Metamaterial Layer Research Articles

Optical properties of a one-dimensional photonic crystal containing a graphene-based hyperbolic metamaterial defect layer

The transmission properties of a one-dimensional defective photonic crystal have been investigated using the transfer matrix method. A layer of graphene-based hyperbolic metamaterial whose optical axis is tilted with respect to the interface is taken as a defect. It is shown that two kinds of the defect modes can be found in the band gaps of the structure for TM-polarized waves. One kind is created at the frequency range in which the principle elements of the effective permittivity tensor of the defect layer have the same signs. The frequency of this kind of defect mode is independent from the orientation of the optical axis of the defect layer. The other one is created at the hyperbolic dispersion frequency range. Such a defect mode appears due to the anisotropic behavior of the defect layer and its frequency strongly depends on the orientation of the optical axis. Unlike the conventional defect modes, the magnetic field of this defect mode is localized around the defect layer.

Combination of artificial materials with conventional pyramidal absorbers for microwave absorption improvement

This article addresses the combination of an artificial and conventional absorber materials in order to enhance its absorption properties and compactness. We demonstrate an increase of the absorption performance of the pyramidal absorbers by integrating a metamaterial layer. The latter is composed of two unit cells with multi resonance behavior between 2GHz and 18GHz. The simulation results of the hybrid material predict absorption for normal and oblique incidence of the electromagnetic wave at low and high frequencies depending on the wave polarization.Hybrid materials (metamaterial+conventional pyramidal absorbers) have been achieved using two pyramidal absorbers; the first one is a commercial absorber APM12/SIEPEL and the second one is the same material but with reduced dimensions. These absorbers are made of polyurethane foam loaded with carbon particles. The measurements show an increase of the absorption performance compared to the pyramidal absorber alone, even for the absorber with reduced dimensions.

Tunable quasi-monochromatic near-field radiative heat transfer in s and p polarizations by a hyperbolic metamaterial layer

The spectra of thermal radiation have been controlled for thermophotovoltaics and mid-infrared light sources, and the spectral heat flux has been shown to exceed the blackbody limit by utilizing near-field coupling. We show that a hyperbolic metamaterial layer enables quasi-monochromatic near-field radiative heat transfer between a metallic emitter and a dielectric receiver. The quasi-monochromatic transfer originates from the Fabry-Perot resonance in the hyperbolic layer, where evanescent waves in the vacuum gap become propagative. The Fabry-Perot resonance is excited in s and p polarizations, and the resonant condition is almost independent of the lateral wavenumber due to the large effective parallel permittivity of the hyperbolic metamaterial. The resonant frequency is tuned by the volume filling fraction and the thickness of the layer, while the frequency misalignment between polarizations is kept small. Furthermore, the resonant frequency is shown to be robust to the fluctuation of the gap width and the refractive index of the receiver dielectrics. The hyperbolic metamaterial layer is applied to near-field thermophotovoltaic energy generation, and both the power output and the efficiency are enhanced simultaneously. Numerical simulation reveals that the hyperbolic metamaterial layer can be realized by a hexagonal cylinder array.

Dispersion of electromagnetic waves in layered graphene-dielectric metamaterials

 In this paper possibility of creating a medium based on graphene-dielectric (quartz) structures with a hyperbolic shape of the dispersion relation is considered. Using the Bloch theorem and the transfer matrix method, dispersion relations are found for hyperbolic media, consisting of periodically located layers of graphene and a dielectric. The transfer matrix method gives the possibility to relate the amplitudes of the incident and reflected electromagnetic waves at the input to the layered structure with the amplitudes at the output by means of propagation and transfer matrixes. The frequency dependent optical conductivity of graphene sheet is calculated by Kubo formula which takes into account both interband and intraband transitions. It is shown that when the chemical potential of graphene is increased, the elliptic form of the dispersion curve turns into to hyperbolic. This result is due to the fact that the perpendicular component of the permittivity changes its sign when the chemical potential is changed.

Experiments on the low frequency barrier characteristics of cellular metamaterial panels in a diffuse sound field.

The metamaterial under investigation here consists of a periodic arrangement of unit plates in a grid-like frame such that there is a contrast in the local areal mass between cell interior and cell wall. In the low frequency range and under normal incidence this metamaterial panel exhibits a sound transmission loss significantly larger than the transmission loss of an unstructured panel with the same homogeneous mass per unit area. However, when the incident sound field is diffuse, the relative advantage of the metamaterial barrier is reduced or eliminated. A sequence of experiments is documented to demonstrate that the relative advantage of the metamaterial barrier can be realized even in a diffuse sound field by creating a hybrid barrier system which embeds the metamaterial layer between a normalizing waveguide layer on the incident side and an absorbing layer on the transmitted side. The sound normalizing waveguide layer is a lattice structure, and the absorbing layer is high performance glass fiber mat. By using measurements of the transmission loss of a 1.2 m square panel system the role of each of these components is demonstrated.

Experimental Investigations of Quasi-flat Acoustic Absorbers Enhanced by Metamaterial Layers

Experimental Investigations of Quasi-flat Acoustic Absorbers Enhanced by Metamaterial Layers

Photonic band gap spectra in Octonacci metamaterial quasicrystals

In this work we study theoretically the photonic band gap spectra for a one-dimensional quasicrystal made up of SiO2 (layer A) and a metamaterial (layer B) organized following the Octonacci sequence, where its nth-stage Sn is given by the inflation rule Sn=Sn−1Sn−2Sn−1 for n≥3, with initial conditions S1=A and S2=B. The metamaterial is characterized by a frequency dependent electric permittivity ε(ω) and magnetic permeability μ(ω). The polariton dispersion relation is obtained analytically by employing a theoretical calculation based on a transfer-matrix approach. A quantitative analysis of the spectra is then discussed, stressing the distribution of the allowed photonic band widths for high generations of the Octonacci structure, which depict a self-similar scaling property behavior, with a power law depending on the common in-plane wavevector kx.

Time domain characteristics of wave motion in dispersive and anisotropic continuum acoustic metamaterials.

The authors study the wave propagation in continuum acoustic metamaterials whose all or not all of the principal elements of the mass tensor or the scalar compressibility can be negative due to wave dispersion. Their time-domain wave characteristics are particularly investigated by the finite-difference time-domain (FDTD) method, in which algorithms for the Drude and Lorentz dispersion pertinent to acoustic metamaterials are provided necessarily. Wave propagation nature of anisotropic acoustic metamaterials with all admissible material parameters are analyzed in a general manner. It is found that anomalous negative refraction phenomena can appear in several dispersion regimes, and their unique time-domain signatures have been discovered by the FDTD modeling. It is further proposed that two different metamaterial layers with specially assigned dispersions could comprise a conjugate pair that permits wave propagation only at specific points in the wave vector space. The time-domain pulse simulation verifies that acoustic directive radiation capable of modulating radiation angle with the wave frequency can be realized with this conjugate pair. The study provides the detailed analysis of wave propagation in anisotropic and dispersive acoustic mediums, which makes a further step toward dispersion engineering and transient wave control through acoustic metamaterials.

Multiple Re-Reflections and Focusing of Waves by a Metamaterial Layer

Multiple Re-Reflections and Focusing of Waves by a Metamaterial Layer

Theoretical investigation of guided modes in planar waveguides having chiral negative index metamaterial core layer

In this work, a slab waveguide consisting of a chiral negative index metamaterial film surrounded by a dielectric medium was considered. The characteristics of both even and odd guided modes are investigated. The field profile, dispersion curves and power distribution for these configurations are also studied. A set of novel features were observed such as negative power in the chiral film and the existence of normalized frequencies less than the cutoff at which waves can propagate.

Octonacci photonic crystals with negative refraction index materials

We investigate the optical transmission spectra for s-polarized (TE) and p-polarized (TM) waves in one-dimensional photonic quasicrystals on a quasiperiodic multilayer structure made up by alternate layers of SiO2 and metamaterials, organized by following the Octonacci sequence. Maxwell's equations and the transfer-matrix technique are used to derive the transmission spectra for the propagation of normally and obliquely incident optical fields. We assume Drude-Lorentz-type dispersive response for the dielectric permittivity and magnetic permeability of the metamaterials. For normally incident waves, we observe that the spectra does not have self-similar behavior or mirror symmetry and it also features the absence of optical band gap. Also for normally incident waves, we show regions of full transmittance when the incident angle θC = 0° in a particular frequency range.

Spin Hall effect of transmitted light in a three-layer waveguide with lossy epsilon-near-zero metamaterial.

We study spin Hall effect (SHE) of transmitted light in a three-layer waveguide with epsilon-near-zero (ENZ) metamaterial. As the increased loss of anisotropic ENZ metamaterial brings decreased propagation loss for oblique incidence, the transmission of incident light is enhanced which induces a different distribution of transverse shift peaks. Based on simulation results, the influences of ENZ permittivity components and thickness as well as gold layer thickness on transverse shift of left-circularly polarized light in ENZ/Au/ENZ waveguide are analyzed. In order to make our results convincing we make use of alternating thin layers of silver and germanium stacking to construct anisotropic ENZ metamaterial. The transverse shifts of incident light with different ENZ metamaterial and gold layer thicknesses are obtained. Calculation results show the maximum transverse shifts of left-polarized light for linear polarized light can achieve 49.6 microns. Meanwhile, the enhanced SHE of transmitted light is invariant with the variation of gold layer which shows a great tolerance to fabrication error.

Plasma metamaterials as cloaking and nonlinear media

Plasma metamaterials, composites of low-temperature plasmas and periodic functional microstructures, work as cloaking and nonlinear media. Due to functions of the microstructures like negative permeability, electromagnetic waves in and around plasma metamaterials propagate in a quite different manner from the case with the conventional space in which relative permeability is positive and unity. Using plasmas and plasma metamaterials, we achieve various controls of microwave propagating paths such as unidirectionality and cloaking in the two- or 3D spaces. For instance, a concentric plasma layer makes wave propagation unidirectional, and waves propagate in different routes when they start inside or outside the concentric layer. Furthermore, due to spatial permittivity gradient and anisotropic refractive index, electromagnetic waves detour in plasma metamaterial layers. Another significant point that plasma metamaterials can realize is nonlinearity. When we study high-power electromagnetic waves propagating in them, we observe several properties describable in terms of nonlinear dynamics and nonlinear photonics. Microwaves beyond threshold energy trigger bifurcations in plasma permittivity, and the second harmonic wave detected simultaneously is generated with strong emission levels. Such electromagnetic wave propagation is achieved with advantages over other materials, since plasmas and metallic microstructures work in harmony and in synergy.

Periodic Imbert-Fedrov shift in a prism-coupling waveguide with epsilon-near-zero metamaterial

We study the periodic Imbert-Fedrov (IF) shift in a prism-coupling waveguide with epsilon-near-zero (ENZ) metamaterial. We take into account the influence of ENZ metamaterial and gold layer thicknesses as well as the metal material on the IF effect in our proposed waveguide. The calculation method is derived and theoretical analysis is given. Based on simulation results, we can find periodic IF shifts can be observed which provides us an opportunity to realize enhanced IF effect at various incident angle. Further calculations shows that ENZ metamaterial thickness determines the maximum IF shift value, the periodic property and incident angle corresponding to IF shift peak. However, the metal thickness and permittivity only has an important influence on maximum IF shift value which will not affect the periodic property and incident angle corresponding to IF shift peak.

Traveling Lamb wave in elastic metamaterial layer

The propagation of traveling Lamb wave in single layer of elastic metamaterial is investigated in this paper. We first categorized the traveling Lamb wave modes inside an elastic metamaterial layer according to different combinations (positive or negative) of effective medium parameters. Then the impacts of the frequency dependence of effective parameters on dispersion characteristics of traveling Lamb wave were studied. Distinct differences could be observed when comparing the traveling Lamb wave along an elastic metamaterial layer with one inside the traditional elastic layer. We further examined in detail the traveling Lamb wave mode supported in elastic metamaterial layer, when the effective P and S wave velocities were simultaneously imaginary. It was found that the effective modulus ratio is the key factor for the existence of special traveling wave mode, and the main results were verified by FEM simulations from two levels: the level of effective medium and the level of microstructure unit cell.

Microwave birefringent metamaterials for polarization conversion based on spoof surface plasmon polariton modes.

We propose the design of wideband birefringent metamaterials based on spoof surface plasmon polaritons (SSPPs). Spatial k-dispersion design of SSPP modes in metamaterials is adopted to achieve high-efficiency transmission of electromagnetic waves through the metamaterial layer. By anisotropic design, the transmission phase accumulation in metamaterials can be independently modulated for x- and y-polarized components of incident waves. Since the dispersion curve of SSPPs is nonlinear, frequency-dependent phase differences can be obtained between the two orthogonal components of transmitted waves. As an example, we demonstrate a microwave birefringent metamaterials composed of fishbone structures. The full-polarization-state conversions on the zero-longitude line of Poincaré sphere can be fulfilled twice in 6–20 GHz for both linearly polarized (LP) and circularly polarized (CP) waves incidence. Besides, at a given frequency, the full-polarization-state conversion can be achieved by changing the polarization angle of the incident LP waves. Both the simulation and experiment results verify the high-efficiency polarization conversion functions of the birefringent metamaterial, including circular-to-circular, circular-to-linear(linear-to-circular), linear-to-linear polarization conversions.

Analysis of Reflectance Properties in 1D Photonic Crystal Containing Metamaterial and High-Temperature Superconductor

In the present work, reflectance properties of one-dimensional photonic crystal (1D PC) containing a metamaterial and high-temperature superconductor have been investigated theoretically and analyzed. The reflectance/transmittance spectrum of the proposed structure is obtained by using the characteristic or transfer-matrix method (TMM). The results show that by increasing the thickness of the metamaterial layer, the width of the second reflection band decreases while the width of the first reflection band remains almost the same though it shifts towards the higher frequency side. In addition to this, a new band gap arises in the lower side of frequency. But, when the thickness of the superconductor layer is increased, the width of both the bands increases and no additional band arises in this case. Moreover, the reflection band is also affected by varying the operating temperature of the superconducting layer and the results show that bands get narrower by increasing the operating temperature. Finally, the effect of incident angle on the reflection band has been discussed for both transverse electric (TE) and transverse magnetic (TM) polarizations.

A universal design to realize a tunable perfect absorber from infrared to microwaves.

We propose a design for an universal absorber, characterized by a resonance frequency that can be tuned from visible to microwave frequencies independently of the choice of the metal and the dielectrics involved. An almost perfect absorption up to 99.8% is demonstrated at resonance for all polarization states of light and for a very wide angular aperture. These properties originate from a magnetic Fabry-Perot mode that is confined in a dielectric spacer of λ/100 thickness by a metamaterial layer and a mirror. An extraordinary large funneling through nano-slits explains how light can be trapped in the structure. Simple scaling laws can be used as a recipe to design ultra-thin perfect absorbers whatever the materials and the desired resonance wavelength, making our design truly universal.

Analysis of Novel Class of Surface Plasmon Phenomena Having a Metamaterial Layer Between Two Different Metals for Sensor Application

This paper includes a brief introduction on surface plasmon resonance’s (SPRs) theory, principle, and application, followed by describing the utility of metamaterials for this sensing paradigm. The bimetallic layers of gold and silver are crucial for SPR sensing, which is detailed. Finally, the matrix method for the calculation of reflectance for multiple layers is explained. The structures along with the corresponding graphs are discussed, including what happens when a metamaterial is used between two metal layers is derived.

Multilayer solar cell waveguide structures containing metamaterials

Multilayer antireflection coating structures made from silicon and metamaterials are designed and investigated using the Transfer Matrix Method (TMM). The Transfer Matrix Method is a very useful algorithm for the analysis of periodic structures. We investigate in this paper two anti-reflection coating structures for silicon solar cells with a metamaterial film layer. In the first structure, the metamaterial film layer is sandwiched between a semi-infinite glass cover layer and a semi-infinite silicon substrate layer. The second structure consists of a four layers, a pair of metamaterial-dielectric layer with opposite real part of refractive indices, is placed between the two semi-infinite cover and substrate.We have simulated the absorptivity property of the structures for adjustable thicknesses by using MAPLE software. The absorptivity of the structures achieves greater than 80% for incident electromagnetic wave of transverse magnetic (TM) polarization.