Search Results (31)

The fast growth of smart city systems requires sensing and intelligence systems that are dynamic, power-efficient, and have capabilities of real-time decision-making. The traditional IoT-based smart city systems are subject to constraints like nonflexible sensing architectures, high energy use, and high-latency because of processing on clouds. To solve these problems, in this paper, a reconfigurable metasurface-based Artificial Intelligence of Things (AIoT) architecture of smart cities is proposed. The proposed system incorporates programmable electromagnetic metasurface-based sensing, edge-level Artificial Intelligence, and AIoT gateways to implement ultra-sensitive sensing, low-latency analytics, and effective resource utilization. A computer algorithm with a hybrid realization between metasurface physics and neural network-based learning can be used to improve the accuracy and flexibility of sensing. The experimental analysis with publicly available data of a smart city proves that the proposed framework can attain an accuracy of sensing in the range of 92% and 97%, by far surpassing traditional IoT sensors, with 78% and 83% as the accuracy limits. Moreover, the suggested system shortens end-to-end latency to as low as 3645 ms, as compared to 8490 ms, and also reduces the power usage. The improved sensing efficiency, which is defined as the ratio of power consumption to accuracy, is obtained in all test conditions. These findings validate that the suggested AIoT framework, powered by the metasurface, can be used to offer a scalable and low-latency solution that uses less energy when it is deployed in applications linked to smart cities of the next generation. Full article

A central challenge in reconfigurable photonics based on quasi bound states in the continuum (quasi-BICs) is to move beyond binary switching toward multistate and polarization-aware programmability. Here we propose a dual-phase-change material (PCM) metasurface that enables four-state nonvolatile switching and polarization-divergent dispersion rewriting within a single unit cell. Two independently switchable PCM layers provide four addressable configurations (0-0, 0-1, 1-0, 1-1) at a fixed geometry, allowing the resonance landscape to be reprogrammed through complex-index rewriting without structural modification. Angle-resolved transmission maps reveal fundamentally different evolution pathways for orthogonal polarizations. For p polarization, the quasi-BIC exhibits strong state sensitivity with dispersion reshaping and multi-branch features near normal incidence; the resonance red-shifts from ~1331 nm to ~1355 nm while the quality factor decreases from ~6.7 × 10⁴ to ~4.0 × 10⁴. In contrast, for s polarization, a single weakly dispersive branch translates coherently across states, producing a much larger shift from ~1635 nm to ~1790 nm while the quality factor increases from ~9.0 × 10³ to ~1.8 × 10⁴. The opposite quality-factor trajectories, together with the polarization-contrasting tuning ranges, demonstrate that dual-PCM programming reconfigures polarization-selective radiative coupling rather than imposing a uniform resonance shift. This compact two-bit metasurface platform provides multistate, high-Q control with active dispersion engineering, enabling polarization-multiplexed reconfigurable filters, state-addressable sensors, and other programmable photonic devices. Full article

Plasmonics and metasurfaces (MSs) have emerged as two of the most influential platforms for manipulating light at the nanoscale, each offering complementary strengths that challenge the limits of conventional optical design. Plasmonics enables extreme subwavelength field confinement, ultrafast light–matter interaction, and strong optical nonlinearities, while MSs provide versatile and compact control over phase, amplitude, polarization, and dispersion through planar, nanostructured interfaces. Recent advances in materials, nanofabrication, and device engineering are increasingly enabling these technologies to be combined within unified planar and hybrid optical platforms. This review surveys the physical principles, material strategies, and device architectures that underpin plasmonic, MS, and hybrid plasmonic–dielectric systems, with an emphasis on interface-mediated optical functionality rather than long-range guided-wave propagation. Key developments in modulators, detectors, nanolasers, metalenses, beam steering devices, and programmable optical surfaces are discussed, highlighting how hybrid designs can leverage strong field localization alongside low-loss wavefront control. System-level challenges including optical loss, thermal management, dispersion engineering, and large-area fabrication are critically examined. Looking forward, plasmonic and MS technologies are poised to define a new generation of flat, multifunctional, and programmable optical systems. Applications spanning imaging, sensing, communications, augmented and virtual reality, and optical information processing illustrate the transformative potential of these platforms. By consolidating recent progress and outlining future directions, this review provides a coherent perspective on how plasmonics and MSs are reshaping the design space of next-generation planar optical hardware. Full article

The ability to independently manipulate the amplitude, phase, and polarization state of light constitutes a central problem in the advancement of integrated photonic devices. In this paper, we propose three multichannel wavelength-selective dielectric metasurfaces that utilize complex amplitude modulation to achieve precise and flexible simultaneous control over the spatial position, wavelength, and amplitude of multichannel optical fields. First, the designed metasurface simultaneously generates three pairs of independent foci with uniform intensity at wavelengths of 444 nm, 517 nm, and 700 nm, demonstrating foundational multi-wavelength control. Moreover, the second metasurface achieves complex amplitude distributions with different amplitude ratios through joint modulation of amplitude and phase, providing a solution for programmable adjustment of the relative intensity between foci, whereas the third metasurface offers high design freedom, capable of generating an arbitrary number of foci with customized positions and amplitude ratios across multiple wavelength bands, meeting the requirements for complex optical field construction. The findings suggest that such complex amplitude metasurfaces have broad application prospects in fields such as optical imaging, particle manipulation, and high-density information multiplexing. Full article

Optical skyrmions, as topologically protected quasiparticles, hold great promise for on-chip photonic technologies. However, achieving programmable control over their properties through subtle structural changes remains challenging. This study introduces a minimal perturbation engineering strategy on a plasmonic metasurface. By applying controlled geometric perturbations (either continuous shortening or discrete segmentation) to a single edge of a hexagonal groove structure, combined with incident phase perturbations, we systematically manipulate the evolution of the skyrmion texture. These minimal perturbations induce reproducible shifts in the skyrmions’ center intensity and peak position, yielding up to ~32% center suppression, while the global topological charge remains conserved. This “geometry × phase” dual-perturbation approach provides a straightforward and efficient approach for engineering programmable topological light fields on a chip, with promising applications in integrated photonic devices. Full article

This study presents a reconfigurable planar photonic device capable of dynamically switching between optical filter and absorber functionalities by exploiting the phase transition properties of GeTe, a chalcogenide phase-change material. The device adopts a Metal–Dielectric–PCM architecture composed of silver (Ag), silicon dioxide (SiO₂), and GeTe layers, each playing a distinct role: the silver layer governs the transmission and absorption efficiency, the SiO₂ layer controls the resonance conditions, and the GeTe layer determines the device’s scattering behavior via its tunable optical losses. Numerical simulations revealed that the structure enables high RGB transmission in the amorphous state and broadband absorption in the crystalline state. By adjusting geometric parameters—especially the metallic thickness—the device exhibits finely tunable spectral responses under varying polarizations and incidence angles. These findings highlight the synergistic interplay between material functionality and layer configuration, positioning this platform as a compact and energy-efficient solution for applications in tunable photonics, optical sensing, and programmable metasurfaces. Full article

Airy beams exhibit enormous application potential in the field of optics and microwave owing to their unique self-bending, self-accelerating, and non-diffracting characteristics. In this paper, the Airy beams are dynamically generated and manipulated in both reflection and transmission spaces utilizing a full space programmable metasurface, which can achieve an approximately 360° phase coverage in the reflection space and a nearly 180° phase coverage in the transmission space in the operating frequency band from 6 GHz to 7 GHz. The direct current (DC) bias voltage is applied to the varactor diodes integrated on the metasurface by precise control of the external feeding system, allowing dynamic generation and regulation of Airy beams. Numerical simulations and experimental measurements are performed at 6.5 GHz. The Airy beams with parameters a = 56 and 61 are generated in the transmission space, while the Airy beams with parameters a = 71 and 81 are achieved in the reflection space. The parabolic propagation trajectory of the main beams and acceleration in the transverse planes can be observed. The good agreement between the simulated and measured results demonstrates that the metasurface can dynamically generate and manipulate the Airy beams in full space. The suggested Airy beam manipulation system has a wide range of applications, including optical particle manipulation, imaging, and difficult terrain exploration. Full article

Nanophotonics, the study of light–matter interactions at the nanometer scale, has emerged as a transformative field that bridges photonics and nanotechnology. Using engineered nanomaterials—including plasmonic metals, high-index dielectrics, two-dimensional (2D) materials, and hybrid systems—nanophotonics enables light manipulation beyond the diffraction limit, unlocking novel applications in sensing, imaging, and quantum technologies. This review provides a comprehensive overview of recent advances (post-2020) in nanophotonic materials, fabrication methods, and their cutting-edge applications. We first discuss the fundamental principles governing nanophotonic phenomena, such as localized surface plasmon resonances (LSPRs), Mie resonances, and exciton–polariton coupling, highlighting their roles in enhancing light–matter interactions. Next, we examine state-of-the-art fabrication techniques, including top-down (e.g., electron beam lithography and nanoimprinting) and bottom-up (e.g., chemical vapor deposition and colloidal synthesis) approaches, as well as hybrid strategies that combine scalability with nanoscale precision. We then explore emerging applications across diverse domains: quantum photonics (single-photon sources, entangled light generation), biosensing (ultrasensitive detection of viruses and biomarkers), nonlinear optics (high-harmonic generation and wave mixing), and integrated photonic circuits. Special attention is given to active and tunable nanophotonic systems, such as reconfigurable metasurfaces and hybrid graphene–dielectric devices. Despite rapid progress, challenges remain, including optical losses, thermal management, and scalable integration. We conclude by outlining future directions, such as machine learning-assisted design, programmable photonics, and quantum-enhanced sensing, and offering insights into the next generation of nanophotonic technologies. This review serves as a timely resource for researchers in photonics, materials science, and nanotechnology. Full article

Unmanned Aerial Vehicles (UAVs), commonly known as drones, are becoming increasingly important in multiple areas and various applications, including communication, detection, and monitoring. This review paper examines the development of antennas for UAVs, with a particular focus on miniaturization techniques, polarization strategies, and beamforming solutions. It explores both structural and material-based methods, such as meander lines, slots, high-dielectric substrates, and metasurfaces, which aim to make the antenna more compact without compromising performance. Different antenna types including dipole, monopole, horn, vivaldi, and microstrip patch are explored to identify solutions that meet performance standards while respecting UAV constraints. In terms of polarization strategies, these are often implemented in the feeding network to achieve linear or circular polarization, and beamforming techniques like beam-steering and beam-switching enhance communication efficiency by improving signal directionality. Future research should focus on more lightweight, structurally integrated, and reconfigurable apertures that push miniaturization through conformal substrates and programmable metasurfaces, extending efficient operation from 5/6 GHz into the sub-THz regime and supporting agile beamforming for dense UAV swarms. Full article

Sixth-generation (6G) wireless networks have the potential to transform global connectivity by supporting ultra-high data rates, ultra-reliable low latency communication (uRLLC), and intelligent, adaptive networking. To realize this vision, 6G must incorporate groundbreaking technologies that enhance network efficiency, spectral utilization, and dynamic adaptability. Among them, unmanned aerial vehicles (UAVs), terahertz (THz) communication, and intelligent reconfigurable surfaces (IRSs) are three major enablers in redefining the architecture and performance of next-generation wireless systems. This survey provides a comprehensive review of these transformative technologies, exploring their potential, design challenges, and integration into future 6G ecosystems. UAV-based communication provides flexible, on-demand communication in remote, harsh areas and is a vital solution for disasters, self-driving, and industrial automation. THz communication taking place in the 0.1–10 THz band reveals ultra-high bandwidth capable of a data rate of multi-gigabits per second and can avoid spectrum bottlenecks in conventional bands. IRS technology based on programmable metasurface allows real-time wavefront control, maximizing signal propagation and spectral/energy efficiency in complex settings. The work provides architectural evolution, active current research trends, and practical issues in applying these technologies, including their potential contribution to the creation of intelligent, ultra-connected 6G networks. In addition, it presents open research questions, possible answers, and future directions and provides information for academia, industry, and policymakers. Full article

This work reports the design of a 1x2 photonic digital switch controlled by an electrically induced metasurface, configurated by a rectangular array of points where the refractive index is locally changed through the application of an external bias. The device is simulated using the Beam Propagation Method (BPM) and Finite Difference Time Domain (FDTD) algorithms and the structure under evaluation is an amorphous silicon 1x2 multimode interference (MMI), joined to an arrayed Metal Oxide Semiconductor (MOS) structure Al/SiNx/a-Si:H/ITO to be used in active-matrix pixel fashion to control the output of the switch. MMI couplers, based on self-imaging multimode waveguides, are very compact integrated optical components that can perform many different splitting and recombining functions. The input–output model has been defined using a machine learning approach; a high number of images have been generated through simulations, based on the beam propagation algorithm, obtaining a large dataset for an MMI structure under different activation maps of the MOS pixels. This dataset has been used for training and testing of a machine learning algorithm for the classification of the MMI configuration in terms of binary digital output for a 1x2 switch. Also, a statistical analysis has been produced, targeting the definition of the most incident-activated pixel for each switch operation. An optimal configuration is proposed and applied to demonstrate the operation of a digital cascaded switch. This proof of concept paves the way to a more complex device class, supporting the recent advances in programmable photonic integrated circuits. Full article

Artificial metasurfaces can rapidly modulate their electromagnetic scattering properties and the characteristics of echo signals, which can lead to different imaging features in synthetic aperture radar (SAR) imaging results. Based on this, for the first time, this paper proposes an approach for SAR feature reconfiguring based on periodic phase modulation with inter-pulse time bias. Considering the position and energy requirements of the expected reconfigured imaging target, this approach optimizes the metasurface modulation parameters via a dual algorithm collaborative optimization system, i.e., a modulation parameter generation algorithm (MPGA) and a parameter mapping matching algorithm (PMMA). Time-modulated metasurface targets can reconfigure imaging features of different targets at SAR reconnaissance moments under the guidance of optimized modulation parameters obtained using this approach. Compared with the previous single-point target research on the combination of SAR and metasurfaces, this method is expanded to include the combined analysis of multi-point targets and the reconfigurability of SAR features. Experiments have proved that the programmable reconfigurability of different target features (such as passenger plane targets and truck targets) can be achieved in SAR imaging results through dynamic adjustment of the modulation parameter set. The reconfigured imaging features maintain geometric consistency within the resolution error range, and the size and position of the target can be set as required. Full article

Intelligent Reflecting Surfaces (IRSs) enable us to have a reconfigurable reflecting surface that can efficiently deflect the transmitted signal toward the receiver. The initial step in the IRS usually involves estimating the channel between a fixed transmitter and a stationary receiver. After estimating the channel, the problem of finding the most optimal IRS configuration is non-convex, and involves a huge search in the solution space. In this work, we propose a novel and customized technique which efficiently estimates the channel and configures the IRS with fixed transmit power, restricting the IRS coefficients to $\{1,-1\}$. The results from our approach are numerically compared with existing optimization techniques.The key features of the linear system model under consideration include a Reconfigurable Intelligent Surface (RIS) setup consisting of 4096 RIS elements arranged in a 64 × 64 element array; the distance from RIS to the access point measures 107 m. NLOS users are located around 40 m away from the RIS element and 100 m from the access point. The estimated variance of noise ${\mathcal{N}}_{\mathbb{C}}$ is 3.1614 $\times {10}^{-20}$. The proposed algorithm provides an overall data rate of 126.89 (MBits/s) for Line of Sight and 66.093 (MBits/s) for Non Line of Sight (NLOS) wireless communication. Full article

Metasurfaces can realize the flexible manipulation of electromagnetic waves, which have the advantages of a low profile and low loss. In particular, the coding metasurface can flexibly manipulate electromagnetic waves through controllable sequence encoding of the coding units to achieve different functions. In this paper, a three-layer active coding metasurface is designed based on vanadium dioxide ($V{O}_2$), which has an excellent phase transition. For the designed unit cell, the top patterned layer is composed of two split square resonant rings (SSRRs), whose gaps are in opposite directions, and each SSRR is composed of gold and $V{O}_2$. When $V{O}_2$ changes from the dielectric state to the metal state, the resonant mode changes from microstrip resonance to LC resonance, correspondingly. According to the Pancharatnam-Berry (P-B) phase, the designed metasurface can actively control terahertz circularly polarized waves in the near field. The metasurface can manipulate the order of the generated orbital angular momentum (OAM) beams: when the dielectric $V{O}_2$ changes to metal $V{O}_2$, the order l of the OAM beams generated by the metasurface changes from −1 to −2, and the purity of the generated OAM beams is relatively high. It is expected to have important application values in terahertz wireless communication, radar, and other fields. Full article

Programmable metasurfaces are two-dimensional electromagnetic structures characterized by a low profile, conformability, and the ability to flexibly manipulate the amplitude and phase of electromagnetic waves. For high-quality beam scanning with the metasurface, it is essential that the metasurface possesses high-precision phase response quantization characteristics. This paper constructs a reflection-type metasurface unit cell featuring four P-I-N diodes and six operating states. To address the unit cell’s complexity and optimization challenges, we developed an automatic optimization algorithm, derived from the genetic optimization algorithm, for the metasurface unit cell. This algorithm was used to optimize a six-phase reflective 2.5 bit programmable metasurface cell operating at 5 GHz. The unit cell’s prototype was fabricated and measured to verify the design. Additionally, a metasurface comprising 16 × 16 unit cells was designed and simulated. The results highlight the metasurface unit cell’s excellent phase response quantization characteristics, and investigate the impact of quantization accuracy on beam scanning. Full article