Advances in additive manufacturing will enable the fabrication of metamaterials with ever more complex architectures, to realize unusual and superior physical properties. The authors design and build lattices of sinusoidal beams, yielding a class of metamaterials with unusual, extreme mechanical behavior: Poisson’s ratio for the system switches from negative to positive upon large deformation (the nonlinear regime). Potential applications include energy absorption, tunable acoustics, vibration control, responsive devices, soft robotics, and stretchable electronics.
[Phys. Rev. Applied 7, 024012] Published Thu Feb 09, 2017
]]>is an active subject in information processing, because of its utility in constructing electromagnetic and acoustic devices. The authors present a multiband, subwavelength acoustic device based on a “coded metasurface”, an alternating arrangement of elements corresponding to bit values of 0 or 1. By assembling these building blocks to encode patterns such as 0000…, 1111…, or 0101…, asymmetric transmission can be handily controlled to select “off” and “on” states.
[Phys. Rev. Applied 7, 024010] Published Thu Feb 09, 2017
]]>We have experimentally and numerically studied the directional birefringence of -band microwaves by magnetochiral (MCh) effects of a single metamolecule under dc magnetic fields at room temperature. Phase and amplitude transmission coefficients from top and bottom, i.e., parameters of and …
[Phys. Rev. B 95, 085402] Published Thu Feb 02, 2017
]]>Light waves propagating in optical fibers or other guides are usually vulnerable to defects or channel deformations, such as twisting and bending. These perturbations invariably generate undesired reflections and scattering and typically imply a power penalty. Here, building on an analogy with electronics and with the spin Hall effect, the author unveils a general theoretical solution for this dilemma. It is shown that there is a wide class of three-dimensional metamaterial platforms protected by a particular symmetry – a combination of a geometrical operation with other more subtle symmetries of the materials response – that guarantees bidirectional transport of light totally free of reflections, independent of the specific geometry of the propagation channel and other imperfections. Crucially, this scattering anomaly only requires the symmetry protection in the frequency range of interest, and hence relies on much weaker assumptions than topological theories.
[Phys. Rev. B 95, 035153] Published Mon Jan 30, 2017
]]>We have designed and fabricated a metamaterial consisting of planar metamolecules which exhibit unusual, almost perfect anapole behavior in the sense that the electric dipole radiation is almost canceled by the toroidal dipole one, producing thus an extremely high -factor at the resonance frequency…
[Phys. Rev. B 95, 035104] Published Tue Jan 03, 2017
]]>Sound absorption is a significant issue in acoustics and relevant to many applications, but current approaches suffer from either bulky dimensions or narrow bandwidth. The authors create an acoustic metamaterial consisting of curled, hollow, dead-end channels, which can totally absorb sound in a band of low frequencies. The position and width of the band can be tuned by adjusting the lengths and number of channels in a unit cell, respectively.
[Phys. Rev. Applied 6, 064025] Published Thu Dec 29, 2016
]]>Cloaking techniques usually rely on external tools, such as metamaterial or plasmonic covers, or active sources. On the other hand, cloaking based on mechanisms might offer unique advantages for applications. The authors show that a homogeneous ferrite rod can be “self-invisible” when its induced magnetic dipole has a quarter-cycle response delay relative to an external magnetic field, minimizing its scattering efficiency. Field-tunable visibility of such rods in a photonic crystal allows different functionalities in one device, with the fast switching time that a magnetic system offers.
[Phys. Rev. Applied 6, 061001] Published Fri Dec 16, 2016
]]>The ability to design material architecture at the microscale has led to systems with extreme quasistatic properties, such as zero shear modulus and negative Poisson’s ratio. To extend their range of applications, to ultrasonics, what about their dynamical properties? The authors present microlattices that are acoustically transparent to waves in water over broad frequency ranges, yet still effectively attenuate waves in other ranges. This work has important implications for ultrasonic transducers in biomedical imaging and single-cell surgery.
[Phys. Rev. Applied 6, 064005] Published Fri Dec 09, 2016
]]>Materials with nontrivial topological order may be engineered to have electrically conducting surface states despite an insulating bulk. Analogies have also been found for photons and phonons, with most systems designed to demonstrate a particular feature. Going a step beyond, the authors show how to implement a regular lattice of simple, achiral objects (here cylinders) as a topological insulator that can be reconfigured . This approach allows dynamic control of chirality and other lattice properties, including surface states, and paves the wave for applications in topological computing and signal processing.
[Phys. Rev. Applied 6, 064006] Published Fri Dec 09, 2016
]]>Qubits are necessary for next-generation quantum computers. Researchers theoretically demonstrate a topological fluid of photons to simulate such qubits.
[Phys. Rev. X 6, 041043] Published Thu Dec 01, 2016
]]>Acoustic metamaterials have the potential to reduce environmental noise, but conventional structures are impractically large for low frequencies. Thus subwavelength systems for sound control have attracted growing attention. The authors present a simple, efficient way to absorb sound inside a waveguide by means of Helmholtz resonators, which are very small compared to the wavelength. This suggests applications such as attenuating undesirable room modes, or noise in ventilation ducts.
[Phys. Rev. Applied 6, 054021] Published Tue Nov 29, 2016
]]>When coupled to a tuning mechanism, a disordered medium provides a powerful means for shaping electromagnetic waveforms. The authors leverage this functionality to conduct volumetric computational imaging: A deformed cavity is outfitted with tailored, irregular surfaces, and its microwave resonant modes are projected into an imaging domain to retrieve the scene’s spatial information. This approach could be applied to biomedical imaging, security screening, or wireless power transfer or telecommunications.
[Phys. Rev. Applied 6, 054019] Published Tue Nov 29, 2016
]]>An object can be commonly thought of as rigid or floppy. Now, scientists design and build periodic gear assemblies that can have topological floppy modes.
[Phys. Rev. X 6, 041029] Published Tue Nov 08, 2016
]]>Metasurfaces (metamaterials of near-vanishing thickness) are of interest for engineering subwavelength structures with complex responses. Typically a graphene metasurface exhibits just one or two resonances and absorbs light in a narrow frequency band, but this study demonstrates tunable broadband absorption due to hierarchical, fractal structuring. Over a very wide band (about 190% of the central frequency), the average absorption exceeds 20%, without any metallic mirror. This approach to broadband absorbers, and plasmonic components more generally, offers substantially improved performance at terahertz and optical frequencies.
[Phys. Rev. Applied 6, 044019] Published Fri Oct 28, 2016
]]>When its corners are switched from disconnected to connected, a metallic checkerboard exhibits a sort of insulator-metal transition in its electromagnetic response. To use this phenomenon for dynamic polarization control, which is essential for polarization-selective spectroscopy, the authors study anisotropy as a general means to artificially engineer phase transitions of checkerboardlike metasurfaces. Application of this approach to yield a dynamic terahertz polarizer is discussed.
[Phys. Rev. Applied 6, 044022] Published Fri Oct 28, 2016
]]>Lenses are critical to a variety of fields of science, but optical aberrations such as astigmatism are common problems. A “perfect” lens made of two metasurfaces is theoretically developed.
[Phys. Rev. X 6, 041018] Published Tue Oct 25, 2016
]]>Metasurfaces are engineered systems that enable advanced control of electromagnetic waves over deeply subwavelength thicknesses. Researchers make a careful study of the use of metasurfaces to transform the impinging optical wave front.
[Phys. Rev. X 6, 041008] Published Fri Oct 14, 2016
]]>Recently, it was shown that by using special artificial materials it is possible to ensure that all electromagnetic modes of free space are conjugately matched to the modes of a material body and, thus, all modes deliver power to the body in the most effective way. Such a fascinating feature is acqu…
[Phys. Rev. B 94, 125117] Published Mon Sep 12, 2016
]]>We often consider bulk metamaterials with engineered electromagnetic properties, or even metasurfaces, but what about an individual ? The authors study the magnetization configuration of an isolated, micrometer-sized metamolecule, designed and cleverly fabricated to break both space-inversion and time-reversal symmetry. Such a system could be used for a one-way mirror controlled by magnetic field, or as an artificial multiferroic material operating at convenient fields and temperatures.
[Phys. Rev. Applied 6, 024016] Published Wed Aug 24, 2016
]]>Nonuniform metasurfaces (electrically thin composite layers) can be used for shaping refracted and reflected electromagnetic waves. However, known design approaches based on the generalized refraction and reflection laws do not allow realization of perfectly performing devices: there are always some…
[Phys. Rev. B 94, 075142] Published Fri Aug 19, 2016
]]>Conventional wisdom suggests that when a beam of light illuminates a particle, the radiation pressure pushes it in the direction of the light flow, downstream. However, under the right conditions, the particles can be made to move , toward the light source. Here the authors describe a means to transport engineered chiral nanoparticles with an “optical conveyor belt” that can move in . Simply controlling the helicity of the incoming wave enables switching between persistent attractive or repulsive optical forces, with just one beam and no optical traps.
[Phys. Rev. Applied 6, 014016] Published Wed Jul 27, 2016
]]>A so-called anti-optic-null medium (anti-ONM), which can be utilized to cancel the optic-null medium (ONM) and create many novel optical illusions, is introduced and designed by transformation optics (TO). Optical separation illusions can be achieved with an anti-ONM. With the help of the anti-ONM, …
[Phys. Rev. B 94, 045117] Published Fri Jul 15, 2016
]]>One of graphene’s interesting properties is that, when pumped by a laser at near-infrared and visible frequencies, it offers amplification at terahertz (THz) frequencies, which are useful for remote sensing in security applications. The authors explain how to take advantage of exotic parity-time () symmetry in an active graphene metasurface that realizes reciprocal, unidirectional reflectionless propagation of THz waves. This suggests exciting prospects for detecting chemical and biological agents with ultrahigh sensitivity.
[Phys. Rev. Applied 5, 064018] Published Wed Jun 29, 2016
]]>Light-matter interactions often depend on the light’s state of polarization (SOP), but actually measuring this SOP can be difficult, as the phase information between orthogonal polarization states is completely lost in conventional, intensity-based, detection. Using multiple birefringent plasmonic metasurfaces, the authors propose a compact polarimeter that is well suited for in-plane optical circuitry and allows facile determination of the SOP, as illustrated for the telecommunication wavelength of 1550 nm.
[Phys. Rev. Applied 5, 064015] Published Mon Jun 27, 2016
]]>allows one to design electromagnetic media to modify the trajectory of light in complex ways, as in an invisibility cloak. In this approach, an electromagnetic field undergoes a rotation and scaling, which restricts the achievable functionalities. What if there were another way? The authors present an alternative transformation theory that a field’s orientation and amplitude, allowing different effects and applications, including devices that feel no local electromagnetic force, which would help to shield systems from damage at high energies.
[Phys. Rev. Applied 5, 064008] Published Fri Jun 17, 2016
]]>Though metasurfaces continue to draw much attention, a comprehensive description of the properties of metasurfaces is still needed. This is a daunting problem for micromagnetic modeling, due to its multiple length scales from nm to cm, so an analytical approach is sought. The authors develop a scattering-matrix formalism using boundary conditions independent of the coordinate system, and then study the example of efficient reflection from a metasurface inside a microwave waveguide. Their approach should enable much further work.
[Phys. Rev. Applied 5, 064005] Published Thu Jun 09, 2016
]]>A lossy anisotropic epsilon-near-zero (ENZ) medium may lead to a counterintuitive phenomenon of omnidirectional bending-to-normal refraction [S. Feng, Phys. Rev. Lett. 108, 193904 (2012)], which offers a fabulous strategy for energy collimation and energy harvesting. Here, in the scope of effective …
[Phys. Rev. B 93, 245118] Published Wed Jun 08, 2016
]]>Topological insulators are of practical interest for the one-way wave propagation afforded by their edge states, and are not limited to electronic systems. In many cases the topological transition occurs when time-reversal symmetry is broken and is not tunable, but here the authors design a phononic crystal with a transition that be tuned by varying the structure’s geometric size, or the external airflow (velocity field). Their results are universal and should expand our ability to tailor sound waves, as in acoustic diodes.
[Phys. Rev. Applied 5, 054021] Published Fri May 27, 2016
]]>Acoustic waves are key to applications involving underwater communication and sonar, for example. Directional sensing of low-frequency (long-wavelength) sound is hampered, however, by the diffraction limit, which would necessitate inconveniently large (and probably immobile) detectors. The authors use the bounded metasurface surrounding a particle’s rigid core to modulate acoustic pressures by an order of magnitude. Angle-dependent dipolar resonances allow direction-sensitive detection of plane waves, despite that the structures are far smaller than the wavelength.
[Phys. Rev. Applied 5, 054015] Published Mon May 23, 2016
]]>Conventional solar cells cannot collect energy from abundant midinfrared light, because there are no suitable semiconductors of the right band gap. Hyperbolic metamaterials (HMMs) are proposed to realize broadband, omnidirectional, sensitive diodes operating in this spectral region. The authors show how the slow-light modes supported by HMMs can trap incident radiation in metal-insulator-metal tunnel junctions, for ultrafast optical rectification and photon-to-electron energy conversion that is orders of magnitude more efficient than in conventional optical rectennas.
[Phys. Rev. Applied 5, 041001] Published Thu Apr 28, 2016
]]>We investigate the nonlinear wave dynamics of origami-based metamaterials composed of Tachi-Miura polyhedron (TMP) unit cells. These cells exhibit strain softening behavior under compression, which can be tuned by modifying their geometrical configurations or initial folded conditions. We assemble t…
[Phys. Rev. E 93, 043004] Published Fri Apr 15, 2016
]]>The canonical Su-Schrieffer-Heeger (SSH) array is one of the basic geometries that have spurred significant interest in topological band-gap modes. Here, we show that the judicious inclusion of third-order Kerr nonlinearities in SSH arrays opens rich physics in topological insulators, including the …
[Phys. Rev. B 93, 155112] Published Thu Apr 07, 2016
]]>To realize useful, exotic properties, acoustic metamaterials for airborne sound traditionally have relied on materials that are much harder than the surrounding fluid. Soft acoustic metamaterials utilizing mesoporous silica aerogel structures offer an alternative means to tune the effective properties of the resulting metamaterial, while simultaneously providing better coupling to the acoustic environment. This study presents systems demonstrating negative density, density near zero, and nonresonant, broadband “slow sound” propagation.
[Phys. Rev. Applied 5, 034012] Published Wed Mar 30, 2016
]]>Origami offers the possibility for new metamaterials whose overall mechanical properties can be programed by acting locally on each crease. Starting from a thin plate and having knowledge about the properties of the material and the folding procedure, one would like to determine the shape taken by t…
[Phys. Rev. E 93, 033005] Published Tue Mar 22, 2016
]]>Photonic crystals may be engineered to steer light as desired, but surface effects must be carefully managed in real devices, adding complexity to their design and manufacture. The authors find topologically induced interface states that do not require any surface decoration, and can be predicted solely from the properties of the bulk photonic crystal. Without the need for surface decorations, designing and fabricating such systems will be much simpler than for today’s structures, showing a way forward to next-generation optical wave-guiding applications.
[Phys. Rev. Applied 5, 034009] Published Thu Mar 17, 2016
]]>Bulk hexagonal boron nitride (hBN) has recently attracted attention due to its unique directionally dependent optical properties. Usually a metamaterial must be meticulously designed and fabricated, but it happens that hBN is a . The authors report room-temperature emission of single photons from bulk hBN, and the associated photodynamics. These results point to using hBN as a platform for a broad range of applications in nanophotonics and quantum optics.
[Phys. Rev. Applied 5, 034005] Published Thu Mar 10, 2016
]]>One-way propagation of acoustic waves has been achieved using acoustic superlattices or nonlinear acoustic diodes, but these structures are much larger than the acoustic wavelength. This makes them impractical for applications such as low-frequency underwater signal transmission. The authors show that unidirectional acoustic wave propagation is possible with a device much smaller than the wavelength. Their design offers high rectification and broadband performance, and does not require an external power source.
[Phys. Rev. Applied 5, 034006] Published Thu Mar 10, 2016
]]>Electronic topological insulators are one of the breakthroughs of 21st century condensed matter physics. So far, the search for a light counterpart of an electronic time-reversal invariant topological insulator has remained elusive. This is due to the fundamentally different natures of light and mat…
[Phys. Rev. B 93, 075110] Published Thu Feb 04, 2016
]]>Thin films are central to modern technologies ranging from semiconductors to metamaterials. The authors observe that by placing a subwavelength thin film at the node of an electromagnetic standing wave, it is possible to separate electric from magnetic dipole terms, or dipole from quadrupole terms, in the absorption spectrum. The technique is twice as sensitive as conventional measurements, functions at very low laser power, and reveals resonances that are invisible to existing spectroscopies. This approach could see application in analytical chemistry, condensed matter physics, nanotechnology, and forensic science.
[Phys. Rev. Applied 5, 014010] Published Wed Jan 27, 2016
]]>Massless Dirac fermions with a pseudospin of are tied to many intriguing properties of graphene. Previous studies have discussed the possibility of constructing a higher pseudospin system in artificial lattices of ultracold atoms, which can also support equally interesting physical properties. The authors of this paper demonstrate that photon transport in certain photonic crystals corresponds to a pseudospin-1 system. This is a significant development because, contrary to ultracold systems, photonic crystals offer a better opportunity to study novel pseudospin-1 physics in experimentally realizable materials and at room temperature.
[Phys. Rev. B 93, 035422] Published Thu Jan 14, 2016
]]>This paper provides a warning to the acoustic metamaterials community to be careful not to mistake the sign or value of the effective parameters, i.e. the density and modulus, of acoustic metamaterials for want of an overall picture of the physics involved. The authors here provide a new picture of the functioning of acoustic metamaterials based on hidden forces and hidden sources of volume. The new ansatz is tested on some established acoustic metamaterials with elements based on membranes, Helmholtz resonators, springs, and masses. It should provide the basis for a clearer vision of acoustic metamaterials and a faster route to real-world applications.
[Phys. Rev. B 93, 024302] Published Thu Jan 14, 2016
]]>Optical conformal mapping has been used to construct several isotropic devices with novel functionalities. In particular, a conformal cloak could confer omnidirectional invisibility. However, the maximum values of the refractive indexes needed for current designs are too large to implement, even in …
[Phys. Rev. B 93, 041406(R)] Published Wed Jan 06, 2016
]]>A new metamaterial acts like a cloak over a wide range of microwave frequencies.
[Phys. Rev. X 5, 041045] Published Fri Dec 18, 2015
]]>The ideal black body fully absorbs all incident rays, that is, all propagating waves created by arbitrary sources. A known idealized realization of the black body is the perfectly matched layer (PML), widely used in numerical electromagnetics. However, ideal black bodies and PMLs do not interact wit…
[Phys. Rev. B 92, 245402] Published Tue Dec 01, 2015
]]>Metamaterials researchers seek to build on past successes, such as cloaking, by adding control features to artificial electromagnetic media. This study presents a scheme whereby an active metamaterial featuring conventional structures plus a magnetically hard alloy can be “written” (much like the memory elements of a hard-disk drive) to tune its response in real time. The light-matter coupling between the constituents is also relevant to research in quantum information and magnon-based digital processing.
[Phys. Rev. Applied 4, 054015] Published Wed Nov 25, 2015
]]>Modulating the phase of electromagnetic waves has many applications in photonic research. A new mechanism allows a thin graphene metasurface to reliably achieve an extremely large phase modulation in THz radiation.
[Phys. Rev. X 5, 041027] Published Mon Nov 16, 2015
]]>The radiation dynamics of optical emitters can be manipulated by properly designed material structures modifying local density of photonic states, a phenomenon often referred to as the Purcell effect. Plasmonic nanorod metamaterials with hyperbolic dispersion of electromagnetic modes are believed to…
[Phys. Rev. B 92, 195127] Published Mon Nov 16, 2015
]]>Many of tomorrow’s photonic devices, including optical biosensors, may rely on light signals with highly particular polarization properties. A new experiment shows that an ultrathin layer of gold particles can selectively absorb or reflect a light beam depending on its polarization handedness.
[Phys. Rev. X 5, 041019] Published Wed Nov 04, 2015
]]>We demonstrate that use of the field effect enables tuning of the effective optical parameters of a layered hyperbolic metamaterial at optical frequencies. Field-effect gating electrically modulates the permittivity in transparent conductive oxides via changes in the carrier density. These permittiv…
[Phys. Rev. B 92, 184101] Published Mon Nov 02, 2015
]]>We theoretically investigate elastic waves propagating in metamaterials with simultaneous zero indices for both the longitudinal and transverse waves. With scattering objects (here cylinders) present in the metamaterial slabs, while the elastic waves can mostly transmit through the metamaterial slab…
[Phys. Rev. Lett. 115, 175502] Published Fri Oct 23, 2015
]]>Engineering collective excitations such as plasmons and polaritons provides access to exotic optical properties. This study reports semiconductor nanostructures with coupled surface modes that interact with multiple resonant dipoles, yielding double and triple polariton branches in the system’s response. This produces useful and tunable properties with the flexibility to enable low-voltage tunable filters, light-emitting diodes, and efficient nonlinear composite materials.
[Phys. Rev. Applied 4, 044011] Published Tue Oct 20, 2015
]]>Photonic and phononic systems use light and sound waves to produce a rich landscape of useful phenomena. The authors study model layered materials supporting tunable elastic surface waves that in many ways resemble surface plasmons. They also show that mechanical Bloch oscillations can be ascribed to the coupling of elastic guided modes of longitudinal and transverse vibrations in subsequent stacked plates. These findings not only give insight for mechanical sensors, actuators, and waveguides, but also suggest a means to explore basic condensed matter physics.
[Phys. Rev. Applied 4, 044012] Published Tue Oct 20, 2015
]]>We present a mechanism by which a metamaterial surface, or metasurface, can act as an ideal phase-controlled rotatable linear polarizer. Using coupled-mode theory and the idea of coherent perfect absorption into auxiliary polarization channels, we show how the losses and near-field couplings on the …
[Phys. Rev. A 92, 043826] Published Mon Oct 19, 2015
]]>Utilizing the notion of metamaterials, in recent years the concept of a circuit and lumped circuit elements have been extended to the optical domains, providing the paradigm of optical metatronics, i.e., metamaterial-inspired optical nanocircuitry, as a powerful tool for design and study of more com…
[Phys. Rev. B 92, 165413] Published Tue Oct 13, 2015
]]>We investigate the wave vector and frequency-dependent screening of the electric field in atomically thin (quasi-two-dimensional) crystals. For graphene and hexagonal boron nitride we find that, above a critical wave vector , the static permittivity becomes negative and the Kramers-…
[Phys. Rev. B 92, 161402(R)] Published Tue Oct 06, 2015
]]>Propagation of elastic waves in acoustic metamaterials based on locally resonant viscoelastic phononic crystals is discussed. A variational formulation of the complex band structure for in-plane polarized waves is proposed and used to formulate a finite element model. Two different types of locally …
[Phys. Rev. B 92, 104110] Published Wed Sep 30, 2015
]]>The generation of a second-harmonic wave, which is one typical nonlinear feature, is enhanced in a composite of plasma and metamaterial. When we generate plasma by an injection of microwaves, whose frequencies are fundamental, we observe intensified second-harmonic waves in the cases of negative-ref…
[Phys. Rev. E 92, 033105] Published Wed Sep 23, 2015
]]>Metasurfaces characterized by a transverse gradient of local impedance have recently opened exciting directions for light manipulation at the subwavelength scale. Here we add a temporal gradient to the picture, showing that spatiotemporal variations over a surface may greatly extend the degree of wa…
[Phys. Rev. B 92, 100304(R)] Published Tue Sep 22, 2015
]]>Nonlinear metasurfaces based on coupling a locally enhanced plasmonic response to intersubband transitions of -doped multi-quantum-wells (MQWs) can provide second-order susceptibilities orders of magnitude larger than any other nonlinear flat structure measured so far. Here we present a comprehensi…
[Phys. Rev. B 92, 125429] Published Mon Sep 21, 2015
]]>Metamaterials allow us to manipulate all aspects of a propagating wave (of light or sound) as it passes through a material, including its speed, direction, and amount of energy reflected or transmitted. The authors demonstrate a sonic-crystal lens that focuses underwater sound with control over these three aspects. This lens is acoustically transparent over a broad bandwidth, proving that high sound speeds and matched acoustic impedance can be simultaneously achieved in such a design, which offers progress in underwater and ultrasound applications that have been held back by material limitations.
[Phys. Rev. Applied 4, 034003] Published Tue Sep 15, 2015
]]>We realize a suppression of an electromagnetically-induced-transparency-like (EIT-like) transmission in a metasurface induced by a local electric field that is strongly enhanced based on two approaches: squeezing of electromagnetic energy in resonant metasurfaces and enhancement of electromagnetic e…
[Phys. Rev. B 92, 125124] Published Mon Sep 14, 2015
]]>We present a comprehensive theoretical study of the magnetic field dependence of the near-field radiative heat transfer (NFRHT) between two parallel plates. We show that when the plates are made of doped semiconductors, the near-field thermal radiation can be severely affected by the application of …
[Phys. Rev. B 92, 125418] Published Mon Sep 14, 2015
]]>Dispersion relations for acoustic and electromagnetic waves guided by resonant inclusions located at the surface of an elastic solid or an interface between two media are analyzed theoretically within the effective medium approximation. Oscillators on the surface of an elastic half-space are shown t…
[Phys. Rev. B 92, 115422] Published Mon Sep 14, 2015
]]>Spies and wizards, take note: The authors provide an overview of the recent efforts in metamaterial technology devoted to cloaking, as well as a perspective on the future of this rapidly changing field. The potential of passive cloaking techniques is outlined, as is the possibility of overcoming their limitations using active or nonlinear cloaks.
[Phys. Rev. Applied 4, 037001] Published Tue Sep 01, 2015
]]>As metamaterials research continues to evolve, we may consider effects and systems that go beyond the electric-dipole approximation. The authors fabricate an optical metasurface in which nanoscale artificial metamolecules exhibit a dominant electric-current quadrupolar response at visible wavelengths, and the optical reflection and absorption change considerably when the illumination direction is reversed. This bifacial metasurface could be applied in interferometric devices and coatings, solar cells, or directional optical elements such as light sources and detectors.
[Phys. Rev. Applied 4, 024019] Published Thu Aug 27, 2015
]]>In this paper, we study a topological phase transition in a wire medium operating at infrared frequencies. This transition occurs in the reciprocal space between the indefinite (open-surface) regime of the metamaterial and its dielectric (closed-surface) regime. Due to the spatial dispersion inheren…
[Phys. Rev. B 92, 075139] Published Wed Aug 26, 2015
]]>Electromagnetically induced transparency (EIT) has been extensively investigated in atomic systems, to control transmission through optical components and the velocities of “slow light” packets. The authors realize EIT using a metamaterial that turns transparent with the incidence of an auxiliary electromagnetic wave, in the same manner as from the original, atomic EIT effect. This approach could lead to applications including the storage of electromagnetic waves (the ultimate slowing of light) across a wide frequency range for optical computing.
[Phys. Rev. Applied 4, 024013] Published Fri Aug 21, 2015
]]>Manipulating sound waves is key in applications such as ultrasound imaging and nondestructive testing. To this end, the authors present an acoustic phased array using a metascreen that transmits sound energy from a single source and steers the outgoing wavefront in the desired direction. Significantly, this metascreen does not itself contain any source of sound, unlike a conventional phased array with many individual sources. This passive array is therefore notably appealing for its simplicity, low cost, and good acoustic performance.
[Phys. Rev. Applied 4, 024003] Published Thu Aug 06, 2015
]]>Incandescent sources typically emit broadband light in all directions. Most of this radiation is lost for applications in the infrared region, such as spectroscopy or compositional analysis. Here the authors control both the spatial and temporal coherence of blackbody radiation with a plasmonic metasurface that emits a narrow band of frequencies in a small solid angle. This system operates reliably at 600 °C using CMOS-compatible materials, inviting the development of compact, efficient, and cheap infrared sources and gas detectors.
[Phys. Rev. Applied 4, 014023] Published Thu Jul 30, 2015
]]>Inspired by helicity dependent optical phenomena in chiral metamaterials the authors exploit the idea of helicity degree of freedom of Dirac fermions. They perform a first-principles study of SnTe films and show that giant helicity splitting in the band structures can be induced under moderate electric field. They suggest using helicity as an extra degree of freedom for helicity-resolved filtering and focusing of Dirac fermions.
[Phys. Rev. B 92, 041408(R)] Published Tue Jul 21, 2015
]]>Rendering things invisible has turned out to be in the domain of science, not magic. The authors offer an approach to cloaking based on a simple conformal surface wrapped around the object of interest. Their theory shows that by covering the object with a stealth surface on the illuminated side, and a time-reversed version of the same surface on the shadowed side, one can realize ideal cloaking, independent of the size of the object, in a robust, broadband, ultrathin, and lossless technology.
[Phys. Rev. Applied 4, 014005] Published Thu Jul 16, 2015
]]>An array of helical elements absorbs radiation of a certain frequency while casting no shadow in light over a range of other frequencies.
[Phys. Rev. X 5, 031005] Published Tue Jul 14, 2015
]]>When wave effects of thermal photons become significant, thermal emitters can exhibit intriguing coherent effects. Here, we show that the superradiant emission, which was originally found in quantum emitters, can be realized in resonant thermal emitters. Similar to the superradiance in quantum emitt…
[Phys. Rev. B 92, 024302] Published Mon Jul 13, 2015
]]>A major limitation of current acoustic metamaterials is that their acoustic properties are either locked into place once fabricated or are only modestly tunable, tying them to the particular application for which they are designed. We present a design approach that yields active metamaterials whose …
[Phys. Rev. B 91, 220303(R)] Published Tue Jun 30, 2015
]]>Concepts from optics aimed at creating “invisibility cloaks” are being extended to acoustics for soundproofing and stealth technology, with the same goal of passing waves around an object with no perceptible perturbation. The authors employ transformation acoustics to design and demonstrate a broadband, three-dimensional cloak that renders an object in an open cavity with hard boundaries nearly undetectable. Their actual cloak is an acoustic metamaterial made simply of stacked sheets of common acrylic plastic, with millimeter-scale features.
[Phys. Rev. Applied 3, 064019] Published Fri Jun 26, 2015
]]>Porous metamaterials exhibit dramatic changes in their Hall voltage relative to their bulk material. Researchers theoretically investigate this result and suggest techniques for experimental verification.
[Phys. Rev. X 5, 021030] Published Mon Jun 22, 2015
]]>The surface states of topological insulators are protected from backscattering, making them a promising resource for computing and materials science. This topological protection is now demonstrated in a radio-frequency circuit.
[Phys. Rev. X 5, 021031] Published Mon Jun 22, 2015
]]>Technology to efficiently handle light in the terahertz range is sought for a wide range of applications, including nondestructive testing, medical diagnostics, and weapons detection. Liquid-crystal devices are cheap and promising, but currently suffer from high operating voltage and long response times. The authors exploit coupling between periodically arranged patch resonators and external fields to propose a low-voltage absorber whose reflectance can be modulated from nearly 0 to 90%, with switching times around 50 ms–a dramatic improvement over existing technology that stands to enable new, low-cost, highly tunable terahertz devices.
[Phys. Rev. Applied 3, 064007] Published Thu Jun 11, 2015
]]>We investigate the effect of parity-time (PT) symmetric optical potentials on the radiation of achiral and chiral dipole sources. Two properties unique to PT-symmetric potentials are observed. First, the dipole can be tuned to behave as a strong optical emitter or absorber based on the non-Hermitici…
[Phys. Rev. B 91, 245108] Published Fri Jun 05, 2015
]]>Electromagnetic scattering has applications in astrophysics, atmospheric science, and medical imaging. Researchers design a metamaterial that exhibits anomalously weak scattering over a band of optical frequencies.
[Phys. Rev. X 5, 021021] Published Fri May 29, 2015
]]>Radio-frequency metamaterials with negative magnetic response hold great promise for both reducing the size and improving the performance of antennas for wireless applications. Using temperature to modify the superfluid density in a three-dimensional superconducting metamaterial, the authors demonstrate continuous in situ tunability of the effective permeability, from negative to positive values, without resorting to lossy lumped elements.
[Phys. Rev. Applied 3, 054010] Published Thu May 28, 2015
]]>Optical metasurfaces have become a new paradigm for creating flat optical devices. While being typically an order of magnitude thinner than the wavelength of light, metasurfaces allow control of the phase of propagating light waves across the full range and therefore enable the realization of opt…
[Phys. Rev. B 91, 195401] Published Tue May 05, 2015
]]>Electromagnetic pulse propagation in a quantum metamaterial, an artificial, globally quantum coherent optical medium, is numerically simulated. We show that a one-dimensional quantum metamaterial based on superconducting quantum bits, initialized in an easily reachable factorized excited state, demo…
[Phys. Rev. B 91, 134513] Published Thu Apr 23, 2015
]]>We demonstrate an innovative multifunctional artificial material that combines exotic metamaterial properties and the environmentally responsive nature of phase-change media. The tunable metamaterial is designed with the aid of two interwoven coordinate-transformation equations and implemented with …
[Phys. Rev. B 91, 134105] Published Thu Apr 16, 2015
]]>[Phys. Rev. B 91, 159904] Published Mon Apr 13, 2015
]]>In addition to its extraordinary mechanical, thermal and electrical properties, graphene shows great potential in manipulating electromagnetic fields. One of the main advantages of graphene compared to other materials is the extraordinary tunability of its conductivity, which can be achieved electrically by means of a back gate, or optically through the excitation of photocarriers. Scientists from Belgium, Sweden and the United States demonstrate that this tunability of graphene can be used in a novel setup for the generation of frequency combs. Traditionally, frequency combs are generated using nonlinear materials. The researchers studied the interaction between light and time-dependent graphene sheets, including both dispersion and explicit time-dependence of the conductivity. Based on this model, they demonstrated that frequency combs can be generated without material nonlinearities. Indeed, at terahertz frequencies it is possible to modulate the linear, time-dependent conductivity of graphene to obtain a large variety of frequency combs.
[Phys. Rev. B 91, 161403(R)] Published Wed Apr 08, 2015
]]>We present a general method for retrieving the effective tensorial permittivity of uniaxially anisotropic metamaterials. By relaxing the usually imposed constraint of assuming nonmagnetic metal/dielectric metamaterials, we also retrieve the effective permeability tensor and show that multilayer hype…
[Phys. Rev. B 91, 155406] Published Tue Apr 07, 2015
]]>We demonstrate the photogeneration of loaded dipole plasmonic antennas resonating at THz frequencies. This is achieved by the patterned optical illumination of a semiconductor surface using a spatial light modulator. Our experimental results indicate the existence of capacitive and inductive couplin…
[Phys. Rev. B 91, 125443] Published Tue Mar 31, 2015
]]>Many biological structures, from macromolecules to proteins, as well as a number of solid-state systems including ferroelectric and ferro nano- and microstructures, possess static toroidal shapes. A theoretical study shows that the dynamic toroidal dipoles constructed from ionic crystals can be used to engineer metamaterials to control how electromagnetic radiation is scattered and transmitted.
[Phys. Rev. X 5, 011036] Published Fri Mar 27, 2015
]]>Concealing objects by making them invisible to an external electromagnetic probe is coined by the term “cloaking.” Cloaking devices, having numerous potential applications, are still facing challenges in realization, especially in the visible spectral range. In particular, inherent losses and extrem…
[Phys. Rev. B 91, 125426] Published Thu Mar 19, 2015
]]>In recent years we have learned to fabricate structures smaller than electromagnetic wavelengths, and to assemble them into metamaterials with exotic optical properties for previously unimaginable applications. One such property is perfect absorption of incident light, with no reflection or transmission, across many wavelengths. The authors review the physics, design principles, and classification of thin perfect absorbers, and outline avenues for progress.
[Phys. Rev. Applied 3, 037001] Published Tue Mar 17, 2015
]]>A mirror made with metamaterials reflects at a selected angle and only responds to radiation of a specific frequency, while being transparent to other radiation.
[Phys. Rev. Lett. 114, 095503] Published Fri Mar 06, 2015
]]>Photonic crystal and split ring resonator (SRR) metamaterial waveguides with Kerr nonlinear dielectric impurities are studied. The transmission coefficients for two guided modes of different frequencies scattering from the Kerr impurities are computed. The systems are shown to exhibit multiple trans…
[Phys. Rev. B 91, 085113] Published Thu Feb 19, 2015
]]>We propose a numerical and an experimental study of an invisibility carpet for linear water waves. In the first part, we introduce the concept of an invisibility carpet in the case of linear water waves and apply this concept for a bounded problem: a wavetank. In the second part, we study a simpler …
[Phys. Rev. E 91, 023010] Published Thu Feb 12, 2015
]]>Based on Mie scattering theory, we derive the complete dynamic polarizability tensor for circular, azimuthally symmetric cylinders excited by an arbitrary field distribution, and provide compact expressions for all of its elements. Our results comprise fully dynamic cylinder polarizabilities, improv…
[Phys. Rev. B 91, 085104] Published Fri Feb 06, 2015
]]>Regular lattices comprising superconducting quantum interference devices (SQUIDs) form magnetic metamaterials exhibiting extraordinary properties, including tunability, dynamic multistability, and negative magnetic permeability. The SQUIDs in a metamaterial interact through nonlocal, magnetic dipole…
[Phys. Rev. B 91, 054303] Published Tue Feb 03, 2015
]]>We propose a scheme to realize stable propagation of linear and nonlinear surface polaritons (SPs) by placing a four-level quantum emitters at the interface between a dielectric and a negative-index metamaterial (NIMM). We show that in linear propagation regime SPs can acquire an active Raman…
[Phys. Rev. A 91, 023803] Published Mon Feb 02, 2015
]]>Recently, the possibility of achieving one-way backscatter immune transportation of light by mimicking the topological properties of certain solid state systems, such as topological insulators, has received much attention. Thus far, however, demonstrations of nontrivial topology in photonics have re…
[Phys. Rev. Lett. 114, 037402] Published Thu Jan 22, 2015
]]>We study nonlinear properties of multilayer metamaterials created by graphene sheets separated by dielectric layers. We demonstrate that such structures can support localized nonlinear modes described by the discrete nonlinear Schrödinger equation and that its solutions are associated with stable di…
[Phys. Rev. B 91, 045424] Published Wed Jan 21, 2015
]]>We investigate the tunable and switchable optical radiators and metamaterials formed by metallic nanodipole antennas with submicroscopic gaps (1.2 nm), of which linear and third-order nonlinear quantum conductivities are observed due to the photon-assisted tunneling effect. The quantum conductivitie…
[Phys. Rev. B 91, 035426] Published Tue Jan 20, 2015
]]>