Metamaterial Layer Research Articles

Layered metamaterials with Sierpinski triangular fractal metasurface: Compatible stealth for S-band radar and infrared

Due to the completely opposite stealth mechanisms of radar and infrared waves, and the limitation of the Planck–Rozanov limit, compatible stealth of S-band radar and infrared is extremely difficult to realize at thin thicknesses. In order to solve the problem, a layered metamaterial consisting of infrared stealth layer (IRSL) with aluminum foil and radar stealth layer (RASL) with carbonyl iron powder is designed. The excellent infrared stealth performance (infrared emissivity < 0.3) is achieved because of the low infrared emissivity aluminum foil and reasonable area design. Meanwhile, the Sierpinski triangular fractal structure of IRSL not only serves to reduce the reflection of radar waves, but also introduces the electromagnetic double resonance mechanism of one-dimensional electric resonance and two-dimensional magnetic resonance to lose waves. Therefore, the effective absorption (RL < −10 dB) of 2.12–3.5 GHz in S-band is achieved with a thickness of only 2.24 mm. The double-layer model with fractal structure in this work realizes the perfect compatible stealth for S-band radar and infrared at extremely thin thickness, which provides a new design idea for the development of multi-band compatible stealth.

Ultra-broadband low-frequency high-efficiency acoustic energy harvesting with metamaterial-enhanced loudspeakers

Acoustic energy harvesters (AEHs) open up opportunities to recycle noise waste and generate electricity. They provide potential power solutions to a wide range of sensors. However, the practicality of AEHs has long been limited by their narrow bandwidths and low efficiencies. In this study, we present an ultra-broadband AEH and a highly efficient AEH that transforms sound energy into usable electrical power. Our broadband device comprises an electrodynamic loudspeaker driver and an optimized acoustic metamaterial matching layer and is capable of converting 7.6% to 15.1% of total incident sound energy from 50 to 228 Hz. Moreover, we demonstrate that by replacing the loudspeaker surround with a lower-loss material such as PDMS, the energy conversion rate can be significantly increased to 67%. The proposed broadband AEH has a fractional bandwidth eight times the state-of-the-art, while the proposed highly efficient AEH has a peak efficiency three times the state-of-the-art. The outstanding performance makes our designs cost-effective and scalable solutions for noise reduction and power generation.

Optimal design of Multiresonant Layered Acoustic Metamaterials (MLAM) via a homogenization approach

Broadband sound attenuation at low frequency ranges (below 500 Hz) has been a challenge in the acoustics field which cannot be solved, via conventional materials, unless impractical amounts of mass are employed. Multiresonant Layered Acoustic Metamaterials (MLAM) offer exceptional attenuating properties at lower frequencies, through novel coupled resonances mechanisms, in a layered configuration that make them amenable for large-scale manufacturing. To show the potential capabilities of MLAM, a novel computational design strategy has been developed to optimize the metamaterials’ performance in terms of their Sound Transmission Loss (STL). First, a multiscale homogenization framework specifically derived for MLAM allows an accurate and extremely fast evaluation of their STL response to normal-incidence acoustic waves in the frequency range of interest. Then, the MLAM design is parameterized into a set of relevant geometric features, which are optimized by means of an optimization scheme based on standard genetic algorithms combined with the homogenization model. The results demonstrate how this design strategy is a powerful tool to obtain optimal MLAM panel designs subject to constraints imposed by the application, for instance, in terms of weight or thickness of the panel, or the manufacturing process (e.g. geometric tolerances).

Geometric nonlinear analysis of dielectric layer based on concave paper-cut structure with zero Poisson’s ratio

When the sensor works in a limited environment, its accuracy is easily affected by unnecessary strain loss. The key to improve accuracy is to reduce the transverse strain of the dielectric layer structure. It is an innovative technology to construct zero Poisson’s ratio dielectric layer to limit the lateral strain of dielectric layer under normal pressure. The porous metamaterial dielectric layer with zero Poisson’s ratio is constructed based on the paper-cutting theory. The equivalent nonlinear mechanical model is established by use of Bernoulli Euler beam theory and energy method. The analytical expressions of equivalent Poisson’s ratio and equivalent Young’s modulus are given, and the necessity of considering geometric nonlinear large deformation is revealed. An improved variable step iterative method is proposed in order to solve the problem of equivalent internal force analysis caused by geometric deformation nonlinearity. The key of this method is to determine the displacement at the free end under the premise of considering the nonlinear superposition of the rigid body motion of the curved bar of the metamaterial. Based on the equivalent nonlinear mechanical model, the structural deformation characteristics of the dielectric layer structure in the linear small deformation stage and the nonlinear large deformation stage are analyzed. The results of theoretical, finite element simulation and experimental research reveal the necessity of considering geometric nonlinear factors in the practical application of the structure, which means that the foundation is theoretically and experimentally laid for the design of porous elastic dielectric layer of flexible capacitive pressure sensor.

Design of a novel graphene buzzle metamaterial refractometer for sensing of cancerous cells in the terahertz regime

This paper introduces a novel biosensor with enhanced sensitivity for detecting the dielectric constant. The biosensor utilizes a metamaterial buzzle resonator incorporated with a thin graphene layer measuring 35 nm, operating in the terahertz (THz) frequency range. The biosensor demonstrates remarkable performance, featuring a high average sensitivity of 495 GHz/RIU (7.64 dB/RIU) and a quality factor of 82. These attributes enable the biosensor to effectively differentiate between various types of cancer cells, including basal cell, breast cell, and cervical cell, Jurkat, MCF-7, and PC12. The biosensor's resonance frequency and peak attenuation (S11 dB) display considerable sensitivity to changes in the refractive index of the sample, thereby achieving excellent linear performance. As a result of developing these characteristics, the biosensor demonstrates to be highly effective in detecting and distinguishing cancer cells built on their dielectric properties. The sensor's sensitivity, combined with its capacity to distinguish between different cell types, makes it a promising tool for cancer finding and characterization. This Research presents a state-of-the-art biosensor capable of detecting the dielectric constant with remarkable sensitivity. This utilization of a metamaterial buzzle resonator and thin graphene layer in the THz regime, coupled with high average sensitivity, quality factor, and linear performance, enables effective discrimination of various cancer cell types. This biosensor holds great potential for advancing cancer detection and characterization techniques.

Enhanced Goos–Hänchen shifts for cross-polarization in the metamaterials containing chiral media and graphene

The cross-polarization Goos–Hänchen (GH) shifts of reflected wave from the symmetric layered metamaterials consisting of isotropic chiral media and graphene have been investigated. The influences of the physical parameters of chiral layers and graphene on the cross-polarization GH shifts for p polarized wave are discussed in detail. It is found that by adding graphene in the metamaterials, and only monolayer graphene needed, the cross-polarization GH shifts will be greatly enhanced. Meanwhile, extremely large cross-polarization GH shifts close to the Brewster angles will be obtained as a reasonable smaller chemical potential of the graphene is selected. Additionally, by adjusting the thickness and the chirality of the chiral material, the cross-polarization GH shifts can be enhanced with positive and negative peaks at different Brewster angles.

Absorption Properties of a One‐Dimensional Photonic Crystal with a Defect Layer Composed of a Left‐Handed Metamaterial and Two Monolayer Graphene

To construct photodetector and photovoltaic devices, light absorption is crucial. Herein, the absorption properties of a photonic crystal (PhC) consisting of high‐ and low‐index dielectric materials and a metamaterial defect layer are investigated. Two graphene sheets are assumed to surround the metamaterial layer. The study is theoretically investigated and numerically simulated in the gigahertz region. The metamaterial negative permittivity and permeability are assumed to follow the Drude model. The number of unit cells, graphene chemical potential (GCP), graphene phenomenological scattering rate (GPSR), and the metamaterial layer thickness are varied to examine the PhC tunable absorption properties. The following points are demonstrated: 1) the number of absorbance peaks increases as the number of unit cells increases; 2) when the GCP increases, the absorbance peaks dramatically decay; 3) the number of absorbance peaks in the absorption spectrum is independent of the GCP and GPSR; and 4) the absorbance peaks exhibit a significant enhancement with increasing GPSR. The proposed PhC can be used to design optical devices based on graphene and metamaterials, such as sensors, filters, and absorbers in the GHz range.

Scattering of Laguerre–Gaussian Beam by a Topological Insulator Cylinder Coated with Metamaterials

A theoretical investigation is presented to study the orbital angular momentum (OAM) beam scattering from a topological insulator (TI) cylinder coated with metamaterials. To calculate the electromagnetic (EM) response of the scattered field, the field equations are modified using Laguerre–Gaussian (LG) potential and plane wave scattering. The response of the metamaterial coated geometry has been reported for Double positive (DPS), Double negative (DNG), Epsilon negative (ENG), and Mu negative (MNG) coating layers, respectively. The normalized bistatic echo widths for the TI cylinder also change by changing the topological charge ( $$l$$ ), the radius of the metamaterial coated layer $$(b)$$ , source frequency $$(f)$$ , and beam waist radius $$({w}_{0})$$ . Our result for $${LG}_{00}$$ beam exactly tones with plane wave scattering as a reference. Numerical results in the form of bistatic echo widths have been calculated. Besides, the prementioned parameters, the influence of OAM mode index on the bistatic echo width is also analyzed. It can be seen that OAM mode number plays major role in controlling the scattering amplitude and intensity.

Investigation of reflections of terahertz waves from an inhomogeneous planar layer of a chiral metamaterial with allowance for frequency dispersion

The main purpose of this work is to develop a method for calculating the reflections of linearly polarized waves from an inhomogeneous planar layer of a chiral metamaterial. A mathematical model of a homogeneous inhomogeneous chiral medium is considered taking into account the frequency dispersion of material parameters. The moduli of the reflection coefficients of the main and cross-polarized field components from an inhomogeneous layer with parabolic and linear profiles of changes in the resonant frequency of a chiral metamaterial are calculated. It is shown that inhomogeneous planar structures of chiral metamaterials can significantly reduce the level of reflection of cross-polarized waves in the optical and terahertz ranges.

Parametric analysis of epsilon-negative (ENG) and near zero refractive index (NZRI) characteristics of extraordinary metamaterial for 5g millimetre-wave applications

A tuneable single layer metamaterial (MTM) unit cell comprised of symmetric H-shaped resonators for 5G applications is proposed with epsilon negative (ENG) between 28 - 32 GHz, near zero permeability along the entire frequency range, and near zero refractive index between 28 - 32 GHz. The constructed design offers wide operational frequency range of 24.6 - 31.8 GHz with transmission coefficient resonances (S21) at 28 GHz. The symmetric resonating patch is partitioned into four comparable and equal quartiles, with an H-shaped resonator in each quartile. The metamaterial copper metallic layer is constructed on a Rogers (RT-5880) substrate and has dimensions of 9 × 9 mm2. The scattering parameter for the interaction with the electromagnetic wave is introduced the interesting properties of the effective parameter. The compactness of the subwavelength based metal-dielectric based resonator is related to the tailored metallic design. Numerical simulation of the proposed design is executed in CST microwave studio.

An efficient underwater absorber using pentamode metamaterials for broadband frequency

To further design and develop broadband and efficient underwater sound absorption structure, we propose a hybrid acoustic structure composed of a rubber matrix layer, cylindrical cavity, pentamode metamaterial (PM) layer, impedance matching layer, and steel backing plate. Thanks to the special properties of the PMs, the hybrid acoustic structure obtains excellent broadband sound absorption performance (SAP) in the frequency range of 500–10000 Hz than that of the traditional cavity acoustic structure. To this end, we study the design principle of PM structure and its metal–water characteristics and analyze the sound absorption mechanism at the working frequency. In addition, the research shows that the material and geometric parameters of the structure have a significant impact on the SAP. By the optimization of structural material parameters, the average absorption coefficient at 500–10000 Hz can further increase to above 0.781. Finally, we also demonstrate that the structure still has good SAP under a wide range of oblique incidence angles. The research in this paper opens up bright perspectives for the design of underwater anechoic coatings for multifunctional applications.

EFFICIENCY ENHANCEMENT OF PHOTOVOLTAIC SOLAR CELLS USING METAMATERIALS ABSORBING SCREEN

This paper proposes a novel technique for the efficiency enhancement of photovoltaic (PV) solar cells using metamaterials absorbing screens. This kind of engineered material comprises resonant metallic rings that are printed on a host low-loss dielectric substance and made periodic in a two-dimensional lattice. The absorbing screen has been carefully designed, and its retrieved effective constitutive parameters, effective electric permittivity ϵeff and effective magnetic permeability µeff, are integrated within a numerically modelled amorphous-Silicon-based PV solar cell structure as an impedance matching layer. Such arrangement will greatly achieve matching between the effective impedance of the composite solar cell structure and free-space impedance and will result in higher photons absorption through the metamaterials anti-reflective screen. Numerical full-wave electromagnetic simulations are carried out using CST Microwave Studio for the design of a metamaterial absorbing screen. Due to the large computational resources required, COMSOL Multiphysics was adopted in the design and analysis of the composite structure comprising a two-dimensional PV solar cells layer. Based on the numerical results, both optical and electric characteristics of the PV solar cell structure were enhanced with the use of a metamaterial layer. Moreover, efficiency enhancement by 5% was permissible, in which efficiency reached 12% with the use of metamaterials as compared to the efficiency of the classical PV cells of 7%. The obtained results are very promising, and the potential integration of metamaterials in commercial PV solar cells will show significant advancement in efficiency enhancement of PV cells and realization of smart PV solar cells with the consideration of additional features from metamaterials.

Two-beam interferometry with a definitive phase-shift sign

Subject of study. The shift direction of interference fringes depending on the sign of the local phase shift introduced to one of the interfering waves was investigated in terms of two-beam interferometry. Aim of study. This study aimed to validate the fact that two-beam interferometry based on a single interferogram enables definitive determination of the phase-shift sign using the shift direction of the interference fringe. Method. Positions of the interference fringes and their shifts were calculated considering the phase distribution of interfering waves in the observation plane. The Mach–Zehnder interferometer was used to experimentally confirm the obtained theoretical results. Two closely adjacent substrates were used as objects. A subwavelength layer of a standard material was deposited on a part of the surface of one substrate, and a layer of metamaterial was deposited on the part of the second substrate. Main results. Expressions determining the direction and amplitude of the shift of interference fringes depending on the sign and amplitude of the local phase shift in one of the two interfering waves with a plane or spherical front were obtained. Strict rules of interference fringe shift depending on the sign of the phase shift were formulated based on the calculations. Results of the experiment using the Mach–Zehnder interferometer with different combinations of beams with spherical and plane wavefronts confirmed the theoretical calculations. Practical significance. Classic interferometric methods require significant time and the application of complex experimental procedures to determine the sign of the phase shift. The application of the results obtained in this study enables the determination of the sign of the introduced local phase shift based on a single interferogram without additional time expenditures. Thus, the method investigating the metamaterial layers of a subwavelength thickness is significantly simplified.

Investigation of the electromagnetic properties of a transverse insert based on a planar layer of a chiral metamaterial in a rectangular waveguide

The paper considers the solution of the problem of diffraction of the fundamental wave of a rectangular waveguide H10 on a planar transverse insert based on a chiral metamaterial created on the thin-wire conducting helices. To describe the chiral layer, a particular mathematical model is constructed that takes into account the properties of heterogeneity and dispersion of the permittivity and the chirality parameter of the artificial media. The well-known in physics model of Maxwell Garnett was used to take into account the heterogeneity property. To take into account the permittivity dispersion the Drude–Lorentz formula was applied and for the chirality parameter was used the Condon formula. The problem of diffraction of the rectangular waveguide main wave on a planar layer of a chiral metamaterial was solved by the partial regions method and was reduced to a system of linear algebraic equations for unknown reflection and transmission coefficients. It is shown that in the presence of a transverse chiral layer in the waveguide structure, a wave of the H01 type cross-polarized with respect to the main one arises. An analysis of the frequency dependences of the moduli of the reflection and transmission coefficients of the fundamental H10 and cross-polarized H01 showed that in some narrow frequency intervals in the single-mode gap, situations arise when the fundamental wave type is replaced from H10 to H01 near resonant frequencies. The transmission line under consideration can find application in the creation of frequency selective filters and polarization converters in the microwave range.

Buckling analysis of super-light composite cylinders with auxetic core and isotropic facing sheets with variable thickness: An analytical approach

An analytical method is presented to determine the axial buckling load of composite cylindrical shells with honeycomb core layer and nonuniform thickness using the first-order shear deformation theory, the nonlinear von Karman theory, and the Hooke law relations. The composite shell consists of two isotropic inner and outer layers with non-uniform thicknesses and one honeycomb core with constant thicknesses and adjustable Poisson's ratio. The equilibrium equations are a system of nonlinear differential equations with variable coefficients, and they are derived by employing the virtual work principle. The equilibrium equations have been solved analytically using the matched asymptotic expansion method of the perturbation technique. The stability equations extracted using the adjacent criterion include a system of linear homogenous equations with variable coefficients. By solving these equations, the buckling load is obtained analytically. A parametric study investigates the effects of different geometrical and mechanical parameters such as the honeycomb structure on the buckling load. The metamaterial honeycomb core layer has an adjustable Poisson's ratio, and the effect of negative/positive Poisson's ratio has been studied on the buckling behavior. The accuracy of the presented method is studied by comparing the results with the finite element method and some other references in special cases.

A Wideband Circularly Polarized Antenna Based on Anisotropic Metamaterial

This article presents a novel circularly polarized (CP) antenna based on an anisotropic metamaterial. The antenna is capable of performing linear-to-circular polarization conversion over a wideband of frequencies in the X-band (8–12 GHz). The proposed antenna was constructed from a metamaterial-based polarizer mounted above the aperture of a rectangular waveguide. The polarizer was oriented at 45° to E-plane of the waveguide. The proposed polarizer is composed of multiple metamaterial layers. The unit cell of the proposed polarizer consists of a single dielectric slab incorporating a series of rectangular split ring resonators that are printed on both sides of the slab. Impedance matching layers (IML) are introduced to enhance the axial-ratio (AR) bandwidth. The polarizer has a low profile in terms of electrical length (thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.41 \lambda _{0}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength at 10.5 GHz). A full-wave electromagnetic simulator was used to verify the anisotropic characteristics of the unit cell. This was achieved by showing that the metamaterial exhibits two different refractive indices along the orthogonal components of the incident electric field. The prototype of the proposed design is fabricated and measured to validate the performance. The measured results agree with the simulated ones and demonstrated a wide impedance bandwidth of 62.4% ranging from 7.08 to 13.5 GHz with a 3 dB AR bandwidth of 29.9% (9.25–12.5 GHz).

Wide-angle high-efficiency absorption of graphene empowered by an angle-insensitive Tamm plasmon polariton.

In recent years, researchers utilized Tamm plasmon polaritons (TPPs) in conventional heterostructures composed of a metal layer, a dielectric spacer layer and an all-dielectric one-dimensional (1-D) photonic crystal (PhC) to achieve high-efficiency absorption of graphene. According to the Bragg scattering theory, photonic bandgaps (PBGs) in all-dielectric 1-D PhC strongly shift toward shorter wavelengths (i.e., blueshift) as the incident angle increases. Therefore, TPPs in conventional heterostructures also show strongly blueshift property. Such strongly blueshift property of TPPs greatly limits the operating angle range of the high-efficiency absorption of graphene. Herein, we realize an angle-insensitive TPP in a heterostructure composed of a metal layer, a dielectric spacer layer and a 1-D PhC containing hyperbolic metamaterial layers. Empowered by the angle-insensitive property of the TPP, we achieve wide-angle high-efficiency absorption of graphene. The operating angle range (A > 80%) reaches 41.8 degrees, which is much larger than those in the reported works based on TPPs and defect modes. Our work provides a viable route to designing cloaking devices and photodetectors.

Quantum Optical Effective-Medium Theory for Layered Metamaterials at Any Angle of Incidence

The quantum optics of metamaterials starts with the question of whether the same effective-medium theories apply as in classical optics. In general, the answer is negative. For active plasmonics but also for some passive metamaterials, we show that an additional effective-medium parameter is indispensable besides the effective index, namely, the effective noise-photon distribution. Only with the extra parameter can one predict how well the quantumness of states of light is preserved in the metamaterial. The fact that the effective index alone is not always sufficient and that one additional effective parameter suffices in the quantum optics of metamaterials is both of fundamental and practical interest. Here, from a Lagrangian description of the quantum electrodynamics of media with both linear gain and loss, we compute the effective noise-photon distribution for quantum light propagation in arbitrary directions in layered metamaterials, thereby detailing and generalizing our previous work. The effective index with its direction and polarization dependence is the same as in classical effective-medium theories. As our main result, we derive both for passive and for active media how the value of the effective noise-photon distribution too depends on the polarization and propagation directions of the light. Interestingly, for s-polarized light incident on passive metamaterials, the noise-photon distribution reduces to a thermal distribution, but for p-polarized light it does not. We illustrate the robustness of our quantum optical effective-medium theory by accurate predictions both for power spectra and for balanced homodyne detection of output quantum states of the metamaterial.

Omnidirectional defect mode in one-dimensional photonic crystal with a (chiral) hyperbolic metamaterial defect.

The wavelength of defect mode in all-dielectric photonic crystals (PCs) with a dielectric defect are blue-shifted as incident angle increases for both transverse electric and transverse magnetic (TM) polarized waves. The blue-shifted property of defect mode limits the design of some optical devices including omnidirectional optical filters and wide-angle polarization selectors. Here we introduce a hyperbolic metamaterial (HMM) layer as a defect into dielectric one-dimensional photonic crystals (1DPCs) to obtain an omnidirectional defect mode for TM polarized waves at near-infrared regimes. Since only one HMM layer is introduced, omnidirectional defect mode with transmittance as high as 71% can be realized. Because of the unusual angle-dependence of propagating phase in the HMM defect, the total phase for satisfying the resonance condition of defect mode can be unchanged in a wide-angle range at a fixed wavelength, which leads to the omnidirectional defect mode. Moreover, the manipulation of propagating phase can be generalized to the case of circularly polarized waves, and we obtain an omnidirectional defect mode for left-handed circularly polarized waves in 1DPCs with a chiral hyperbolic metamaterial defect. Nevertheless, the defect mode for right-handed circularly polarized waves is still blue-shifted. Such spin-selective omnidirectional defect mode can be utilized to greatly enhance circular dichroism in a wide-angle range up to 64.1°. Our structure facilitates the design of omnidirectional optical filters with a high transmittance and circular polarization selectors working in a wide-angle range.

Reflection and transmission of nanoresonators including bi-isotropic and metamaterial layers: opportunities to control and amplify chiral and nonreciprocal effects for nanophotonics applications

Electromagnetic waves reflected from and transmitted through the multilayer nanoresonators including the main layer made of a bi-isotropic material or metamaterial sandwiched between dielectric, epsilon-near-zero or metallic spacer layers have been analytically modeled. The numerical and graphical analysis, based on the exact solution of the electromagnetic boundary problem, confirms opportunities to use such nanoresonators as utracompact polarization converters. The proposed systems are characterized by wide ranges of parameters and significantly reduced (subwavelength) thicknesses. The spacer layers can provide modification, control, and amplification of chiral and nonreciprocal effects for the reflected and transmitted radiation. The concept can be realized for various geometries of dielectric, epsilon-near-zero, metallic, bi-isotropic, metamaterial layers and used to develop new ultrathin, large area, and relatively easy-to-manufacture polarization and other devices for nanophotonics.