Transverse Electric Surface Research Articles

Simultaneous TE and TM designer surface plasmon supported by bianisotropic metamaterials with positive permittivity and permeability

Abstract Surface plasmon polaritons (SPPs) are surface modes existing at the interface between a metal and a dielectric material. Designer SPPs with a customer-defined property can be supported on the surface of suitably engineered metallic structures. They are important for various applications, ranging from chemical sensing to super-resolution imaging. In conventional systems, SPPs are transverse magnetic (TM) polarized, because of their origin in the collective electron oscillation along the surface. In this work, we show that both transverse electric (TE) and TM designer surface plasmons can be supported at the interface between a suitably designed bianisotropic metamaterial and a normal dielectric material without involving either negative permittivity or negative permeability. We further propose a realistic bianisotropic metamaterial for implementation of the double surface modes. The bianisotropic metamaterial demonstrated here may have tremendous applications in optical information processing and integrated photonic devices.

Spatially dispersive dichroism in bianisotropic metamirrors

Dichroism refers to the differential absorption of a material for different polarized waves and has important applications in polarimetry and optical wavefront manipulation. The coexistence of strong linear and circular dichroism at thin optical interfaces is usually challenging due to the weak chiral anisotropy in natural materials. Here, we investigate the spatially dispersive dichroism of bianisotropic metamirror, in which giant linear and circular dichroism can be achieved simultaneously. By covering the metallic mirror with an array of bianisotropic resonators, specific linearly and circularly polarized waves can be largely absorbed under normal and oblique incidences, respectively. This intriguing phenomenon is attributed to the anisotropic magneto-electric coupling, that is, the handedness and the strength of the equivalent transverse electric surface current are determined by the angle of incidence. Furthermore, dual-band and hybrid-chirality metamirrors for asymmetric spin reflection have been realized by adjusting the geometries and arrangement of the bianisotropic resonators. The overall thickness of the bianisotropic metamirror is only 1/50 of the wavelength and thus highly suitable for on-chip integration. Our findings may provide an alternative approach towards multifunctional optical mirrors, signal detectors, chiral imaging devices, and molecular analyzers.

Propagation of surface plasmon polaritons in monolayer graphene surrounded by nonlinear dielectric media

The propagation of s-polarized surface plasmon polaritons (SPPs) was investigated in a monolayer graphene sheet surrounded by two dielectric media on each side, so that one or both sides of the media were linear or nonlinear with Kerr-type nonlinearity. The plasmonic properties including the wave propagation index neff, the penetration depth, the time-averaged power flow and the spatial profile of electric and magnetic fields were calculated for the following structures: Linear medium/Graphene/Linear medium (L/G/L), Nonlinear medium/G/L (NL/G/L) and NL/G/NL. The analysis of the nonlinear coefficient effect on the SPP properties showed that increasing the nonlinearity in NL/G/L enhanced neff. However, for a smaller difference between the nonlinearity of layers, neff decreased in NL/G/NL. By comparing between the proposed structures, it was found that while large values of neff can be obtained from L/G/L, its frequency confinement is smaller than that of NL/G/L and NL/G/NL. Furthermore, NL/G/L and NL/G/NL were able to support localized nonlinear modes, leading to enhanced frequency confinement of transverse electric (TE) waves in the presence of nonlinearity. Increasing the nonlinearity in NL/G/L confined the spatial profile of the electric field near the graphene interface, indicating the existence of surface plasmon solitons. The influence of the graphene chemical potential μ on the plasmonic properties of the structures was also investigated. In this case, it was found that the plasmonic properties can be controlled by μ. Our calculations may solve the difficulties in TE surface plasmons for application in optics and plasmonics.

Characteristics of TE Surface Waves in a Plasma Medium Bounded by Nonlinear Metamaterials

The characteristics of nonlinear transverse electric surface waves are analyzed in a plasma medium bounded by Kerr-type double-negative metamaterials. In this connection, the electric and the magnetic field components, the dispersion relation, and the power flow in the direction of propagation are derived. The dispersion relation and the power flow are numerically analyzed for variations in different parameters of the guiding structure. We also examine the special cases for nonlinear single-negative metamaterials.

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 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.

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.

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.

Study on Glow Discharge in One-Dimensional Transverse Non-uniform Electric Field and Surface Processing of Aramid Fabric

Using a staggered contact electrode structure, the conditions for and mechanism of uniform discharge in one-dimensional transverse non-uniform electric field and with aramid fiber (AF) as a dielectric barrier material were explored for the first time in this study. An atmospheric pressure glow discharge (APGD) plasma was generated, and the large-area and continuous processing of AF was achieved. Through the electric field simulation as well as scanning electron microscope and X-ray photoelectron spectroscopy tests, it was found that the modification method of pressing the electrode closely to the AF could form the extremely strong electric field region of magnitude 1.444 × 107 V/m under the premise of uniform discharge. The highly active plasma generated could not only effectively increase the surface roughness of the treated material, but also introduce nitrogen functional groups which can’t be introduced through traditional air plasma. As found through the contact angle measurement, the contact angle was greatly decreased (by 52.3%) after being treated with 12.05 W/cm3 of plasma for 10 s, indicating that APGD plasma can achieve a good modification effect and high modification efficiency at low discharge power density.

Nonlinear TE surface waves in a ferrite slab bounded by Kerr-type metamaterials

In this paper, nonlinear transverse electric surface waves in a structure consisting of a ferrite slab sandwiched between a Kerr-type double-negative metamaterial (DNG-MTM) have been investigated. In addition to a DNG-MTM, two special cases with nonlinear single-negative metamaterials (SNG-MTMs) have also been discussed. The dispersion relations are obtained by applying the boundary conditions to the tangential field components of each layer. The propagation characteristics are plotted numerically for the effective wave index versus propagation frequency.

Chiral surface waves for enhanced circular dichroism

We present a novel chiral sensing platform that combines a one-dimensional photonic crystal design with a birefringent surface defect. The platform sustains simultaneous transverse electric and transverse magnetic surface modes, which are exploited to generate chiral surface waves. The present design provides homogeneous and superchiral fields of both handednesses over arbitrarily large areas in a wide spectral range, resulting in the enhancement of the circular dichroism signal by two orders of magnitude, thus paving the road toward the successful combination of surface-enhanced spectroscopies and electromagnetic superchirality.

Nonlinear TE-polarized SPPs on a graphene cladded parallel plate waveguide

We consider the transverse electric (TE) surface plasmon polaritons (SPPs) supported by a graphene parallel plate waveguide bounded by Kerr-type nonlinear media in the mid-infrared and terahertz frequencies. Through theoretical analysis of the exact dispersion relations, we reveal the existence conditions of the even mode and odd mode of nonlinear TE SPPs in this system. To be specific, if the linear permittivity of the nonlinear cladding is larger than the permittivity of the core, it only supports the even mode and two branches of the dispersion curve exist. However, when the linear permittivity of the nonlinear cladding is smaller than the permittivity of the core, both even and odd modes can be supported. Moreover, it is found that the propagation constant of even and odd modes decreases with the increasing Fermi energy of graphene.

Hybrid surface waves in two-dimensional Rashba-Dresselhaus materials

We address the electromagnetic properties of two-dimensional electron gas confined by a dielectric environment in the presence of both Rashba and Dresselhaus spin-orbit interactions. It is demonstrated that off-diagonal components of the conductivity tensor resulting from a delicate interplay between Rashba and Dresselhaus couplings lead to the hybridization of transverse electric and transverse magnetic surface electromagnetic modes localized at the interface. We show that the characteristics of these hybrid surface waves can be controlled by additional intense external off-resonant coherent pumping.

Broadband transverse electric surface wave in silicene

Transverse electric (TE) surface wave in silicine is theoretically investigated. The TE surface wave in silicene is found to exhibit better characteristics compared with that in graphene, in terms of a broader frequency range and more confinement to the surface which originate from the buckled structure of silicene. We found that even undoped silicene can support the TE surface wave. We expect the similar characteristics of the TE surface wave in other two-dimensional materials that have a slightly buckled honeycomb lattice.

Transverse electric surface mode in atomically thin Boron-Nitride.

The spatial confinement and the propagation length of surface waves in a single-layer two-dimensional atomic crystal are analyzed in terms of its surface susceptibility and its surface conductivity. Based on the values of these macroscopic parameters, extracted from experimental observations, it is confirmed that graphene supports a transverse magnetic nonradiating surface mode in the ultraviolet spectral region while a single-layer hexagonal Boron-Nitride is predicted to support a transverse electric nonradiating surface mode in the visible spectrum. This last mode, at a vacuum wavelength of 633 nm, has a spatial confinement of 15 μm and an intensity-propagation distance greater than 2 cm.

TE Surface Waves in a Plasma Sandwich Structure

Transverse electric surface waves are analyzed in a plasma medium bounded by a left-handed material. A dispersion relation is obtained by applying the boundary conditions for the tangential eld components. Numerical investigations show the dependence of e ective wave index on the propagation frequency for di erent thicknesses and number densities of the plasma medium and also for di erent values of the lling factor of left-handed material.

Supercoupling of surface waves withε-near-zero metastructures

It is known that $\ensuremath{\epsilon}$-near-zero (ENZ) structures may provide exciting possibilities for light-matter interaction, including the phenomenon of supercoupling, i.e., channeling of wave energy through ultranarrow conduits connecting two waveguides. Here, we extend this concept to the surface waves using structures with effective ENZ properties, exploring how surface waves can tunnel through such structures with essentially no reflection, even in the presence of sharp bends. Such ENZ metastructures support tunneling of waves with longitudinal wave numbers near zero. The surface waves may include examples of transverse electric (TE) surface waves along the grounded dielectric slabs (e.g., in the microwave regime) and TE surface-plasmon polariton waves along the negative-permeability interfaces. The ENZ metastructures can transfer the surface wave energy from one side to another by an anomalous squeezing effect, which is effectively independent of the length and the shape of the ENZ metastructures. The interaction of electromagnetic waves with such systems offers exciting possibilities for the design of flat photonic devices and components.

Transverse-electric surface plasmon for graphene in the Dirac equation model

Transverse-electric surface plasmon for graphene in the Dirac equation model