Multilayer Metamaterials Research Articles

Tunable multistate terahertz switch based on multilayered graphene metamaterial

We proposed plasmonic effect-based narrow band tunable terahertz switches consisting of multilayered graphene metamaterial. Though several terahertz optical switches based on metamaterials were previously reported, these switches had complicated fabrication processes, limited tunability, and low modulation depths. We designed and simulated ingenious four- and eight-state terahertz optical switch designs that can be functional for multimode communication or imaging using the finite-difference time-domain simulation technique. The plasmonic bright modes and transparency regions of these structures were adjusted by varying the chemical potential of patterned graphene layers via applying voltage in different layers. The structures exhibited high modulation depth and modulation degree of frequency, low insertion loss, high spectral contrast ratio, narrow bandwidth, and high polarization sensitivity. Moreover, our proposed simple fabrication process will make these structures more feasible compared to previously reported terahertz switches. The calculated modulation depths were 98.81% and 98.71%, and the maximum modulation degree of frequencies were $$\sim$$ 61% and $$\sim$$ 29.1% for four- and eight-state terahertz switches, respectively. The maximum transmittance in transparency regions between bright modes and the spectral contrast ratio were enumerated to be 95.9% and $$\sim$$ 96%, respectively. The maximum insertion losses were quite low with values of 0.22 dB and 0.33 dB for four- and eight-state terahertz switches, respectively. Our findings will be beneficial in the development of ultra-thin graphene-based multistate photonic devices for digital switching and sensing in the terahertz regime.

Bioinspired multiple-degrees-of-freedom responsive metasurface by high-entropy-alloy ribbons with hierarchical nanostructures for electromagnetic wave absorption

The compound eyes of the dragonfly, Pantala flavescens Fabricius, are covered by micro-scaled ocelli capable of sensing polarized light, an attractive property for radar stealth and counterreconnaissance. In this work, we fabricated biomimetic electromagnetic wave absorption materials (EAMs) by analyzing the covert information identifications of biological systems and focusing on the design of metastructures and microstructures. Several bionic metasurfaces with anisotropic double-V meta atoms made up of (FeCoNiSi8.9Al8.9)C0.2 high-entropy-alloy (HEA) ribbons for multiple-degrees-of-freedom recognition and broadband absorption are presented. The covert phase, amplitude, and angular momentum of electromagnetic waves were controlled and recognized as information by manipulating the rotation angle θ of meta atoms. A vortex wave with a topological charge of 1 was generated to recognize linearly polarization and left- and right-handed circular polarization. In addition, the polarization conversion enhanced absorption. The hierarchical nanostructures of HEA ribbons give rise to suitable electromagnetic loss and a superior impedance match. Finally, inspired by the structure of compound eyes, the designed multilayer metamaterials realized effective absorption (reflection loss (RL) ≤ − 10 dB) within the 4.5–18 GHz regime under 2.8 mm thickness. These materials provide evidence for a new way for integrated EAMs and metamaterials.

Effect of geometry, anisotropy and composition on the third-order optical nonlinearities of multilayer hyperbolic metamaterials -INVITED

Quantum technologies require advanced optical metamaterials whose properties can be tailored and controlled as desired. Hyperbolic metamaterials have great potential for applications in nonlinear nanophoton-ics, such as all-optical switching, optical limiting, mode-locking and optical sensing. In this work, we show how to obtain strong third-order optical nonlinearities in hyperbolic multilayers exploiting the effect of bulk plas-mon polaritons. We demonstrate the tunability of these properties with angle and polarization, and we propose a model to predict them. We evidence the enhancement of the nonlinear response in low-loss metamaterials.

Figure of merit for design of ε-near-zero metamaterials with enhanced Kerrtype nonlinearities

Metamaterials are artificial media designed to display properies going beyond those of ordinary materials. Particularly interesting are ε-near-zero (ENZ) media with real part of the permittivity going to zero in a certain spectral range. Examples of ENZ metamaterials are metal dielectric multilayers, which allow to tune the position of the ENZ wavelength depending on their composition and which have been found to have enhanced Kerr-type nonlinearities, i.e. nonlinear absorption and nonlinear refraction. In this work we define a figure of merit for the design of multilayer metamaterials with strong Kerr-type nonlinearities and compare our predictions with both simulations and experimental results.

Neural Network Design of Multilayer Metamaterial for Temporal Differentiation

AbstractControlling wave−matter interactions with metamaterials (MTMs) for the calculation of mathematical operations has become an important paradigm for analogue computing given their ability to dramatically increase computational processing speeds. Here, motivated by the importance of performing mathematical operations on temporal signals, multilayer MTMs with the ability to calculate the derivative of temporally modulated signals are proposed, designed, and studied. To do this, a neural network (NN) based algorithm is used to design the multilayer structures (alternating layers of indium tin oxide (ITO) and titanium dioxide (TiO2)) that can calculate the first temporal derivative of the envelope of an impinging electromagnetic signal modulated at telecom wavelengths (1550 nm). Different designs are presented using multiple incident temporal signals including a modulated Gaussian as well as modulated arbitrary functions, demonstrating an excellent agreement between the predicted results (NN results) and the theoretical (ideal) values. It is shown how the proposed NN‐based algorithm can complete its search of the design space for the layer thicknesses of the multilayer MTM after just a few seconds, with a low mean square error in the order of (or below) 10−4 when comparing the predicted results with the theoretical spectrum of the ideal temporal derivative.

Hyperbolic metamaterial structures based on graphene for THz super-resolution imaging applications

The diffraction limit of light due to the loss of evanescent waves that carry high spatial frequency information in the far field restricts the practical applications of terahertz imaging technology. In order to break the diffraction limit, we investigate the super-resolution capability of different types of multilayered graphene-dielectric hyperbolic metamaterials. A super-resolution of λ/10 is achieved for both the cylindrical and planar structures. A prominent advantage of graphene-dielectric hyperbolic structures is the dynamic tunability of the dispersion and super-resolution performance by adjusting the chemical potential of graphene through conveniently changing the gate voltage without modifying the geometry of the hyperbolic structures. Furthermore, we have investigated the influence of bilayer thickness variations on the super-resolution performance. Finally, we apply the planar hyperbolic structures for the super-resolution imaging and a roughly five-fold lateral resolution enhancement is realized in our approach. Due to many prominent advantages including super-resolution over broad spectral range, dynamic tunability, good stability and robustness, we believe this work could contribute to the improvement of the resolutions of terahertz imaging systems and the development of hyperbolic metamaterial modulation devices in the terahertz band.

Deep‐Subwavelength Optical Spin Textures in Volume Plasmon Polaritons with Hyperbolic Metamaterials

AbstractHyperbolic metamaterials can support extremely high‐k wavevectors, also known as volume plasmon polaritons, with highly directional propagation and light confinement to deep‐subwavelength scales. The number of high‐k modes has an inverse relationship with the overall thickness of hyperbolic metamaterials. Here, the optical spin textures from high‐k mode polaritons on the surface of silica–silver multilayer hyperbolic metamaterials are studied. The results demonstrate that with an increase in the overall thickness, the spin texture changes from a twisted structure to a Néel‐type photonic skyrmion, due to the decrease in the number of high‐k modes. Moreover, the size of a single photonic skyrmion is less than 1/2 of the light wavelength, and the full width at half maximum of the spin angular momentum is less than 1/9 of the light wavelength. This work is expected to facilitate new applications of hyperbolic metamaterials, such as spin‐dependent excitation and detection devices at the deep‐subwavelength level.

Multicomponent induced localized coupling in Penrose tiling for electromagnetic wave absorption and multiband compatibility

• Design quasiperiodic absorbers with long-range order but no periodicity. • Explored the relationship between electromagnetic parameters and frequency by structural design and component selection in depth. • The effective absorption bandwidth of Penrose absorber can realize 9.32 GHz in 2 mm thickness. • The multilayer metamaterials perfectly unify radar-infrared compatible capability. In the electronic information and intelligent era, microwave absorption materials have been focused on the issue of electromagnetic (EM) pollution, but high-performance absorbers with thin thickness are highly desirable. The positive action between structural design and component selection can be regarded as a function to optimize the microwave loss capacity, which contributes to understanding the response mechanisms from the micro and macro. Therefore, we designed the absorber with quasiperiodic structures of Penrose tiling that has finely engineered the location of maximum absorption peak, the spherical carbonyl iron in thin rhombus, and flakey carbonyl iron in fat rhombus, the effective absorption bandwidth (Reflection Loss ≤ –10 dB) was realized from 6.46 GHz to 15.78 GHz in the 2 mm thickness. The unique arrangement of Penrose tiling can respond alternatingly to EM waves at large scales, and multicomponent coupling is distinctly in the neighboring unit cells. In addition, spraying aluminum pigment as the upper layer, the infrared emissivity is less than 0.35 to meet the complex application environment. This work opens up novel ideas on quasiperiodic structure combined multicomponent and injects infinite vitality to provide prospects for broadband responsive and high-efficiency EM absorbers.

Research on the structural design and pentamodal property of three-dimensional multilayer cylindrical pentamode metamaterials for tuning acoustic waves

Pentamode metamaterial (PM) is an artificial solid form metamaterial with fluid characteristics. In this paper, a three-dimensional (3D) PMs based on multilayer cylindrical elements are proposed for increasing tunable structure parameters, obtaining great pentamodal property, reducing band gap frequency and decreasing connection overlap areas of elements. Compared with the PMs with double-cone elements, under the same parameters, the lower edge frequency of the single-mode band gaps can be reduced by 33.2%, the maximum value of figure of merit can be increased by 84.8% and the phononic band gaps can be reduced by 73.9%.

Feasible Extraction Method for Electromagnetic Properties of Multilayer Metamaterials With Short-Circuit Termination

An extraction technique is proposed for electromagnetic characterization of metal-backed multilayer metamaterial (MM) structures demonstrating reflection-asymmetric property. It uses recursive scattering parameters for direct and reversed configurations of a multilayer structure. The algorithm was validated by comparing the extracted electromagnetic properties of multilayer structures composed of different MM unit cells with those determined by one-layer-only S-parameter methods. Two-layer and three-layer multilayer structures composed of MM slabs with C-shaped and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> -shaped rings and an FR4 material were fabricated and measured for experimental validation. A sensitivity analysis was also conducted to quantitatively evaluate the performance of our method against a small air gap between the multilayer structures and the short-circuit termination and between adjacent MM slabs within these structures. Strong agreement was observed between the resulted obtained using our method and measurements.

Gain-Assisted Giant Third-Order Nonlinearity of Epsilon-Near-Zero Multilayered Metamaterials.

We investigate the third-order nonlinear optical properties of epsilon-near-zero (ENZ) Au/dye-doped fused silica multilayered metamaterials in the visible spectral range for TM incident by using nonlocal effective medium theory at different incidence angles. The nonlocal response affects the permittivity of anisotropic metamaterials when the thickness of the layer cannot be much smaller than the incident wavelength. By doping pump dye gain material within the dielectric layer to compensate for the metal loss, the imaginary part of the effective permittivity is reduced to 10−4, and the optical nonlinear refractive index and nonlinear absorption coefficient are enhanced. The real and imaginary parts of the permittivity are simultaneously minimized when the central emission wavelength of the gain material is close to the ENZ wavelength, and the nonlinear refraction coefficient reaches the order of 10−5 cm2/W, which is five orders of magnitude larger than that of the nonlinear response of the metamaterial without the gain medium. Our results demonstrate that a smaller imaginary part of the permittivity can be obtained by doping gain materials within the dielectric layer; it offers the promise of designing metamaterials with large nonlinearity at arbitrary wavelengths.

The Broad Band Optical Absorber Designed By Multilayered Hyperbolic Metamaterial

Bu çalışmada, özellikle optik bölgede geniş band soğurma gösteren çok tabakalı bir hiperbolik metamalzeme tasarlanmıştır. Tasarlanan yapıda üç farklı metal (Ag, Au ve Al) ve yarıiletken bir malzeme (InGaAs) kullanılmıştır. Hesaplamalarda Transfer Matris Metodundan (TMM) yararlanılmıştır. Bu yöntem kullanılarak tasarlanan çok tabakalı yapıların optik soğurma ve yansıma spektrumları gelme açısına bağlı olarak incelenmiştir. Metal-dielektrik çok tabakalı yapıların hiperbolik dispersiyon gösterdiği bölgeler belirlenmiş, ayrıca gelme açısına bağlı kontur grafikleri elde edilmiştir. Yapılan hesaplamalar sonucunda, metal olarak gümüşün kullanıldığı heteroyapının en iyi soğurma spektrumu verdiği gözlenmiştir.

Bulk Plasmon Polariton Modes in Hyperbolic Metamaterials for Giant Enhancement of the Transverse Magneto-Optical Kerr Effect.

We demonstrate a concept for the giant enhancement of the transverse magneto-optical Kerr effect (TMOKE) using bulk plasmon polariton (BPP) modes in non-magnetic multilayer hyperbolic metamaterials (HMMs). Since the BPP modes are excited through the attenuated total reflection (ATR) mechanism, using a Si-based prism-coupler, we considered a single dielectric magneto-optical (MO) spacer between the prism and the HMM. The working wavelength was estimated, using the effective medium approach for a semi-infinite dielectric-plasmonic multilayer, considering the region where the system exhibits type II HMM dispersion relations. Analytical results, by means of the scattering matrix method (SMM), were used to explain the physical principle behind our concept. Numerical results for giant TMOKE values (close to their maximum theoretical values, ) were obtained using the finite element method (FEM), applying the commercial software COMSOL Multiphysics. Our proposal comprises a simple and experimentally feasible structure that enables the study of MO phenomena in HMMs, which may find application in future nanostructured magnetoplasmonic metamaterials for active nanophotonic devices.

Highly Q-factor refractive index sensor based on graphene stack

The perfect absorber with high figure of merit (FOM) and sensitivity for mid-infrared application is developed in this study. The structure contains a nanoaperture as a resonator and multi-layer hyperbolic metamaterial of graphene-SiN is place under the nanoaperture to increasing the absorption. The results show how the chemical potential of graphene can improve the absorbance. Finally, a coat of SiO2 is pinpointed over the nanoaperture for enhance the absorption and protecting the surface. The proposed aperture is designed symmetrically based on crossed shape to reduce the polarization effects on sensing. The Q-factor has increased sharply to 3000 for the final device by utilizing the hyperbolic material structure. The left-hand characteristic of the hyperbolic metamaterial provides a condition for concentrating the surface Plasmon’s at the interface of the gold layer with the substrate, leading to the reflection reduction to − 46 dB. This absorber is considered as an optical sensor for various materials under test (MUT) in the optical spectrum and it is simulated by FIT method as a time-domain technique. This sensor has a sensitivity of 400 nm/RIU and the FOM of 89000 RIU−1.

Deployment kinematics of axisymmetric Miura origami: Unit cells, tessellations, and stacked metamaterials

Origami is emerging as a promising paradigm for deployable structures. The theoretical analysis on the relationship between geometry of the crease patterns and the induced deployment mechanisms is the key to the rational design of origami-inspired deployable structures. In this paper, we systematically investigate the deployment kinematics of axisymmetric Miura origami from unit cells to single-layer tessellations and multi-layer stacked metamaterials. We show that the axisymmetric Miura cells can be classified into two categories according to the monotonicity of the angular motion, and the axisymmetric Miura origami tessellations can be classified into seven categories based on the developability, flat-deployability, and the ability to form closed-ring shapes. We also derive the conditions for the deployability of the multi-layer metamaterials constructed by stacking axisymmetric Miura origami tessellations. Both the singly and doubly curved cases are studied for the tessellations and metamaterials. Additionally, based on the kinematic formulations, we develop an easy-to-implement optimization framework for the design of doubly curved axisymmetric Miura origami tessellations that approximate surfaces of revolution. The optimized shape-morphing tessellations can also be used to assemble multi-layer stacked metamaterials. Taken together, these results provide a comprehensive guidance to design axisymmetric deployable structures based on origami principles.

Erratum to: Controlling the plasmon resonance via epsilon-near-zero multilayer metamaterials

Erratum to: Controlling the plasmon resonance via epsilon-near-zero multilayer metamaterials

Design and analysis of terahertz filters based on multilayer metamaterials.

We numerically and experimentally demonstrate a series of multilayer metamaterial filters in the terahertz region. The designed structure consists of multiple metal-polyimide composite layers and cyclic olefin copolymer layers. The transmission spectra of the filters are characterized by terahertz time-domain spectroscopy, and the measured results agree well with simulations. In addition, the mechanism of the multilayer structure is theoretically studied by a thin film multibeam interference model. The proposed filters exhibit high efficiency at passband and can be broadly utilized as compact devices in practical applications at terahertz frequencies.

Switchable Multifunctional Terahertz Metamaterials Based on the Phase-Transition Properties of Vanadium Dioxide.

Currently, terahertz metamaterials are studied in many fields, but it is a major challenge for a metamaterial structure to perform multiple functions. This paper proposes and studies a switchable multifunctional multilayer terahertz metamaterial. Using the phase-transition properties of vanadium dioxide (VO2), metamaterials can be controlled to switch transmission and reflection. Transmissive metamaterials can produce an electromagnetically induced transparency-like (EIT-like) effect that can be turned on or off according to different polarization angles. The reflective metamaterial is divided into I-side and II-side by the middle continuous VO2 layer. The I-side metamaterials can realize linear-to-circular polarization conversion from 0.444 to 0.751 THz when the incident angle of the y-polarized wave is less than 30°. The II-side metamaterials can realize linear-to-linear polarization conversion from 0.668 to 0.942 THz when the incident angle of the y-polarized wave is less than 25°. Various functions can be switched freely by changing the conductivity of VO2 and the incident surface. This enables metamaterials to be used as highly sensitive sensors, optical switches, and polarization converters, which provides a new strategy for the design of composite functional metamaterials.

Design and Analysis of Multi-Layer and Cuboid Coding Metamaterials for Radar Cross-Section Reduction

This research aimed to develop coding metamaterials to reduce the Radar Cross-Section (RCS) values in C- and Ku-band applications. Metamaterials on the macroscopic scale are commonly defined by effective medium parameters and are categorized as analogue. Therefore, coding metamaterials with various multi-layer and cuboid designs were proposed and investigated. A high-frequency electromagnetic simulator known as computer simulation technology was utilised throughout a simulation process. A one-bit coding metamaterial concept was adopted throughout this research that possesses ‘0’ and ‘1’ elements with 0 and π phase responses. Analytical simulation analyses were performed by utilising well-known Computer Simulation Technology (CST) software. Moreover, a validation was executed via a comparison of the phase-response properties of both elements with the analytical data from the High-Frequency Structure Simulator (HFSS) software. As a result, promising outcomes wherein several one-bit coding designs for multi-layer or coding metamaterials manifested unique results, which almost reached 0 dBm2 RCS reduction values. Meanwhile, coding metamaterial designs with larger lattices exhibited optimised results and can be utilised for larger-scale applications. Moreover, the coding metamaterials were validated by performing several framework and optimal characteristic analyses in C- and Ku-band applications. Due to the ability of coding metamaterials to manipulate electromagnetic waves to obtain different functionalities, it has a high potential to be applied to a wide range of applications. Overall, the very interesting coding metamaterials with many different sizes and shapes help to achieve a unique RCS-reduction performance.

Plasmon mode manipulation based on multi-layer hyperbolic metamaterials.

Metamaterial with hyperbolic dispersion properties can effectively manipulate plasmonic resonances. Here, we designed a hyperbolic metamaterial (HMM) substrate with a near-zero dielectric constant in the near-infrared region to manipulate the plasmon resonance of the nano-antenna (NA). For NA arrays, tuning the equivalent permittivity of HMM substrate by modifying the thickness of Au/diamond, the wavelength range of plasmon resonance can be manipulated. When the size of the NA changes within a certain range, the spectral position of the plasmon resonance will be fixed in a narrow band close to the epsilon-near-zero (ENZ) wavelength and produce a phenomenon similar to "pinning effect." In addition, since the volume plasmon polaritons (VPP) mode is excited, it will couple with the localized surface plasmon (LSP) mode to generate a spectrum splitting. Therefore, the plasmon resonance is significantly affected and can be precisely controlled by designing the HMM substrate.