- 标题
- 摘要
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- 实验方案
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Modular approach to understanding and synthesis of metamaterials and metasurfaces
摘要： The vast majority of previously proposed metamaterials and metasurfaces are anisotropic or bianisotropic (exhibiting magnetoelectric coupling). Nevertheless, their anisotropy was not fully exploited as they were designed only for one or several specific illumination directions. In this talk, we propose a simple analytical approach to characterize properties of general bianisotropic meta-atoms for an arbitrary illumination. The approach is based on the qualitative decomposition of an arbitrary meta-atom into separate basic “modules” with elementary polarization properties. Such decomposition can be used for comprehensive characterization of previously designed structures as well as for synthesizing novel bianisotropic inclusions of arbitrary complexity and with desired response.
关键词： polarization properties,anisotropy,metamaterials,bianisotropic,metasurfaces,magnetoelectric coupling
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Non-linearity Enhances Versatility of Non-Foster Metamaterials and Metasurfaces
摘要： Classical applications of non-Foster elements such as broadband active metamaterials/metasurfaces and broadband matching of small antennas presume their linearity. Here, we show that two well-known types of negative impedance converters - the voltage-conversion type and the current-conversion type, show fundamentally different behavior in non-liner regime. It is followed by different power-dependent properties of generated positive/negative susceptance/reactance. This effect may be used in future self-oscillating and self-mixing metasurfaces as well as in power-tunable metamaterials/metasurfaces.
关键词： negative impedance converters,non-linearity,metamaterials,non-Foster elements,metasurfaces
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Rapid characterization of metasurface unit cells using Scanning Differential Heterodyne Microscopy
摘要： The performance of metasurfaces is reduced due to factors like fabrication uncertainties and near-field coupling, which can be solved by direct characterization of individual elements. Recent techniques use near-field scanning to observe direct properties of elements, which use AFM tips that are not stable for large areas. In this study, we demonstrate Scanning Differential Heterodyne Microscopy (SDHM) technique as a tool for phase and amplitude characterization of unit cells in reflective phase-gradient metasurfaces with the aim to predict the far-field performance. The use of heterodyne 2-probe beam scanning to monitor surface modulations, provides fundamental advantage of rapid and robust phase-amplitude optical data acquisition essential for large scale metasurface investigations and applications.
关键词： phase and amplitude characterization,Scanning Differential Heterodyne Microscopy,SDHM,far-field performance,metasurfaces
更新于2025-09-10 09:29:36
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Machine-Learning Designs of Anisotropic Digital Coding Metasurfaces
摘要： Digital coding representations of meta-atoms make it possible to realize intelligent designs of metasurfaces by means of machine learning algorithms. Here, a machine-learning method to design anisotropic digital coding metasurfaces is proposed, and meta-atoms may require any absolute phase values at di?erent positions and under di?erent polarizations. A deep-learning neural network to predict the vast and complex system is proposed, in which only 70 000 training coding patterns are used to train the network. Another 10 000 randomly chosen coding patterns are employed to validate the neural network, showing an accuracy of 90.05% of phase responses with 2° error in the 360° phase. Using the learned network, the correct coding pattern among 18 billion of billions of choices for the required phase can be readily found in a second, ?nishing automatic design of anisotropic meta-atoms. Three functional 1-bit anisotropic coding metasurfaces are intelligently achieved by the learned network. It is convenient to realize dual-beam scattering with left-handed circular polarization (LHCP) for one beam while right-handed circular polarization (RHCP) for the others, dual-beam scattering with circular polarization for one beam while linear polarization (LP) for the others, and triple-beam scattering with LHCP and RHCP for two beams while LP for the third one.
关键词： anisotropic elements,multiple controls,digital coding metasurfaces,machine-learning
更新于2025-09-10 09:29:36
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Independent control of harmonic amplitudes and phases via a time-domain digital coding metasurface
摘要： Harmonic manipulations are important for applications such as wireless communications, radar detection and biological monitoring. A general approach to tailor the harmonics involves the use of additional amplifiers and phase shifters for the precise control of harmonic amplitudes and phases after the mixing process; however, this approach leads to issues of high cost and system integration. Metasurfaces composed of a periodic array of subwavelength resonators provide additional degrees of freedom to realize customized responses to incident light and highlight the possibility for nonlinear control by taking advantage of time-domain properties. Here, we designed and experimentally characterized a reflective time-domain digital coding metasurface, with independent control of the harmonic amplitude and phase. As the reflection coefficient is dynamically modulated in a predefined way, a large conversion rate is observed from the carrier signal to the harmonic components, with magnitudes and phases that can be accurately and separately engineered. In addition, by encoding the reflection phases of the meta-atoms, beam scanning for multiple harmonics can be implemented via different digital coding sequences, thus removing the need for intricate phase-shift networks. This work paves the way for efficient harmonic control for applications in communications, radar, and related areas.
关键词： time-domain digital coding metasurface,metasurfaces,radar detection,nonlinear control,harmonic manipulations,wireless communications,beam scanning,biological monitoring
更新于2025-09-10 09:29:36
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Acoustic perfect absorbers via spiral metasurfaces with embedded apertures
摘要： In this work, we analytically and experimentally present perfect acoustic absorbers via spiral metasurfaces composed of coiled channels and embedded apertures. Perfect absorption (reaching 0.999 in experiments) is realized with an ultra-thin thickness down to (cid:2)1/100th of the operating wavelength. Owing to the superior impedance manipulation provided by the embedded apertures, perfect absorption with tunable frequencies is demonstrated. Our results would contribute to paving a way towards designing thin and light absorbers for the low frequency absorption challenge.
关键词： embedded apertures,spiral metasurfaces,impedance manipulation,acoustic perfect absorbers,low frequency absorption
更新于2025-09-09 09:28:46
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Nonlinear Quasi-Phase Matching with metasurfaces
摘要： Quasi-Phase Matching is an optical process needed to build up nonlinear signal from strong pump intensity and is generally obtained through periodical inversion of coherence domains of the crystal. We show that this effect can be arti?cially monitored through inserting metasurfaces along the optical path of the light in a waveguide. Sub-wavelength gratings of holes are etched in Gallium Nitride to locally change medium dispersion, allowing continuous increase of the second harmonic signal. This approach can be used to address any phase delay difference between pump and signal at will, not only π, opening up new perspectives for arbitrary phase matching conditions. It can also be implemented in highly nonlinear systems, in which it is generally hard to address phase-matching conditions, for instance waveguides with buried intersubband quantum wells or other materials such GaAs.
关键词： second harmonic generation,metasurfaces,Quasi-Phase Matching,Gallium Nitride,nonlinear optics
更新于2025-09-09 09:28:46
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Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering
摘要： Modulation of metasurfaces in time gives rise to several exotic space-time scattering phenomena by breaking the reciprocity constraint and generation of higher-order frequency harmonics. We introduce a new design paradigm for time-modulated metasurfaces, enabling tunable engineering of the generated frequency harmonics and their emerging wavefronts by electrically controlling the phase delay in modulation. It is demonstrated that the light acquires a dispersionless phase shift regardless of incident angle and polarization, upon undergoing frequency conversion in a time-modulated metasurface which is determined by the modulation phase delay and the order of generated frequency harmonic. The conversion efficiency to the frequency harmonics is independent of modulation phase delay and only depends on the modulation depth and resonant characteristics of the metasurface element, with the highest efficiency occurring in the vicinity of resonance, and decreasing away from the resonance. The modulation-induced phase shift allows for creating tunable spatially varying phase discontinuities with 2π span at the generated frequency harmonics for a wide range of frequencies and incident angles. Specifically, we apply this approach to a time-modulated metasurface in the Terahertz regime consisted of graphene-wrapped silicon microwires. For this purpose, we use an accurate and efficient semi-analytical framework based on multipole scattering. We demonstrate the utility of the design rule for tunable beam steering and focusing of generated frequency harmonics, giving rise to several intriguing effects such as spatial decomposition of harmonics, anomalous bending with full coverage of angles and dual-polarity lensing. Furthermore, we investigate the angular and spectral performance of the time-modulated metasurface in manipulation of generated frequency harmonics to verify its constant phase response versus incident wavelength and angle. The nonreciprocal response of the metasurface in wavefront engineering is also studied by establishing nonreciprocal links via modulation-induced phase shift. The proposed design approach enables a new class of high-efficiency tunable metasurfaces with wide angular and frequency bandwidth, wavefront engineering capabilities, nonreciprocal response and multi-functionality.
关键词： Terahertz,wavefront engineering,nonreciprocal response,graphene,time-modulation,metasurfaces
更新于2025-09-09 09:28:46
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Deep-subwavelength control of acoustic waves in an ultra-compact metasurface lens
摘要： Space-coiling acoustic metasurfaces have been largely exploited and shown their outstanding wave manipulation capacity. However, they are complex in realization and cannot directly manipulate acoustic near-fields by controlling the effective path length. Here, we propose a comprehensive paradigm for acoustic metasurfaces to extend the wave manipulations to both far- and near-fields and markedly reduce the implementation complexity with a simple structure, which consists of an array of deep-subwavelength-spaced slits perforated in a thin plate. A semi-analytical approach for such a design is established using a microscopic coupled-wave model, which reveals that the acoustic diffractive pattern at every slit exit is the sum of the initial transmission and the secondary scatterings of the coupled fields from other slits. For proof-of-concept, we examine two metasurface lenses for sound focusing within and beyond the diffraction limit. This work provides a feasible strategy for creating ultra-compact acoustic components with versatile potentials.
关键词： acoustic metasurfaces,sound focusing,microscopic coupled-wave model,wave manipulation,deep-subwavelength
更新于2025-09-09 09:28:46
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Metamaterials and metasurfaces for designing metadevices: Perfect absorbers and microstrip patch antennas
摘要： In the past twenty years, electromagnetic metamaterials represented by left-handed metamaterials (LHMs) have attracted considerable attention due to the unique properties such as negative refraction, perfect lens, and electromagnetic cloaks. In this paper, we present a comprehensive review of our group’s work on metamaterials and metasurfaces. We present several types of LHMs and chiral metamaterials. As a two-dimensional equivalent of bulk three-dimensional metamaterials, metasurfaces have led to a myriad of devices due to the advantages of lower profile, lower losses, and simpler to fabricate than bulk three-dimensional metamaterials. We demonstrate the novel microwave metadevices based on metamaterials and metasurfaces: perfect absorbers and microwave patch antennas, including novel transmission line antennas, high gain resonant cavity antennas, wide scanning phased array antennas, and circularly polarized antennas.
关键词： microstrip patch antennas,metasurfaces,chiral metamaterials,perfect absorbers,left-handed metamaterials
更新于2025-09-09 09:28:46