Search Results (95)

The photon spin Hall effect (PSHE) arises from the spin–orbit interaction of light. Metasurfaces enable precise control over the PSHE through their influence. Using electromagnetic simulations as its foundation, this work engineers a metal–insulator–metal (MIM) metasurface for generating vortex beams in the near-infrared band, targeting enhanced modulation of the PSHE. Electromagnetic simulations embed vanadium dioxide (VO₂)—a thermally responsive phase-change material—within the MIM metasurface architecture. Numerical evidence confirms that harnessing VO₂’s insulator–metal-transition-mediated optical switching dynamically tailors spin-dependent splitting in the illuminated MIM-VO₂ hybrid, thereby achieving a significant amplification of the PSHE displacement. Electromagnetic simulations determine the reflection coefficients for both VO₂ phase states in the MIM-VO₂ structure. Computed spin displacements under vortex beam incidence reveal that VO₂’s phase transition couples to the MIM’s top metal and dielectric layers, modifying reflection coefficients and producing phase-dependent PSHE displacements. The simulation results show that the displacement change of the PSHE before and after the phase transition of VO₂ reaches 954.7 µm, achieving a significant improvement compared with the traditional layered structure. The dynamic modulation mechanism of the PSHE based on the thermal–optical effect has been successfully verified. Full article

Millimeter-wave (mmWave) antennas and antenna arrays have gained significant attention due to their pivotal role in emerging wireless communication, sensing, and imaging technologies. With the rapid deployment of 5G and the transition toward 6G networks, the demand for compact, high-gain, and reconfigurable mmWave antennas has intensified. This article highlights recent advancements in mmWave antenna technologies, including hybrid beamforming using phased arrays, dynamic beam-steering enabled by liquid crystal and MEMS-based structures, and high-capacity MIMO architectures. We also examine the integration of metamaterials and metasurfaces for miniaturization and gain enhancement. Applications covered include wearable antennas with low-SAR textile substrates, conformal antennas for UAV-based mmWave relays, and high-resolution radar arrays for autonomous vehicles. The study further analyzes innovative fabrication methods such as inkjet and aerosol jet printing, micromachining, and laser direct structuring, along with advanced materials like Kapton, PDMS, and graphene. Numerical modeling techniques such as full-wave EM simulation and machine learning-based optimization are discussed alongside experimental validation approaches. Beyond communications, we assess mmWave systems for biomedical imaging, security screening, and industrial sensing. Key challenges addressed include efficiency degradation at high frequencies, interference mitigation in dense environments, and system-level integration. Finally, future directions, including AI-driven design automation, intelligent reconfigurable surfaces, and integration with quantum and terahertz technologies, are outlined. This comprehensive synthesis aims to serve as a valuable reference for advancing next-generation mmWave antenna systems. Full article

Terahertz (THz) biosensing faces critical challenges in balancing high sensitivity and broadband spectral coverage, particularly under miniaturized device constraints. Conventional quasi-bound states in the continuum (QBIC) metasurfaces achieve high quality factor (Q) but suffer from narrow bandwidth, while angle-scanning strategies for broadband detection require complex large-angle illumination. Here, we propose a symmetry-engineered, all-dielectric metasurface that leverages multipolar interference coupling to overcome this limitation. By introducing angular perturbation, the metasurface transforms the original magnetic dipole (MD)-dominated QBIC resonance into hybridized, multipolar modes. It arises from the interference coupling between MD, toroidal dipole (TD), and magnetic quadrupole (MQ). This mechanism induces dual counter-directional, frequency-shifted, resonance branches within angular variations below 16°, achieving simultaneous 0.42 THz broadband coverage and high Q of 499. Furthermore, a derived analytical model based on Maxwell equations and mode coupling theory rigorously validates the linear relationship between frequency splitting interval and incident angle with the Relative Root Mean Square Error (RRMSE) of 1.4% and the coefficient of determination ($R^2$) of 0.99. This work establishes a paradigm for miniaturized THz biosensors, advancing applications in practical molecular diagnostics and multi-analyte screening. Full article

Acoustic metasurfaces play a key role in building acoustics, noise control, and acoustic cloaking by regulating the acoustic wave scattering characteristics through subwavelength structures. The design of diffusely reflecting metasurfaces aims to achieve a uniform distribution of a scattered field, which is essentially a high-dimensional nonconvex optimization problem that needs to balance the computational efficiency in the synergistic optimization of the spatial arrangement of cells and the angular response. In traditional methods, a heuristic algorithm is prone to local optimization, and it is difficult to balance the global search and local adjustment. And full-wave simulation is time consuming and seriously restricts the design efficiency. Therefore, the hybrid tornado-gradient descent optimization algorithm (VDGD) is proposed in this paper. It uses a two-stage collaborative optimization approach to refine the reflection angle distribution of acoustic metasurfaces, thereby enhancing the uniformity of the diffuse acoustic field. The Tornado Optimization Algorithm (TOA) was initially employed to introduce global perturbations to the randomly initialized design. Local optimization can be avoided by gradually decreasing the perturbation magnitude, which reduces the standard deviation of the sound field from about 5.81 dB to about 4.07 dB. Then, the gradient descent is used for local fine adjustment to further reduce the standard deviation to about 1.91 dB. Experimental results show that the VDGD algorithm outperforms the seven classical and up-to-date optimization algorithms in improving scattering uniformity. This method achieves an effective balance between global search and local fine tuning, providing an efficient and flexible optimization strategy for metasurface design, which can bring application support for intelligent acoustic devices and sound field regulation. Full article

Quasibound states in the continuum (qBICs) have aroused much attention as a feasible stage to investigate optical strong coupling due to their extremely high-quality factors (Q-factors) and extraordinary electromagnetic field enhancement. However, current demonstrations of strong coupling based on qBICs have primarily focused on the visible spectral range, while research in the near-infrared (NIR) regime remains scarce. In this work, we design a nanograting metasurface supporting Friedrich–Wintgen bound states in the continuum (FW BICs). We demonstrate that FW BIC formation stems from destructive interference between Fabry–Pérot cavity modes and metal–dielectric hybrid guided-mode resonances. To investigate the qBIC–exciton coupling system, we simulated the interaction between MoTe₂ excitons and nanograting metasurfaces. A Rabi splitting of 55.4 meV was observed, which satisfies the strong coupling criterion. Furthermore, a chiral medium layer is modeled inside the nanograting metasurface by rewriting the weak expression and boundary conditions. A mode splitting of the qBIC–chiral medium system in the circular dichroism (CD) spectrum demonstrates that the chiral response successfully transferred from the chiral medium layer to the exciton–polaritons systems through strong coupling. In comparison to the existing studies, our work demonstrates a significantly larger CD signal under the same Pascal parameters and with a thinner chiral dielectric layer. Our work provides a new ideal platform for investigating the strong coupling based on quasibound states in the continuum, which exhibits promising applications in near-infrared chiral biomedical detection. Full article

Metasurfaces, as subwavelength planar structures, offer unprecedented electromagnetic wavefront manipulation capabilities. However, most existing focusing metasurfaces operate in a single polarization mode, support only one focusing function, or rely on complex multi-unit configurations, limiting their versatility in practical applications. This study proposes a dual-polarization multiplexed transmissive focusing metasurface operating at 5.8 GHz. Through theoretical analysis and full-wave simulations, the electromagnetic response of the metasurface unit is systematically investigated. To overcome the limitations of conventional transmissive units, an anisotropic low-profile unit is designed using a hybrid stacking strategy that combines dielectric substrates and an air layer, achieving a compact profile of only 0.16λ. This unit achieves 360° phase modulation with a transmission magnitude exceeding 0.85 while being lightweight and cost-effective. Based on the unit, three metasurface arrays are developed to achieve various focusing functions, including single-point offset focusing, dual-point focusing, and multi-focal energy-controlled focusing, offering over 15% operational bandwidth and maintaining satisfactory performance under a 25° oblique incidence, with respective efficiencies of 35.59%, 25.11%, and 33.42%. This work provides a novel solution for multifunctional focusing applications, expanding the potential of metasurfaces in wireless communication, wireless power transfer, and beyond. Full article

Metasurfaces (MSs) have emerged as a promising technology for optical system design. When combined with traditional refractive optics, MS-refractive hybrid lenses can enhance imaging performance, reduce optical aberrations, and introduce new functionalities such as polarization control. However, modeling these hybrid lenses requires advanced simulation techniques that usually go beyond conventional raytracing tools. This work presents a physical optics framework for modeling MS-refractive hybrid lenses. We introduce a ray-wave hybrid method that integrates multiple propagation techniques to account for vector wave propagation through various optical elements. At the center of the proposed framework is the Gaussian decomposition method for modeling beam propagation through refractive optics. Ray-path diffraction is automatically considered in this method, and complex input wavefront can be modeled as well. Several techniques are integrated to ensure accuracy in decomposing an incoming vector wave into Gaussian beamlets, such as adaptive consideration of local wavefront principal curvatures and best-fit beam width estimation from the local covariance matrix. To demonstrate the effectiveness of our method, we apply it to several hybrid lens designs, including polarization-sensitive MSs and aberration-correcting MSs integrated into complex optical systems. Full article

We propose a wide field-of-view (FOV) refractive and meta-optics hybrid imaging system designed for the mid-wave infrared spectrum (3–5 μm) to address the challenge of high-quality imaging in wide FOV applications. The system consists of only three refractive lenses and two metasurfaces (one functioning as a circular polarizer and the other as a phase element), with a total length of 29 mm. Through a detailed analysis of modulation transfer function curves and spot diagrams, the system achieves 178° FOV while maintaining exceptional imaging performance across a temperature range of −40 °C to 60 °C. The system demonstrates the potential for extending applications to other wavelengths and scenarios, thereby contributing to the advancement of high-performance compact optical systems. Full article

Recent advancements in metal/perovskite photodetectors have leveraged plasmonic effects to enhance the efficiency of photogenerated carrier separation. In this work, we present an innovative approach to designing heterostructure photodetectors that involved integrating a perovskite film with a plasmonic metasurface. Using finite-difference time-domain (FDTD) simulations, we investigated the formation of hybrid photonic–plasmonic modes and examined their quality factors in relation to loss mechanisms. Our results demonstrate that these hybrid modes facilitated strong light confinement within the perovskite layer, with significant intensity enhancement at the metal–perovskite interface—an ideal condition for efficient charge carrier generation. We also propose the use of low-bandgap perovskites for direct infrared passive detection and explore the potential of highly Stokes-shifted perovskites for active detection applications, including ultraviolet and X-ray radiation. Full article

Acquiring information about the surrounding environment is crucial for reconfigurable intelligent surfaces (RISs) to effectively manipulate radio wave propagation. This operation can be fully automated by incorporating an integrated sensing mechanism, leading to a hybrid configuration known as a hybrid reconfigurable intelligent surface (HRIS). Several HRIS geometries have been studied in previous works, with full-wave simulations used to showcase their sensing capabilities. However, these simulated models often fail to address the practical design challenges associated with HRISs. This paper presents an experimental proof-of-concept for an HRIS, focusing on the design considerations that have been neglected in simulations but are vital for experimental validation. The HRIS prototype comprises two types of elements: a conventional element designed for reconfigurable reflection and a hybrid one for sensing and reconfigurable reflection. The metasurface can carry out the required sensing operations by utilizing signals coupled to several hybrid elements. This paper outlines the design considerations necessary to create a practical HRIS configuration that can be fabricated using standard PCB technology. The sensing capabilities of the HRIS are demonstrated experimentally through angle of arrival (AoA) detection. The proposed HRIS has the potential to facilitate smart, autonomous wireless communication networks, wireless power transfer, and sensing systems. Full article

Quarter-wave plate (QWP) metasurfaces provide a novel approach for generating three-dimensional (3D) hybrid-order Poincaré sphere (HyOPS) beams and enabling longitudinal polarization modulation, owing to their unique spin-decoupling properties. In this work, we designed a set of QWP meta-atom metasurfaces that generate 3D HyOPS beams with continuously varying polarization states along the propagation direction. The third-, fourth- and fifth-order HyOPS beams are generated by three metasurface devices, respectively. The HyOPS beams exhibit a focal depth of 30 μm, a stable longitudinal propagation, and a continuously evolving polarization state. Notably, complete polarization evolution along the equator of the HyOPS occurs within a depth of 20 μm. Numerical calculations in MATLAB R2022b validated the feasibility of the designed QWP metasurfaces. The finite-difference time-domain (FDTD) simulations further confirmed the stable propagation and continuous polarization evolution of the longitudinal light field. Additionally, the concentric arrangement of the QWP meta-atoms on the metasurface effectively mitigates scattering crosstalk caused by abrupt edge phase variations. This work offers new insights into the generation and control of HyOPS light fields and contributes significantly to the development of miniaturized, functionally integrated high-performance nanophotonics. Full article

The precise and deterministic integration of fluorescent emitters with photonic nanostructures is an important challenge in nanophotonics and key to the realization of hybrid photonic systems, supporting effects such as emission enhancement, directional emission, and strong coupling. Such integration typically requires the definition or immobilization of the emitters at defined positions with nanoscale precision. While various methods were already developed for creating localized emitters, in this work we present a new method for the deterministic fabrication of fluorescent nanostructures featuring well-defined optical transitions; it works with a minimal amount of steps and is scalable. Specifically, electron-beam lithography is used to directly pattern a mixture of the negative-tone electron-beam resist with the europium complex Eu(TTA)₃, which exhibits both electric and magnetic dipolar transitions. Crucially, the lithography process enables precise control over the shape and position of the resulting fluorescent structures with a feature size of approx. 100 $\mathrm{n}$$\mathrm{m}$. We demonstrate that the Eu(TTA)₃ remains fluorescent after exposure, confirming that the electron beam does not alter the structure the optical transitions. This work supports the experimental study of local density of optical states in nanophotonics. It also expands the knowledge base of fluorescent polymer materials, which can have applications in polymer-based photonic devices. Altogether, the presented fabrication method opens the door for the realization of hybrid nanophotonic systems incorporating fluorescent emitters for light-emitting dielectric metasurfaces. Full article

Photonic biosensors based on bound states in the continuum (BIC) resonant modes exhibit a transformative potential for high-sensitivity, label-free detection across various diagnostic applications. BIC-enabled metasurfaces, utilizing dielectric, plasmonic, and hybrid structures, achieve ultra-high Q-factors and amplify target molecule interactions on functionalized sensor surfaces. These unique properties result in increased refractive index sensitivity and low detection limits, essential for monitoring biomolecules in clinical diagnostics, environmental analysis, and food safety. Recent advancements in BIC-enabled metasurfaces have demonstrated ultra-low detection limits in the zeptomolar range, making these devices highly promising for real-world applications. This review paper critically discusses the design principles of BIC-based biosensors, emphasizing key factors such as material selection, structural asymmetry, and functionalization strategies that enhance both sensitivity and specificity. Additionally, recent advancements in fabrication techniques that enable precise BIC control with scalable approaches for practical biosensing applications are examined. Case studies demonstrate the effectiveness of BIC metasurfaces for real-time, low-concentration detection, highlighting their versatility and adaptability. Finally, the review discusses future challenges and opportunities, such as integration with microfluidics for point-of-care testing and multiplexed sensing, underscoring the potential of BIC-based platforms to revolutionize the field of biosensing. Full article

The Sweatt model has been extensively used to design optical systems containing diffractive optical elements (DOEs) because it captures the dispersive characteristics of DOEs. We introduce a new dispersive Sweatt model (DSM) that can describe meta-atom (MA) dispersion, which has material and geometric contributions in addition to diffraction. It uses a wavelength-dependent scalar coefficient to modify the diffractive dispersion and describe the dispersion of a given MA basis. This provides a robust framework to design systems containing metasurface (MS) elements while including their unique dispersive properties in the design optimization. Importantly, the DSM is based on ray optics and enables the design of MS-containing systems using conventional optical design software such as Zemax and Code V. We use the DSM to demonstrate the design of a hybrid refractive/MS achromatic doublet for the midwave infrared (MWIR) band. The design example includes multiple wavelengths and field angles during optimization and demonstrates excellent agreement between the DSM and real hybrid lens performance modeled using wave optics. We discuss the limits of the DSM and present a simple model to predict performance limits due to phase mismatch at Fresnel zone boundaries. Full article

In this study, a hybrid energy harvesting system based on a conventional solar cell combined with 3D-printed metasurface units is studied. Millimeter-scale metasurface units were fabricated via the stereolithography technique, and then they were covered with conductive silver paint, in order to achieve high electric conductivity. The performance of single, as well as two-unit metasurface harvesters, was thoroughly investigated. It was found that both of them produced voltage, which peaks at their resonance frequency, demonstrating efficient energy harvesting behavior in the microwave regime. Then, the metasurface units were connected with a commercially available photovoltaic panel and the performance of the hybrid system was examined under different environmental conditions, modifying the light intensity (i.e., light, dark and shadow). It was shown that the proposed hybrid harvesting system produces a sizable voltage output, which persists, even in the case when one of the components does not contribute. Furthermore, the performance of the hybrid harvester is found to be adequate enough, although optimization of the harvesting circuit is required in order to achieve high efficiency levels. All in all, the presented experimental evidence clearly indicates the realization of a rather promising hybrid energy harvesting system, exploiting two distinct ambient energy sources, namely light and microwaves. Full article