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Sarwat A Baig, Jessica L Boland, Djamshid A Damry, Hark Hoe Tan, Chennupati Jagadish, Hannah J Joyce, Michael B Johnston
Progress in the terahertz (THz) region of the electromagnetic spectrum is undergoing major advances, with advanced THz sources and detectors being developed at a rapid pace. Yet, ultrafast THz communication is still to be realised, owing to the lack of practical and effective THz modulators. Here, we present a novel ultrafast active THz polarization modulator based on GaAs semiconductor nanowires arranged in a wire-grid configuration. We utilise an optical pump--terahertz probe spectroscopy system and vary the polarization of the optical pump beam to demonstrate ultrafast THz modulation with a switching time of less than 5\,ps and a modulation depth of -8dB...
March 23, 2017: Nano Letters
Dong Wu, Yumin Liu, Li Yu, Zhongyuan Yu, Lei Chen, Ruifang Li, Rui Ma, Chang Liu, Jinqiannan Zhang, Han Ye
In this work, using finite-difference time-domain method, we propose and numerically demonstrate a novel way to achieve electromagnetically induced transparency (EIT) phenomenon in the reflection spectrum by stacking two different types of coupling effect among different elements of the designed metamaterial. Compared with the conventional EIT-like analogues coming from only one type of coupling effect between bright and dark meta-atoms on the same plane, to our knowledge the novel approach is the first to realize the optically active and precise control of the wavelength position of EIT-like phenomenon using optical metamaterials...
March 23, 2017: Scientific Reports
Zhaoyun Duan, Xianfeng Tang, Zhanliang Wang, Yabin Zhang, Xiaodong Chen, Min Chen, Yubin Gong
Reversed Cherenkov radiation is the exotic electromagnetic radiation that is emitted in the opposite direction of moving charged particles in a left-handed material. Reversed Cherenkov radiation has not previously been observed, mainly due to the absence of both suitable all-metal left-handed materials for beam transport and suitable couplers for extracting the reversed Cherenkov radiation signal. In this paper, we develop an all-metal metamaterial, consisting of a square waveguide loaded with complementary electric split ring resonators...
March 23, 2017: Nature Communications
Bui Xuan Khuyen, Bui Son Tung, Young Joon Yoo, Young Ju Kim, Ki Won Kim, Liang-Yao Chen, Vu Dinh Lam, YoungPak Lee
An efficient resolution for ultrathin metamaterial perfect absorber (MPA) is proposed and demonstrated in the VHF radio band (30-300 MHz). By adjusting the lumped capacitors and the through vertical interconnects, the absorber is miniaturized to be only λ/816 and λ/84 for its thickness and periodicity with respect to the operating wavelength (at 102 MHz), respectively. The detailed simulation and calculation show that the MPA can maintain an absorption rate over 90% in a certain range of incident angle and with a wide variation of capacitance...
March 22, 2017: Scientific Reports
Michael J Frazier, Dennis M Kochmann
A mechanical metamaterial, a simple, periodic mechanical structure, is reported, which reproduces the nonlinear dynamic behavior of materials undergoing phase transitions and domain switching at the structural level. Tunable multistability is exploited to produce switching and transition phenomena whose kinetics are governed by the same Allen-Cahn law commonly used to describe material-level, structural-transition processes. The reported purely elastic mechanical system displays several key features commonly found in atomic- or mesoscale physics of solids...
March 21, 2017: Advanced Materials
Bo Gao, Matthew M F Yuen, Terry Tao Ye
Metamaterials have attracted more and more research attentions recently. Metamaterials for electromagnetic applications consist of sub-wavelength structures designed to exhibit particular responses to an incident EM (electromagnetic) wave. Traditional EM (electromagnetic) metamaterial is constructed from thick and rigid structures, with the form-factor suitable for applications only in higher frequencies (above GHz) in microwave band. In this paper, we developed a thin and flexible metamaterial structure with small-scale unit cell that gives EM metamaterials far greater flexibility in numerous applications...
March 21, 2017: Scientific Reports
Nan Yang, Jesse L Silverberg
A defining feature of mechanical metamaterials is that their properties are determined by the organization of internal structure instead of the raw fabrication materials. This shift of attention to engineering internal degrees of freedom has coaxed relatively simple materials into exhibiting a wide range of remarkable mechanical properties. For practical applications to be realized, however, this nascent understanding of metamaterial design must be translated into a capacity for engineering large-scale structures with prescribed mechanical functionality...
March 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
Cheng Zhang, Nathaniel Kinsey, Long Chen, Chengang Ji, Mingjie Xu, Marcello Ferrera, Xiaoqing Pan, Vladimir M Shalaev, Alexandra Boltasseva, L Jay Guo
The field of nanophotonics has ushered in a new paradigm of light manipulation by enabling deep subdiffraction confinement assisted by metallic nanostructures. However, a key limitation which has stunted a full development of high-performance nanophotonic devices is the typical large losses associated with the constituent metals. Although silver has long been known as the highest quality plasmonic material for visible and near infrared applications, its usage has been limited due to practical issues of continuous thin film formation, stability, adhesion, and surface roughness...
March 20, 2017: Advanced Materials
Marc Dubois, Chengzhi Shi, Xuefeng Zhu, Yuan Wang, Xiang Zhang
Zero index materials where sound propagates without phase variation, holds a great potential for wavefront and dispersion engineering. Recently explored electromagnetic double zero index metamaterials consist of periodic scatterers whose refractive index is significantly larger than that of the surrounding medium. This requirement is fundamentally challenging for airborne acoustics because the sound speed (inversely proportional to the refractive index) in air is among the slowest. Here, we report the first experimental realization of an impedance matched acoustic double zero refractive index metamaterial induced by a Dirac-like cone at the Brillouin zone centre...
March 20, 2017: Nature Communications
Allan D Boardman, Alessandro Alberucci, Gaetano Assanto, Vladimir Grimalsky, Bertrand Kibler, Jim McNiff, Igor Nefedov, Yuriy Rapoport, Costas Valagiannopoulos
The topics here deal with some current progress in electromagnetic wave propagation in a family of substances known as metamaterials. To begin with, it is discussed how a pulse can develop a leading edge that steepens and it is emphasised that such self-steepening is an important inclusion within a metamaterial environment together with Raman scattering and third-order dispersion whenever very short pulses are being investigated. It is emphasised that the self-steepening parameter is highly metamaterial-driven compared to Raman scattering, which is associated with a coefficient of the same form whether a normal positive phase, or a metamaterial waveguide is the vehicle for any soliton propagation...
March 17, 2017: Nanotechnology
Carles Navau, Rosa Mach-Batlle, Albert Parra, Jordi Prat-Camps, Sergi Laut, Nuria Del-Valle, Alvaro Sanchez
Magnetic sensors are key elements in our interconnected smart society. Their sensitivity becomes essential for many applications in fields such as biomedicine, computer memories, geophysics, or space exploration. Here we present a universal way of increasing the sensitivity of magnetic sensors by surrounding them with a spherical metamaterial shell with specially designed anisotropic magnetic properties. We analytically demonstrate that the magnetic field in the sensing area is enhanced by our metamaterial shell by a known factor that depends on the shell radii ratio...
March 17, 2017: Scientific Reports
Yoav Kallus, Miranda Holmes-Cerfon
Networks of particles connected by springs model many condensed-matter systems, from colloids interacting with a short-range potential and complex fluids near jamming, to self-assembled lattices and various metamaterials. Under small thermal fluctuations the vibrational entropy of a ground state is given by the harmonic approximation if it has no zero-frequency vibrational modes, yet such singular modes are at the epicenter of many interesting behaviors in the systems above. We consider a system of N spherical particles, and directly account for the singularities that arise in the sticky limit where the pairwise interaction is strong and short ranged...
February 2017: Physical Review. E
Ming Lun Tseng, Xu Fang, Vassili Savinov, Pin Chieh Wu, Jun-Yu Ou, Nikolay I Zheludev, Din Ping Tsai
Far-field spectroscopy and mapping of electromagnetic near-field distribution are the two dominant tools for analysis and characterization of the electromagnetic response in nanophotonics. Despite the widespread use, these methods can fail at identifying weak electromagnetic excitations masked by stronger neighboring excitations. This is particularly problematic in ultrafast nanophotonics, including optical sensing, nonlinear optics and nanolasers, where the broad resonant modes can overlap to a significant degree...
March 15, 2017: Scientific Reports
M Okuda, T Schwarze, J-C Eloi, S E Ward Jones, P J Heard, A Sarua, E Ahmad, V V Kruglyak, D Grundler, W Schwarzacher
We show that chemical fixation enables top-down micro-machining of large periodic 3D arrays of protein-encapsulated magnetic nanoparticles (NPs) without loss of order. We machined 3D micro-cubes containing a superlattice of NPs by means of focused ion beam etching, integrated an individual micro-cube to a thin-film coplanar waveguide and measured the resonant microwave response. Our work represents a major step towards well-defined magnonic metamaterials created from the self-assembly of magnetic nanoparticles...
April 18, 2017: Nanotechnology
Angela Madeo, Patrizio Neff, Elias C Aifantis, Gabriele Barbagallo, Marco Valerio d'Agostino
In this paper, the role of gradient micro-inertia terms [Formula: see text] and free micro-inertia terms [Formula: see text] is investigated to unveil their respective effects on the dynamic behaviour of band-gap metamaterials. We show that the term [Formula: see text] alone is only able to disclose relatively simplified dispersive behaviour. On the other hand, the term [Formula: see text] alone describes the full complex behaviour of band-gap metamaterials. A suitable mixing of the two micro-inertia terms allows us to describe a new feature of the relaxed-micromorphic model, i...
February 2017: Proceedings. Mathematical, Physical, and Engineering Sciences
Zhiwang Zhang, Qi Wei, Ying Cheng, Ting Zhang, Dajian Wu, Xiaojun Liu
The discovery of topological acoustics has revolutionized fundamental concepts of sound propagation, giving rise to strikingly unconventional acoustic edge modes immune to scattering. Because of the spinless nature of sound, the "spinlike" degree of freedom crucial to topological states in acoustic systems is commonly realized with circulating background flow or preset coupled resonator ring waveguides, which drastically increases the engineering complexity. Here we realize the acoustic pseudospin multipolar states in a simple flow-free symmetry-broken metamaterial lattice, where the clockwise (anticlockwise) sound propagation within each metamolecule emulates pseudospin down (pseudospin up)...
February 24, 2017: Physical Review Letters
D Jalas, L-H Shao, R Canchi, T Okuma, S Lang, A Petrov, J Weissmüller, M Eich
Using optical in-situ measurements in an electrochemical environment, we study the electrochemical tuning of the transmission spectrum of films from the nanoporous gold (NPG) based optical metamaterial, including the effect of the ligament size. The long wavelength part of the transmission spectrum around 800 nm can be reversibly tuned via the applied electrode potential. The NPG behaves as diluted metal with its transition from dielectric to metallic response shifted to longer wavelengths. We find that the applied potential alters the charge carrier density to a comparable extent as in experiments on gold nanoparticles...
March 9, 2017: Scientific Reports
Hai-Long Zhang, Yi-Fan Zhu, Bin Liang, Jing Yang, Jun Yang, Jian-Chun Cheng
Suppression of the transmission of undesired sound in ducts is a fundamental issue with wide applications in a great variety of scenarios. Yet the conventional ways of duct noise control have to rely on mismatched impedance or viscous dissipation, leading the ducts to have ventilation capability weakened by inserted absorbers or a thick shell to accommodate bulky resonators. Here we present a mechanism for insulating sound transmission in a hollow pipe with subwavelength thickness, by directly reversing its propagating direction via anomalous reflection at the flat inner boundary with well-designed phase profile...
March 8, 2017: Scientific Reports
Sotiris Droulias, Aditya Jain, Thomas Koschny, Costas M Soukoulis
The route to miniaturization of laser systems has so far led to the utilization of diverse materials and techniques for reaching the desired laser oscillation at small scales. Unfortunately, at some point all approaches encounter a trade-off between the system dimensions and the Q factor, especially when going subwavelength, mostly because the radiation damping is inherent to the oscillating mode and can thus not be controlled separately. Here, we propose a metamaterial laser system that overcomes this trade-off and offers radiation damping tunability, along with many other features, such as directionality, subwavelength integration, and simple layer-by-layer fabrication...
February 17, 2017: Physical Review Letters
Victor Ya Prinz, Elena V Naumova, Sergey V Golod, Vladimir A Seleznev, Andrey A Bocharov, Vitaliy V Kubarev
Electromagnetic metamaterials opened the way to extraordinary manipulation of radiation. Terahertz (THz) and optical metamaterials are usually fabricated by traditional planar-patterning approaches, while the majority of practical applications require metamaterials with 3D resonators. Making arrays of precise 3D micro- and nanoresonators is still a challenging problem. Here we present a versatile set of approaches to fabrication of metamaterials with 3D resonators rolled-up from strained films, demonstrate novel THz metamaterials/systems, and show giant polarization rotation by several chiral metamaterials/systems...
March 3, 2017: Scientific Reports
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