Transverse Electric Waves Research Articles

Multiple plasmonic resonance excitations on graphene metamaterials for ultrasensitive terahertz sensing

A three-dimensional graphene metamaterial structure consisting of dielectric pillar arrays covered by graphene monolayer with metal layer underneath is proposed and investigated, which can realize the efficient excitations of multiple plasmonic resonance modes under incident terahertz (THz) wave. The multiple plasmonic resonance modes are highly sensitive to the change of analyte refractive index and thickness, and the frequency sensitivity of each resonance mode can reach up to 1.402, 1.687 and 1.643 THz per refractive index unit, respectively. By controlling the Fermi level of graphene, the resonance frequency can be tuned dynamically. Moreover, the proposed structure has three absorption peaks with absorptivity more than 95%, it is polarization-insensitive and can perform very well in a wide incident angles for transverse electric and transverse magnetic waves. This proposed structure can be utilized for active THz plasmonic devices such as multiple channel sensors and absorbers.

Dispersion Properties of an Elliptical Patch with Cross-Shaped Aperture for Synchronized Propagation of Transverse Magnetic and Electric Surface Waves

This paper presents a novel pixel geometry for the implementation of metasurfaces requiring synchronized phase propagation of transverse magnetic (TM) and transverse electric (TE) modes. The pixel is composed by an elliptical metallic patch with an asymmetric cross-shaped aperture in the center, printed on a grounded slab. A practical implementation of a metasurface was carried out employing such a pixel geometry. Simulation results show similar frequency dispersion properties for both modes within the working frequency band, in agreement with the theoretical basis.

Wide Bandwidth and Enhanced Gain of a Low-Profile Dipole Antenna Achieved by Integrated Suspended Metasurface

A low-profile metasurface-based dipole antenna is proposed, analyzed, and implemented for the wideband operation with improved gain. The metasurface is suspended by separating it from the ground plane with an air gap and positioning it right beneath a horizontally oriented dipole. The wide operating bandwidth is attributed to the simultaneous excitation of the transverse electric surface wave resonance of the suspended metasurface (SMS) and the adjacent metasurface-based dipole resonance. The small propagation constant of transverse magnetic surface wave in the operating band enlarges the SMS aperture along the dipole direction for higher gain compared to a conventional low-profile antenna. The proposed antenna design with an overall thickness of $0.07\lambda $ ( $\lambda $ is the wavelength in free space at the center operating frequency) shows the realized boresight gain of 8.5–11.5 dBi over $\vert \text{S}_{11}\vert \le -10$ dB impedance bandwidth of 33.6% (or 4.15–5.85 GHz).

Experimental Validation of a Ku-Band Dual-Circularly Polarized Metasurface Antenna

The experimental validation of a Ku-band dual-circularly polarized (CP) broadside-beam metasurface (MTS) antenna is presented. A radially modulated anisotropic single-layer MTS has been synthesised employing subwavelength elliptical slotted metallic patches printed on top of a thin Arlon grounded substrate. In the structure, two decoupled phase-matched transverse magnetic and transverse electric surface waves (SWs) are excited, which interact with the modulated surface leading to a CP broadside radiation. Two different orthomode transducers have been designed to excite the SWs with orthogonal polarization and equal amplitude. The first feeding system is composed of a metallic stepped septum inside an air-filled square waveguide. A conical section is included to match the output port of the square waveguide with the terminal, dielectric filled circular waveguide. The second feed is much more compact and efficient, and it is composed of a circular waveguide completely filled by a dielectric. Depending on the input port excited on the feeds, two TE11 modes are excited with ±90° phase shift, which determine the right-hand or left-hand sense of the broadside beam generated by the MTS. Manufacturing details of the MTS and excitations are given, and the measurements are compared with the simulation results. Finally, conclusions are drawn.

Dual-band transmission polarization converter based on planar-dipole pair frequency selective surface

A novel linear polarization converter operating in C- and X-bands with high polarization conversion ratio is described and demonstrated based on frequency selective surface. The building element is a planar-dipole pair, which is orthogonally printed on a double-layer substrate and vertically connected by a pair of through-via holes functioning as a quasi-two-wire transmission line coupler. A perforated metal shielding layer is sandwiched between the double-layer structure to only support a transverse electric and magnetic (TEM) mode coupling between the top and bottom dipolar components. The front dipole responds to the incident transverse electric (TE) wave, and sends the induced current into the two-wire transmission line to feed the bottom dipole. The bottom dipole is orthogonal or oriented at an arbitrary angle with respect to the top one, and a resultant outgoing transverse magnetic (TM) wave or arbitrary orientation polarized wave can be achieved. In addition, a bidirectional orthogonal polarization converter is realized by using double orthogonally arranged planar-dipole pairs, which are also printed on the same double-layer substrate.

Periodic multilayer magnetized cold plasma containing a doped semiconductor

The present work is to numerically investigate the properties of the defect mode in a one-dimensional photonic crystal made of magnetized cold plasma, doped by semiconductor. The defect mode of such kind of multilayer structure is analyzed by applying the character matrix method to each individual layer. Numerical results illustrate that the defect mode frequency can be tuned by varying the external magnetic field, the electron density, and the thickness of the defect layer. Moreover, the behavior of the defect mode was found to be quite interesting when study the oblique incidence. It was found that for both right- and left-hand polarized transversal magnetic waves, the defect mode of the proposed defective structure disappears when the angle of incidence is larger than a particular oblique incidence. For the left-hand polarized transversal electric wave, however, an additional defect mode was noticed. The results lead to some new information concerning the designing of new types of tunable narrowband microwave filters.

Dual circularly polarized broadside beam antenna based on metasurfaces

Design details of a Ku band metasurface (MTS) antenna with dual circularly polarized (CP) broadside radiation is shown in this work. By means of the surface impedance tensor modulation, synchronized propagation of two transversal magnetic (TM) and transverse electric (TE) surface waves (SWs) is ensured in the structure, which contribute to the radiation in broadside direction by the generation of a CP leaky wave. The structure is implemented by elliptical subwavelength metallic elements with a cross-shaped aperture in the center, printed on top of a thin substrate with high permittivity (AD1000 with a thickness of λ0/17). For the experimental validation, the MTS prototype has been excited employing an orthomode transducer composed by a metallic stepped septum inside an air-filled waveguide. Two orthogonal TE11 modes excited with ±90° phase shift in the feed couple with the TM and TE SWs supported by the MTS and generate RHCP or LHCP broadside beam. Experimental results are compared with the simulation predictions. Finally, conclusions are drawn.

Analysis of Plasmonic Structure using Finite Element Method

Plasmonic structure was investigated by modelling the different shape of v-groove shape and curve shape in three dimension (3D) using Finite Element Method (FEM). We simulate and compare the shape with electric and magnetic wave propagation in term of total electric energy and total magnetic energy using gold as a metal material and glass as a dielectric material. The result of the reflection and transmission of transverse electric (TE) wave and transverse magnetic (TM) wave with the angle of incidence are shown depending on the shape of plasmonic structure by using analytic solution based on Fresnel equation.

Theoretical design and analysis of wideband active hard electromagnetic surfaces using non-Foster circuit loaded anisotropic metasurfaces

The electromagnetic (EM) hard surface which can both support transverse electric and transverse magnetic surface wave modes has the important ability to reduce the EM blockage of metallic obstacles. We propose a method to design an electrically thin hard surface with wide bandwidth by loading with non-Foster elements. The wideband hard surface composed of an anisotropic impedance coating can be considered as a kind of active metasurface. We develop a method to determine the values of the loading non-Foster circuit which can minimize the dispersion of the unit cells. For this method, we derive accurate values for the loading non-Foster elements through theoretical analysis. We also determine the fundamental limitations on the bandwidth due to stability requirements. To verify our theoretical design, we simulate the transmission performance between the two ports on opposite sides of a metallic rhombus-shaped obstacle coated with the non-Foster based metasurface. The simulated results show that the blockage has been largely reduced over a broad bandwidth from 0.2 GHz to 1.5 GHz. Finally, we provide a discussion on how the resistive part of the non-Foster circuit can affect the performance of the wideband hard surface coating.

Anisotropic polarization beam splitter based on metal slit array

Polarizing beam splitter (PBS) can separate the propagating directions of two incident orthogonally polarized light beams. However, conventional PBS and multi-layered metamaterial structures are complicated and neither of them can meet the requirements for broadband characteristics due to their resonant characters. In this paper, an anisotropic beam splitter based on metal slit array of the metal-dielectric structure is proposed in order to simplify the structure and improve the beam splitting efficiency. Because of the transverse momentum generated by the inhomogeneous interface, the transverse magnetic (TM) wave is negatively reflected from the surface of the gold film after it has entered into the slit with the waveguide mode of the plasma. When the free electrons on the metal surface oscillate, the transverse electric (TE) wave parallel to the grating direction can cause electrons to oscillate along the grating direction, so that the TE light cannot enter into the slit, resulting in specular reflection. The finite element method is used to study the effects of TM and TE polarized light such as negative reflection (NR) and specular reflection (SR). The results show that when the incident angle of the polarized light is set to be in a range from 20 to 70, the incident TM light has a strong NR of about 0.9, but the TE light is weakly reflected and decreases sharply with the increase of the wavelength. The ideal NR points of the beam splitter and the perfect symmetrical response of the reflection surface are calculated, and the ideal NR point satisfies P=/(2sin 0). When the incident light angle changes, the variations of the wavelength of the negative and zero order reflection peak are different from those of TM and TE wave, which is more conducive to the tuning of the interaction between light and grating structure. The NR and SR spectral reflectance of different polarized light beams are calculated by rigorous coupled-wave analysis, and the extinction ratios in the two cases are both 106. In addition, those designs of plasmonic splitters will pave the way for the practical applications of plasmonic devices in data storages and optical holography.

Polarization-controlled dual-band broadband infrared absorber

As an important branch of metamaterial-based devices, metamaterial absorber (MA) has aroused great interest and made great progress in the past several years. By manipulating the magnetic resonance and the electric resonance simultaneously, the effective impedance of MA will match the free space impedance, thus resulting in a perfect absorption of incident waves. Due to the advantages of thin thickness, flexible design and tunable property, MA has been extensively studied at various frequencies, e. g. microwave frequency, THz, infrared frequency, and optical frequency. Infrared MA, having important applications in infrared stealth, infrared detection, radiative cooling, and sensors, receives more and more attention, especially for those absorbers based on easy-fabricated one-dimensional grating structure. However, such a grating-based absorber is usually workable in narrow band and effective only for transverse magnetic (TM) wave.In this paper, a dual-band broadband absorber is proposed based on the easy-fabricated grating structure. The basic unit of the proposed absorber consists of eight gradient subunits, each of which is composed of vertically cascaded two pairs of metal-dielectric bilayers. The as-designed absorber has perfect absorption for both TM and transverse electric (TE) waves. More importantly, the absorption band is different for different polarized wave, which provides more choices and greater flexibility for application. Full-wave simulation shows that the absorption of TM wave is above 90% from 1.68 μm to 2 μm, while the absorption of TE wave is very small (no more than 6%). The absorption of TE wave is above 90% from 3.8 to 3.9 μm, while the absorption of TM wave is very small (no more than 5%). In order to reveal the working principle of the proposed absorber, the electric-field distributions of the whole structure are calculated at different frequency, which demonstrates that the broadband absorption is achieved by exciting multiple resonant coupling. Furthermore, we investigate the performance of the proposed absorber in oblique incidence, and find that the designed absorber can exhibit a good absorption within a broad incident angle ranging from 0 to 60 degrees. It is worth noting that there is an absorption fracture band in the absorption spectrum of TM waves, which is because no resonance occurs in all subunits, resulting in almost no absorption.In conclusion, we have proposed a dual-band broadband absorber that demonstrates independent absorption of the TM waves and the waves in different bands, which has potential applications in thermal detectors and thermal emitters. The proposed scheme can be extended to microwave, THz, and even visible light band.

Perfect broadband invisibility in isotropic media with gain and loss.

We offer a simple route to perfect omnidirectional invisibility in a spectral band of desired width. Our approach is based on the observation that in two dimensions a complex potential v(x,y) is invisible for incident plane waves with a wavenumber not exceeding a pre-assigned value α, provided that its Fourier transform with respect to y, which we denote by v˜(x,Ky), vanishes for Ky≤2α. We can fulfill this condition for potentials modeling the permittivity profile of an optical slab. Such a slab is perfectly invisible for any transverse electric wave whose wavenumber is in the range [0,α]. Our results also apply to transverse magnetic waves propagating in a medium with a relative permittivity ϵ^(x,y) that is a smooth bounded function with a positive real part.

Transverse electric surface waves in a plasma medium bounded by magnetic materials

Abstract The transverse electric surface waves have been investigated with a plasma medium sandwiched between two ferrite films. The characteristic equations for the field components are derived and a dispersion relation is analytically obtained by using boundary conditions for the tangential field components. Numerical analysis shows the plots of effective wave index with surface wave frequency for different thicknesses and number densities of the plasma medium, and also for the different values of the dielectric constant of the ferrite films.

Confined transverse electric phonon polaritons in hexagonal boron nitrides

We predict the existence of confined transverse electric (TE) phonon polaritons in an ultrathin hexagonal boron nitride (hBN) slab below hBN’s second transverse optical frequency. The skin depth of TE phonon polaritons can be decreased to subwavelength scale by increasing the thickness of hBN to several nanometers. Due to the strong spatial confinement, these TE phonon polaritons, different from TE graphene plasmons, can stably exist even when the permittivities of the superstrate and substrate are largely different. These revealed advantages of TE phonon polaritons might lead to potential applications of hBN in the manipulation of TE waves, such as the design of novel waveguides, polarizers, and the exploration of negative refraction between TE polaritons.

Design of Broadband Metamaterial Absorbers for Permittivity Sensitivity and Solar Cell Application**Supported by the National Natural Science Foundation of China under Grant No 61275174, and the Research Fund for the Doctoral Program of Higher Education of China under Grant No 20100162110068.

A broadband and ultra-thin absorber for solar cell application is designed. The absorber consists of three layers, and the difference is that the four split ring resonators made of metal gold are encrusted in the gallium arsenide (GaAs) plane in the top layer. The simulated results show that a perfect absorption in the region from 481.2 to 684.0 THz can be obtained for either transverse electric or magnetic polarization wave due to the coupling effect between the material of GaAs and gold. The metamaterial is ultra-thin, having the total thickness of 56 nm, which is less than one-tenth resonance wavelength, and the absorption coefficients at the three resonance wavelengths are above 90%. Moreover, the effective medium theory, electric field and surface current distributions are adopted to explain the physical mechanism of the absorption, and the permittivity sensing applications are also discussed. As a result, the proposed structure can be used in many areas, such as solar cell, sensors, and integrated photodetectors.

Nonlocal effect on the transmission of a transverse electric electromagnetic wave through periodic dielectric-metal multilayers

The problem of electromagnetic response of a periodic dielectric-metal structure to transverse electric electromagnetic excitation is solved analytically on the basis of the Boltzmann kinetic equation formalism. We analyze the dispersion relation, transmission coefficient, and absorption for different angles of incidence. We show that, due to nonlocal dependence of the electron current density on the electric field in metal layers, the THz and near-infrared photonic properties of dielectric-metal structures are strikingly different from those obtained with the use of the simplified description based on the Drude–Lorentz model. In the limit of weak spatial dispersion, the developed theory reproduces the known results for transverse electric electromagnetic waves scattered by layered structures consisting of spatially local layers.

Spectral theory for Maxwell’s equations at the interface of a metamaterial. Part I: Generalized Fourier transform

ABSTRACTWe explore the spectral properties of the time-dependent Maxwell’s equations for a plane interface between a metamaterial represented by the Drude model and the vacuum, which fill, respectively, complementary half-spaces. We construct explicitly a generalized Fourier transform which diagonalizes the Hamiltonian that describes the propagation of transverse electric waves. This transform appears as an operator of decomposition on a family of generalized eigenfunctions of the problem. It will be used in a forthcoming paper to prove both limiting absorption and limiting amplitude principles.

Study on the properties of the two-dimensional curved surface metamaterial

Metamaterials become a breakthrough technology due to their potential applications. We numerically investigate the properties of the two-dimensional curved surface metamaterial in the microwave regime. Unlike one-dimensional planar metamaterial, some novel properties are stimulated in the designed two-dimensional curved surface metamaterial. The reflected wave is transformed into its orthogonal polarization wave in addition to the absorbing components for normal linearly polarized electromagnetic wave incidence. The polarization conversion ratio and absorption are discussed detailly under different oblique incident conditions both in transverse electric wave and transverse magnetic wave. The reflections are stable for transverse magnetic wave while changing obviously for transverse electric wave when the incident angle changes from 0° to 60°. The tendency of reflections is almost consistent when the polarization angle changes from 0° to 45° under normal incidence. We also discuss the influences of the geometric parameters on the properties of the two-dimensional curved surface metamaterial. The designed two-dimensional curved surface metamaterial can be a very potential candidate for the radar scattering section reduction and electromagnetic stealth.

Scattering from a cylindrical obstacle deeply buried beneath a planar non-integer dimensional dielectric slab using Kobayashi potential method

Mathematical formulation for the far-zone field scattered by a cylindrical obstacle deeply buried beneath a planar dielectric slab has been presented. Method known as Kobayashi potential method has been employed for this purpose and transverse electric uniform plane wave has been used as a source of excitation. It has been assumed that dimension of space within slab is non-integer in the direction normal to planar interfaces of the slab. Moreover, it has also been assumed that distance of each interface of the slab from obstacle is very large as compared to size of the obstacle. Due to this assumption scattered field after reflection from the slab has no interaction with the obstacle and the situation has been called deeply buried. Field pattern has also been obtained and compared with the published work.

On the existence of infinitely many nonperturbative solutions in a transmission eigenvalue problem for nonlinear Helmholtz equation with polynomial nonlinearity

The paper focuses on a transmission eigenvalue problem for nonlinear Helmholtz equation with polynomial nonlinearity which describes the propagation of transverse electric waves along a dielectric layer filled with nonlinear medium. It is proved that even if the nonlinearity coefficients are small, the nonlinear problem has infinitely many nonperturbative solutions, whereas the corresponding linear problem always has a finite number of solutions. This results in the theoretical existence of a novel type of nonlinear guided waves that exist only in nonlinear guided systems. Asymptotic distribution of the eigenvalues is found and a comparison theorem is proved; periodicity of the eigenfunctions is proved, the exact formula for the period is found, and the zeros of the eigenfunctions are determined. The results found essentially extend the theory evolved earlier (particular cases for Kerr, cubic-quintic, septic nonlinearities, etc. are easily extracted from the general results found here). Numerical results are also presented.