Manipulation Of Electromagnetic Waves Research Articles

Wide-angle reflection control with a reflective digital coding metasurface for 5G communication systems

Abstract Metasurfaces have attracted widespread attention in recent years due to their powerful electromagnetic wave manipulation capabilities. This paper proposes and validates a single-polarized, angle-adjustable reflective digital coding metasurface. Each unit cell achieves independent reflection phase control by loading a PIN diode for on-off switching. The unit’s design and coding scheme are carefully optimized to ensure the performance of the proposed reconfigurable metasurface. As a validation, a prototype consisting of 16×16 elements is fabricated and measured, with a control signal provided by a field-programmable gate array controller. Experimental results demonstrate angle control of up to ±60° in the frequency range of 3.4 GHz–3.6 GHz, a peak gain of 24.9 dBi in a single channel, and gain exceeding 10 dBi across a 200 MHz operational bandwidth. Furthermore, the performance is validated in a communication system, yielding positive results. The proposed reflective digital coding metasurface contributes to the advancement of reconfigurable intelligent surfaces and holds promise for widespread adoption in various communication scenarios.

Terahertz Metasurfaces for Polarization Manipulation and Detection: Principles and Emerging Applications

AbstractTerahertz frequencies locating between microwave and infrared regions can record and process optical information for next‐generation information technology such as 6G communication. Metasurfaces, as emerging planar optical components built with micro‐ or nanostructures, enable precise control, and manipulation of electromagnetic waves from near fields to far fields. These subwavelength artificial structures can be engineered to exhibit specific polarization responses, thus holding significant potential for applications in polarization detection. In the terahertz (THz) region, polarization information is crucial for identifying and analyzing the properties of materials in the terahertz. In this review, we focus on recent advances in terahertz metasurfaces for polarization manipulation and detection, including principles and emerging applications. New polarization detection methods such as polarization state conversion, polarization‐selective absorption, polarization‐selective focusing, and vector beam construction are discussed. Finally, it is concluded with a few perspectives on emerging trends and existing challenges in the fields of terahertz polarization manipulation and detection.

Dynamic near-field and far-field radiation manipulation using a reprogrammable guided-wave-excited metasurface

The dynamic and integrated control of near- and far-field electromagnetic waves is essential for advancing emerging intelligent information technology. Metasurfaces, distinguished by their low-profile design, cost-effectiveness, and ease of fabrication, have successfully revolutionized various electromagnetic functions. However, current research on the dynamic integrated manipulation of near-field and far-field electromagnetic waves using a single metasurface remains relatively constrained, due to the complexity of element-level control, restricted dynamic tuning range, and tuning speed. Herein, we propose an element-level controlled, versatile, compact, and broadband platform allowing for the real-time electronic reconstruction of desired near/far-field electromagnetic wavefronts. This concept is achieved by precisely regulating the 1-bit amplitude coding pattern across a guided-wave-excited metasurface aperture loaded with PIN diodes, following our binary-amplitude holographic theory and modified Gerchberg–Saxton (G–S) algorithm. Consistent findings across calculations, simulations, and experiments highlight the metasurface’s robust performance in 2D beam scanning, frequency scanning, dynamic focusing lens, dynamic holography display, and 3D multiplexing holography, even under 1-bit control. This simplified and innovative metasurface architecture holds the promise of substantially propelling forthcoming investigations and applications of highly integrated, multifunctional, and intelligent platforms.

Engineering transmitted light speckle statistics with field-tunable magnetic nanofluid scatterers

The active manipulation of electromagnetic wave scattering cross-sections within disordered media is crucial for understanding mesoscopic physics. An adaptable strategy for exploring the parameter space in order to control the scattering cross-section of such systems involves employing external field-tunable disorder. In this study, we utilize magnetic nanofluid as an in-situ tunable scattering medium, whose scattering parameters like scatterer number, density, size, and shape can be adjusted by an external magnetic field which is administered either constantly or with varying ramp rates. Our study on the transmitted light and the associated speckle statistics reveals intriguing behavior in response to changes in the strength and duration of the applied magnetic field. We observe that this tunable system remains within the weak scattering regime across various scattering scenarios: Rayleigh (for scatterer sizes smaller than the light wavelength, λ), Mie (when scatterer size approaches λ), and Geometric (for scatterer sizes exceeding λ) under both constant and ramped magnetic field application. Further, the transmitted speckle patterns deviate from Rayleigh behavior, with speckle contrast values increasing over time until it reaches a saturation point. However, the speckle patterns display intriguing dynamics with faster ramp rates resulting in larger speckle contrast values. This phenomenon arises from the inability of equilibrium field-induced structures to form rapidly under faster ramp rates, leading to a broader size distribution of scatterers and consequently a wider range of phase differences among scattered light components. Our study illuminates the dynamic behavior of wave transport through a tunable disordered media and underscores the potential of magnetic nanofluid as a versatile tool for controlling mesoscopic transport.

Unidirectional guided-wave-driven metasurfaces for arbitrary wavefront control

Metasurfaces are capable of fully reshaping the wavefronts of incident beams in desired manners. However, the requirement for external light excitation and the resonant nature of their meta-atoms, make challenging their on-chip integration. Here, we introduce the concept and design of a fresh class of metasurfaces, driven by unidirectional guided waves, capable of arbitrary wavefront control based on the unique dispersion properties of unidirectional guided waves rather than resonant meta-atoms. Upon experimentally demonstrating the feasibility of our designs in the microwave regime, we numerically validate the introduced principle through the design of several microwave meta-devices using metal-air-gyromagnetic unidirectional surface magneto-plasmons, agilely converting unidirectional guided modes into the wavefronts of 3D Bessel beams, focused waves, and controllable vortex beams. We, further, numerically demonstrate sub-diffraction focusing, which is beyond the capability of conventional metasurfaces. Our unfamiliar yet practical designs may enable full, broadband manipulation of electromagnetic waves on deep subwavelength scales.

High-speed terahertz communication with graphene-based time-modulated low-bit phase coding metasurfaces: A novel architecture for enhanced performance

Coding metasurfaces have revolutionized electromagnetic device development by enabling precise electromagnetic wave manipulation. While spatial phase modulation alone offers significant capabilities, its limitations to comprehensive control and optimal functionality are evident. As a result of recent advancements, joint amplitude-phase coding approaches have been explored using different techniques in order to enhance performance. However, such methods often result in complex structures due to the combining of various modulation techniques within meta-atoms. Addressing this challenge, this paper proposes a novel architecture for terahertz (THz) communication utilizing low-bit coding metasurfaces featuring simplified meta-atoms. Our approach introduces a coding unit cell based on graphene, combined with time-modulated coding, to enable phase and amplitude control for different harmonics. As a proof-of-concept application, we demonstrate the effectiveness of our technique in multimode vortex communication. Moreover, we show secure hologram communication by using our proposed design within the THz frequency regime. By enhancing wavefront shaping flexibility through a straightforward approach, this work lays the foundation for next-generation devices, particularly in high-speed macroscale and nanoscale communication networks.

Ultrathin ring-shaped metasurface for a multiview 3D display

The development of glasses-free 3D multiview displays has opened up new avenues for experiencing 3D displays. Multiview technologies have the advantages of visual discomfort alleviation, smooth motion parallax, full-color display, and broad depth of focus. However, their intended uses are impeded due to the versatility of designing ultrathin display systems freely by using metasurface technology. This paper presents a technique for creating an ultrathin ring-shaped metasurface for a multiview display system with a thickness of 2 µm. The proposed multiview 3D display system generates eight views. Numerical simulations are used to confirm the efficacy of the suggested strategy, and the results demonstrate the attainment of a high-quality multiview 3D display. The proposed work demonstrates the potential applications of the metasurface in multiview display systems for electromagnetic wave manipulation in future 3D TVs, imaging, integrated optics, and next-generation compact displays.

A Dual-Polarization Programmable Metasurface for Green and Secure Wireless Communication.

Dual-polarization programmable metasurfaces can flexibly manipulate electromagnetic (EM) waves while providing approximately twice the information capacity. Therefore, they hold significant applications in next-generation communication systems. However, there are three challenges associated with the existing dual-polarization programmable metasurfaces. This article aims to propose a novel design to address them. First, the design overcomes the challenge of element- and polarization-independent controls, enabling more powerful manipulations of EM waves. Second, by using more energy-efficient tunable components and reducing their number, the design can be nearly passive (maximum power consumption of 27.7mW), leading to a significant decrease in the cost and power consumption of the system (at least two orders of magnitude lower than the power consumption of conventional programmable metasurfaces). Third, the design can operate in a broad bandwidth, which is attractive for practical engineering applications. Both the element and array of the metasurface are meticulously designed, and their performance has been carefully studied. The experiments demonstrate that 2D wide-angle beam scanning can be realized. Moreover, secure communication based on directional information modulation can be implemented by exploiting the metasurface and an efficient discrete optimization algorithm, showing its programmable, multiplexing, broadband, green, and secure features.

A Terahertz Programmable Digital Metasurface Based on Vanadium Dioxide

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 (VO2), 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 VO2. When VO2 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 VO2 changes to metal VO2, 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.

Miura Origami‐Inspired Reconfigurable Phase Gradient Metasurface for Linearly and Circularly Polarized Differential Modulation

Miura origami's reconfigurable characteristic and structural asymmetry, combined with electromagnetic (EM) wave manipulation, crashed a unique spark. However, the complexity of the three‐dimensional (3D) origami structure after folding makes it challenging to study the phase regulation mechanism. Here, we propose a reconfigurable phase gradient metasurface based on Miura origami and derive the underlying mechanism of phase modulation in detail under linearly and circularly polarized (LP and CP) incidence. We adopt the one‐dimensional (1D) gradient design along the x direction to verify the idea. The phase calculation formulas are given under LP and CP incidence through the Jones matrix's derivation. The beam deflector angles corresponding to LP and CP waves are identical in the planar state. As the folding angle increases, the phase evolution rules corresponding to the LP and CP waves are discrepant, leading to differential beam steering. Finally, the origami sample is processed for verification, and the experimental data are consistent with the simulation and theoretically calculated values. We believe this work can help analyze the EM behavior of complex 3D origami structures and lay a foundation for designing a multifunctional EM origami metasurface.

Huygens’ metasurface: From anomalous refraction to reflection

Huygens' metasurfaces (HMS) without any reflection or transmission are widely studied due to the high-efficiency manipulation of electromagnetic waves. In this work, three-layered metallic Huygens' metasurfaces are proposed and the geometry-dependences of anomalous refraction and reflection are investigated. The surface impedance and admittance are independently tailored by changing the length of metallic resonators, which is dictated by the introduction of the intermediate layer. Huygens’ metasurfaces can be geometrically engineered to realize anomalous refraction with an efficiency of 62% and anomalous reflection with an efficiency of 60%, respectively. It is anticipated that the proposed metasurface with tunable materials could achieve reconfigurable terahertz devices.

High‐Speed Wide‐Angle Sensing and Imaging by WideBand Metasurfaces with Joint Frequency, Polarization, and Spatial Diversities

AbstractHigh‐speed wide‐angle radio detection is crucial for intelligent wireless systems, autonomous vehicles, rescue operations in urgent situations, and security in various fields. This can be achieved through diverse controls of electromagnetic waves. Currently, multidimensional manipulations of electromagnetic waves are determined by dynamic antennas like phased arrays, mechanical beam‐steering radars, and programmable metasurface imagers. However, these methods face challenges in achieving rapid responses and large data collection intervals for high‐speed sensing and imaging, due to limitations in the speedy explication of analog‐to‐digital (AD) converters, electronic switches, phase shifters, and stepped motors for radiation beam reconfigurations. To address these challenges, advanced microwave‐to‐millimeter‐wave metasurfaces are introduced, designed to offer joint frequency, polarization, and spatial diversities. The metasurface with a disordered atom permutation enables wide‐angle sensing for accurate trajectory tracking of moving objects. On the other hand, a dispersion‐engineered atom arrangement allows the metasurfaces to facilitate wide‐angle through‐wall imaging, effective in detecting objects of varied shapes and positions. The experiments reveal that these metasurfaces can reconstruct objects at 100 frames per second (fps) from a single‐shot measurement, allowing 0.3x speed playback for detailed analysis. This demonstrates their potential in high‐speed sensing and imaging. Such a breakthrough is pivotal in unveiling new modalities and expanding possibilities in real‐time radio applications, including smart transportation, all‐condition surveillance, perspective radio, and integrated sensing and communication (ISAC) systems, especially relevant to technologies of 6G and beyond.

Review on the Scientific and Technological Breakthroughs in Thermal Emission Engineering.

The emission of thermal radiation is a physical process of fundamental and technological interest. From different approaches, thermal radiation can be regarded as one of the basic mechanisms of heat transfer, as a fundamental quantum phenomenon of photon production, or as the propagation of electromagnetic waves. However, unlike light emanating from conventional photonic sources, such as lasers or antennas, thermal radiation is characterized for being broadband, omnidirectional, and unpolarized. Due to these features, ultimately tied to its inherently incoherent nature, taming thermal radiation constitutes a challenging issue. Latest advances in the field of nanophotonics have led to a whole set of artificial platforms, ranging from spatially structured materials and, much more recently, to time-modulated media, offering promising avenues for enhancing the control and manipulation of electromagnetic waves, from far- to near-field regimes. Given the ongoing parallelism between the fields of nanophotonics and thermal emission, these recent developments have been harnessed to deal with radiative thermal processes, thereby forming the current basis of thermal emission engineering. In this review, we survey some of the main breakthroughs carried out in this burgeoning research field, from fundamental aspects to theoretical limits, the emergence of effects and phenomena, practical applications, challenges, and future prospects.

Monolithically integrated wide field-of-view metalens by angular dispersionless metasurface

Meta-lenses, which are made by sub-wavelength metallic or dielectric elements, have attracted widespread attentions due to its unprecedented electromagnetic wave manipulation abilities and novel applications. Dissimilar to previous metalens doublet by all-dielectric metasurfaces in the optical band, an innovative and more robust approach by angular dispersionless meta-atom to directly eliminate aberrations in low spectrum is proposed. As a proof of concept, an elaborately selected singlet metallic resonator for simultaneously high transmission, full phase coverage and the ignored angular dispersion is presented in the microwave. The designed metalens with only one single phase gradient profile can focus wide field-of-view (FOV) incident waves of ± 40° with both a large numerical aperture of 0.56 (NA = 0.56) and high focusing efficiency of 53 % on average at microwave regime. The metalens is also fabricated by a single-step printed circuit board technique and the measured high-performance focusing are also achieved for the entire FOV. The presented on-chip and integrated wide FOV metalens provides a simple yet cost-effective method to develop wide-angle metalenses especially in low frequency band where plasmonic metasurfaces are commonly adopted. Besides, its excellent wide-angle focusing performances can satisfy diverse applications in modern radar engineering such as imaging, sensing, communications and detection, etc.

Wideband Polarization‐Insensitive 1‐Bit Phase Manipulations with Co‐and Cross‐Polarized Conversions for LP and CP Waves

AbstractPolarization and phase manipulations have gained widespread applications across various fields. The emergence of metasurface provides a new platform for the manipulation of electromagnetic waves. However, most metasurfaces are limited to modulating only one single property. Here, a coding metasurface that achieves 1‐bit phase manipulations of both co‐polarized and cross‐polarized reflected waves for linear and circular polarization wave excitations. Notably, the proposed metasurface enables co‐polarized 1‐bit phase responses for incident electric fields with arbitrary orientations and spin directions. The simulated results demonstrate an operating efficiency over −1.7 dB in the frequency range from 7 to 11.1 GHz, with a relative bandwidth of 45.3%. Furthermore, the introduction of space‐polarization coding strategies facilitates the beam and polarization manipulations. To verify the feasibility of the coding metasurface, a sample and conduct experiments are fabricated, revealing good agreement between the simulations and measurements. These findings hold significant promise for the advancement of radar, imaging, and wireless communication systems, with potential applications in various domains.

Tailless Information-Energy Metasurface.

Programmable metasurface technology can achieve flexible manipulations of electromagnetic waves in real time by adjusting the surface structure and material properties and has shown extraordinary potential in many fields such as wireless communications and the Internet of Things. However, most of the programmable metasurfaces have a common feature: a tail (electrical wires and DC powers), which is difficult to supply in some particular application scenarios such as canyons and mountains. To eliminate the limitation of DC power supply, the programmable metasurface and wireless power transfer technology are combined to propose a tailless information-energy metasurface (IEMS). The tailless IEMS platform can dynamically control electromagnetic waves without relying on an external DC power supply; instead, the required DC power is provided internally by the IEMS platform itself. In the tailless IEMS experiments, the concept is demonstrated through the dynamic regulation of wireless channels and the wireless transmission of DC power. This work provides a self-powered method for programmable metasurfaces, expands the application scenarios, facilitates the miniaturization of systems, and makes it easy to integrate with other systems.

An angular stable ultra-broadband asymmetric transmission chiral metasurface with efficient linear-polarization conversion

Abstract In this paper, a chiral metasurface is presented to effectively attain an ultra-broadband operation of asymmetric transmission with highly efficient cross-polarization conversion. The efficiency of the asymmetric transmission operation in the frequency band ranging from 6.5 to 13 GHz is above 70%. Additionally, in the frequency range from 3.7 to 14 GHz, the cross-polarization conversion realizes greater than 90% polarization conversion ratio. Asymmetric transmission as well as cross-polarization conversion show angular stability against the incident angle of electromagnetic waves up to 45°. To validate the simulation results, the fabricated chiral metasurface is tested and compared with simulation results. The concepts of asymmetric transmission and linear-polarization conversion are demonstrated and physically explained through the distributions of surface currents over metallic layers. This anticipated work has significant applications in telecommunications and radar, as well as potential use in equipment designed for the manipulation of electromagnetic waves.

Reconfigurable Tri-Mode Metasurface for Broadband Low Observation, Wide-Range Tracing, and Backscatter Communication.

In the current prevalent complex electromagnetic (EM) environment, intelligent methods for versatile and integrated control of EM waves using compact devices are both essential and challenging. These varied wave control objectives can at times conflict with one another, such as the need for broad absorption to remain inconspicuous, while also requiring enhanced backward scattering for highly reliable tracing and secure communication. To address these sophisticated challenges, a microwave-frequency reconfigurable tri-mode metasurface (RTMM) is introduced. The proposed innovation enables three distinct operational modes: broadband low observation, enhanced EM wave tracing, and backscatter communication over a wide-angle range by simple control of the PIN diodes embedded in each meta-atom. The proof-of-concept demonstration of the fabricated prototype verified the switchable tri-mode performance of the RTMM. This proposed RTMM can be adapted to various applications, including EM shielding, target detection, and secure communication in complex and threatening EM environments, paving the way for environmentally-adaptive EM wave manipulation.

All-dielectric absorber based on nano-graphite sheets/ionogels with configurable absorbing band.

With the increasing complexity of the electromagnetic environment, there is a growing demand for the manipulation of electromagnetic waves, leading to the rapid development in configurable microwave absorbers. All-dielectric absorbers offer broadband and high-intensity absorption effects in microwave absorption and shielding. However, they face a significant challenge: their performance is not adjustable once the design is completed. In this study, we propose a solution to this problem by creating all-dielectric absorbers with flexibly configurable absorbing properties. We achieve this by designing a composite material of ionogels/nano-graphite sheets into compressible deformable absorbing units that can be molded into different shapes using 3D printing modes. The plasticity allows us to change the performance of the all-dielectric absorber, including the microwave absorption intensity, absorption peak, frequency bandwidths, and wide-angle absorption performance. With this approach, we can flexibly manipulate electromagnetic waves using all-dielectric absorbers through different plasticity models.

Multifunctional coding metasurface for focusing and beam deflection based on polarization selection

ABSTRACT In this paper, a full-space multifunctional coding metasurface (MS) with reflection and transmission integration is proposed to realize the independent manipulation of electromagnetic waves at two different frequencies. The unit consists of two layers of dielectric substrate and three layers of metal patch, the upper reflective layer is composed of a ring and a split ring (URSR), the middle layer is a split ring groove (MSR), and the lower transmission layer is a split ring (LSR). The transmission mode works at 13.4 GHz, incoming linear polarization (LP) waves to realize beam deflection with a deflection angle of 34°. While the reflection mode works at 17.9 GHz, beam focusing to achieved under the action of circular polarization (CP) waves. In order to verify the feasibility of the design, a circularly polarized antenna is placed at 80 mm in the metasurface -Z direction, and the gain increases from 7.5 dB to 22.5 dB. Meanwhile coding metasurface and circularly polarized microstrip antennas is fabricated and measured, and the results are consistent with the simulation results. The proposed method provides the possibility of high-rate transmission of information of multifunctional devices in communication systems.