presence of thermal decoherence. Our results reveal a competition between the RSO interaction, which generates the quantum resources, and the Zeeman effect from the magnetic field, which acts to suppress them. Furthermore, a resonant revival of quantum correlations driven by the EEF is demonstrated, even in regimes of high temperature and strong magnetic fields where they are suppressed. This phenomenon originates from a cancellation of the Zeeman-induced spin alignment by the EEF’s orbital perturbation, which restores the efficacy of the RSO entanglement. Specifically, we show that tuning the electric field enables the recovery of entanglement and steering at temperatures where they are otherwise extinguished. These findings highlight a pathway for dynamic control of quantum resources in solid-state spintronic devices, relevant for quantum information applications.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"347 ","pages":"Article 172674"},"PeriodicalIF":3.1,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-01-17DOI: 10.1016/j.ijleo.2026.172673
Régis Donald Hontinfinde , Charbel Z.J. Mamlankou , Senan Ida Valérie Hontinfinde , Marc Amour Ayela , Gaston Edah
We present a deep learning approach for predicting the nonlinear propagation dynamics of ultrashort optical pulses in fiber-optic systems using Physics-Informed Neural Networks (PINNs). The method solves the Hirota equation, which governs femtosecond pulse propagation in long-haul optical communications by incorporating higher-order dispersion and nonlinear delay effects. By embedding physical conservation laws directly into the neural network loss function, our approach achieves high-precision predictions with absolute errors ranging from to when validated against finite-difference reference solutions. Numerical experiments across multiple parameter configurations demonstrate the robustness and computational efficiency of the PINNs framework. The predicted soliton evolution profiles reveal stable pulse propagation characteristics essential for designing next-generation high-capacity optical telecommunication systems. Our results establish PINNs as a powerful computational tool for analyzing complex nonlinear wave phenomena in optical fibers.
{"title":"Physics-informed neural networks for predicting ultrashort optical pulse dynamics in nonlinear fiber systems","authors":"Régis Donald Hontinfinde , Charbel Z.J. Mamlankou , Senan Ida Valérie Hontinfinde , Marc Amour Ayela , Gaston Edah","doi":"10.1016/j.ijleo.2026.172673","DOIUrl":"10.1016/j.ijleo.2026.172673","url":null,"abstract":"<div><div>We present a deep learning approach for predicting the nonlinear propagation dynamics of ultrashort optical pulses in fiber-optic systems using Physics-Informed Neural Networks (PINNs). The method solves the Hirota equation, which governs femtosecond pulse propagation in long-haul optical communications by incorporating higher-order dispersion and nonlinear delay effects. By embedding physical conservation laws directly into the neural network loss function, our approach achieves high-precision predictions with absolute errors ranging from <span><math><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup></math></span> to <span><math><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math></span> when validated against finite-difference reference solutions. Numerical experiments across multiple parameter configurations demonstrate the robustness and computational efficiency of the PINNs framework. The predicted soliton evolution profiles reveal stable pulse propagation characteristics essential for designing next-generation high-capacity optical telecommunication systems. Our results establish PINNs as a powerful computational tool for analyzing complex nonlinear wave phenomena in optical fibers.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"347 ","pages":"Article 172673"},"PeriodicalIF":3.1,"publicationDate":"2026-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-01-12DOI: 10.1016/j.ijleo.2026.172672
Ferhat Hanife , Yashar Azizian-Kalandaragh
Structured illumination microscopy (SIM) enables optical imaging beyond the diffraction limit by heterodyning high spatial frequencies into the observable passband of a conventional microscope. In this work, a complete numerical framework is developed to investigate how illumination pattern geometry and structural parameters influence image formation and resolution enhancement in two-dimensional SIM. Synthetic samples representing periodic arrays of polymer nanotubes are modeled under multiple illumination families, including sinusoidal, Ronchi, sawtooth, and triangular configurations. Each simulation incorporates realistic photon shot noise, detector readout noise, and the optical transfer function (OTF) of a high-numerical-aperture system. Quantitative metrics such as full width at half maximum (FWHM), intensity dip metric, modulation contrast, edge sharpness, contrast-to-noise ratio (CNR), and high-frequency spectral energy are extracted to evaluate performance as a function of fringe thickness. The results demonstrate that structured illumination significantly narrows the effective point-spread function (PSF), enhances image contrast, and recovers otherwise inaccessible high-frequency details. Non-sinusoidal patterns yield improved resolution due to their richer harmonic content, though with minor side-lobe artifacts. Generally, the proposed simulation framework provides both physical insight and practical guidance for optimizing illumination design and achieving higher fidelity in super-resolution SIM imaging.
{"title":"Numerical analysis of structured illumination microscopy: Influence of illumination pattern geometry and fringe thickness on resolution enhancement","authors":"Ferhat Hanife , Yashar Azizian-Kalandaragh","doi":"10.1016/j.ijleo.2026.172672","DOIUrl":"10.1016/j.ijleo.2026.172672","url":null,"abstract":"<div><div>Structured illumination microscopy (SIM) enables optical imaging beyond the diffraction limit by heterodyning high spatial frequencies into the observable passband of a conventional microscope. In this work, a complete numerical framework is developed to investigate how illumination pattern geometry and structural parameters influence image formation and resolution enhancement in two-dimensional SIM. Synthetic samples representing periodic arrays of polymer nanotubes are modeled under multiple illumination families, including sinusoidal, Ronchi, sawtooth, and triangular configurations. Each simulation incorporates realistic photon shot noise, detector readout noise, and the optical transfer function (OTF) of a high-numerical-aperture system. Quantitative metrics such as full width at half maximum (FWHM), intensity dip metric, modulation contrast, edge sharpness, contrast-to-noise ratio (CNR), and high-frequency spectral energy are extracted to evaluate performance as a function of fringe thickness. The results demonstrate that structured illumination significantly narrows the effective point-spread function (PSF), enhances image contrast, and recovers otherwise inaccessible high-frequency details. Non-sinusoidal patterns yield improved resolution due to their richer harmonic content, though with minor side-lobe artifacts. Generally, the proposed simulation framework provides both physical insight and practical guidance for optimizing illumination design and achieving higher fidelity in super-resolution SIM imaging.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"348 ","pages":"Article 172672"},"PeriodicalIF":3.1,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-01-12DOI: 10.1016/j.ijleo.2026.172671
P. Sushma Chowdary , V.Vijayasri Bolisetty , U. Yedukondalu , Bokkisam Venkata Sai Sailaja
In this paper, a four-port wideband MIMO antenna is developed for future 6 G wireless communication systems. The proposed disk-shaped antenna consists of four identical disk-shaped elements arranged uniformly around a circular structure. This uniform arrangement helps maintain geometric balance and minimizes mutual coupling. All the disk patterns are arranged equidistantly around the centrally etched flower-like structure, which ensures the symmetrical geometry of the proposed antenna. These slots are helpful in generating a super-wide bandwidth ranging from 1.81 THz to 4.1513 THz. To further enhance the efficiency of the antenna, hexagonal slots are etched on the ground plane. The hexagonally etched slots on the ground reduce signal reflection losses. The overall dimensions of the four-port MIMO antenna are 800 × 800 × 50 µm³ , and it is designed on a silicon substrate with a relative permittivity of 11.9. The proposed antenna achieves a super-wide bandwidth ranging from 0.926 THz to 5.5411 THz and a peak gain of 7 dB. MIMO performance parameters such as diversity gain, Total Active Reflection Coefficient (TARC), Envelope Correlation Coefficient (ECC), and Channel Capacity Loss (CCL) are evaluated, and all lie within acceptable ranges. The disk-shaped antenna demonstrates super-wideband characteristics, high resolution, and a low reflection coefficient. The disk-shaped antenna operates at 1.8175 THz, 2.5911 THz, 3.286 THz, and 4.1513 THz, with reflection coefficients of −28.02 dB, −35.723 dB, −37.11 dB, and −32.35 dB, respectively. Considering to its compact size, wide bandwidth, and stable radiation characteristics, the proposed disk-shaped antenna is well suited for high-speed THz communication and beyond-6G wireless applications.
{"title":"Performance evaluation of multi band disk-shaped terahertz MIMO antenna with hexagon slots on ground for future 6 G and terahertz communication system","authors":"P. Sushma Chowdary , V.Vijayasri Bolisetty , U. Yedukondalu , Bokkisam Venkata Sai Sailaja","doi":"10.1016/j.ijleo.2026.172671","DOIUrl":"10.1016/j.ijleo.2026.172671","url":null,"abstract":"<div><div>In this paper, a four-port wideband MIMO antenna is developed for future 6 G wireless communication systems. The proposed disk-shaped antenna consists of four identical disk-shaped elements arranged uniformly around a circular structure. This uniform arrangement helps maintain geometric balance and minimizes mutual coupling. All the disk patterns are arranged equidistantly around the centrally etched flower-like structure, which ensures the symmetrical geometry of the proposed antenna. These slots are helpful in generating a super-wide bandwidth ranging from 1.81 THz to 4.1513 THz. To further enhance the efficiency of the antenna, hexagonal slots are etched on the ground plane. The hexagonally etched slots on the ground reduce signal reflection losses. The overall dimensions of the four-port MIMO antenna are 800 × 800 × 50 µm³ , and it is designed on a silicon substrate with a relative permittivity of 11.9. The proposed antenna achieves a super-wide bandwidth ranging from 0.926 THz to 5.5411 THz and a peak gain of 7 dB. MIMO performance parameters such as diversity gain, Total Active Reflection Coefficient (TARC), Envelope Correlation Coefficient (ECC), and Channel Capacity Loss (CCL) are evaluated, and all lie within acceptable ranges. The disk-shaped antenna demonstrates super-wideband characteristics, high resolution, and a low reflection coefficient. The disk-shaped antenna operates at 1.8175 THz, 2.5911 THz, 3.286 THz, and 4.1513 THz, with reflection coefficients of −28.02 dB, −35.723 dB, −37.11 dB, and −32.35 dB, respectively. Considering to its compact size, wide bandwidth, and stable radiation characteristics, the proposed disk-shaped antenna is well suited for high-speed THz communication and beyond-6G wireless applications.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"347 ","pages":"Article 172671"},"PeriodicalIF":3.1,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
This work introduces the so-called shape artificial intelligence as an unsupervised artificial intelligence (AI) methodology for the automated design of photonic crystals (PCs) with optimized flat bands. We apply this method to a 2D square lattice PC with rotating dielectric rods, demonstrating its ability to identify geometric configurations that maximize band flatness across the Brillouin zone. These flat bands are almost unaffected when propagating past large dielectric obstacles. This suggests the potential for identifying topological properties. The results highlight the power of the RD method as a generalizable tool for advanced photonic engineering, with applications in high-density integrated circuits, nonlinear optics, and sensing.
{"title":"Flat band fine-tuning in photonic crystals via unsupervised shape artificial intelligence","authors":"J.G. Cardona , H.A. Gómez-Urrea , M.E. Mora-Ramos , F.J. Caro-Lopera","doi":"10.1016/j.ijleo.2026.172669","DOIUrl":"10.1016/j.ijleo.2026.172669","url":null,"abstract":"<div><div>This work introduces the so-called shape artificial intelligence as an unsupervised artificial intelligence (AI) methodology for the automated design of photonic crystals (PCs) with optimized flat bands. We apply this method to a 2D square lattice PC with rotating dielectric rods, demonstrating its ability to identify geometric configurations that maximize band flatness across the Brillouin zone. These flat bands are almost unaffected when propagating past large dielectric obstacles. This suggests the potential for identifying topological properties. The results highlight the power of the RD method as a generalizable tool for advanced photonic engineering, with applications in high-density integrated circuits, nonlinear optics, and sensing.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"347 ","pages":"Article 172669"},"PeriodicalIF":3.1,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-01-09DOI: 10.1016/j.ijleo.2026.172670
Oumayma Habli , Jihene Zaghdoudi , Mounir Kanzari
This work numerically investigates the optical response of a one-dimensional photonic crystal incorporating a nonlinear defect layer based on either a polymer or graphene. Using the transfer matrix method, the influence of Kerr nonlinearity on the defect-mode transmission is analyzed under linear and nonlinear regimes. The results show that graphene exhibits a significantly stronger nonlinear response than the polymer defect layer, leading to enhanced wavelength tunability and higher spectral selectivity. A key contribution of this study is the demonstration of a dual-parameter tuning mechanism that combines input optical intensity and angle of incidence, enabling dynamic compensation between intensity-induced redshift and angle-induced blueshift of the defect mode. This dual control provides improved flexibility compared to conventional single-parameter approaches. The proposed graphene-based structure offers promising potential for tunable photonic devices such as optical filters, all-optical switches, sensors, and optical limiters.
{"title":"Dual-parameter tunable high-Q optical response in 1D photonic crystals with Kerr-nonlinear graphene and polymer defect layers","authors":"Oumayma Habli , Jihene Zaghdoudi , Mounir Kanzari","doi":"10.1016/j.ijleo.2026.172670","DOIUrl":"10.1016/j.ijleo.2026.172670","url":null,"abstract":"<div><div>This work numerically investigates the optical response of a one-dimensional photonic crystal incorporating a nonlinear defect layer based on either a polymer or graphene. Using the transfer matrix method, the influence of Kerr nonlinearity on the defect-mode transmission is analyzed under linear and nonlinear regimes. The results show that graphene exhibits a significantly stronger nonlinear response than the polymer defect layer, leading to enhanced wavelength tunability and higher spectral selectivity. A key contribution of this study is the demonstration of a dual-parameter tuning mechanism that combines input optical intensity and angle of incidence, enabling dynamic compensation between intensity-induced redshift and angle-induced blueshift of the defect mode. This dual control provides improved flexibility compared to conventional single-parameter approaches. The proposed graphene-based structure offers promising potential for tunable photonic devices such as optical filters, all-optical switches, sensors, and optical limiters.</div></div>","PeriodicalId":19513,"journal":{"name":"Optik","volume":"347 ","pages":"Article 172670"},"PeriodicalIF":3.1,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-01-07DOI: 10.1016/j.ijleo.2026.172668
Rupesh Singh , Dilip Kumar Giri
The work is devoted to the antibunching and sub-Poissonian photon statistics in the degenerate frequency up-conversion (FUC) process using a short-time approximation in the Heisenberg picture. We analyse how pump photon numbers, interaction times, and coupling strengths affect nonclassicality, distinguishing between first- and second-order Hamiltonian interactions. Results show that first-order interactions lead to stronger nonclassical effects, though only second-order interactions enable antibunching in the harmonic mode due to higher-order pump contributions. Photon antibunching intensity increases with pump strength and shorter interaction times. In the first-order coupling interactions, the harmonic mode does not exhibit antibunching because a coherent or vacuum pump induces photon clustering. However, second-order interactions, where higher powers of the pump field contribute significantly, facilitate antibunching in the harmonic mode. Third-order antibunching exhibits the strongest nonclassical behaviour within the observed effects, followed by second- and first-order antibunching. It is more apparent that increased pump intensity and reduced interaction time both strengthen antibunching and sub-Poissonian photon statistics. While the pump mode exhibits clear antibunching, the harmonic mode displays milder nonclassicality. These results reveal the higher-order transitions of antibunching as an inherent quantum feature of light, valuable for quantum communication and single-photon sources with a probabilistic destination.
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