Propagation Of Electromagnetic Surface Waves Research Articles

Comment on: “Tunable surface waves supported by graphene-covered left-handed material structures” [Opt. Commun. 489 (2021) 126874

In a recent article (Yaqoob et al., 2021), Yaqoob et al. studied the tunable electromagnetic surface wave propagation on the graphene-covered left-handed material (LHM) slab backed by the perfect electric conductor (PEC). They derived the dispersion relations for both transverse electric (TE) and transverse magnetic (TM)-polarized surface waves, and then used the relations for two types of LHMs according to the spectral range, i.e., GHz- and THz-LHM. The present Comment points out although the system under consideration (i.e., graphene-covered LHM) is itself physically challenging, the results for THz-LHM are also rather unreal because the frequency regime to accomplish the calculations falls within the high THz frequency band. In such a frequency band, the conductor substrate no longer behaves like a PEC and thus the results are rather unreal when considering THz-LHM. We note that the metal, for example, gold or silver may be modeled as a PEC, but only for a few THz. Moreover, when considering GHz-LHM, we obtain new forms of dispersion relations for both TE and TM surface waves. We find that our dispersion relations do not agree with the results obtained by Yaqoob et al.

Nonreciprocal propagation of surface electromagnetic waves in structures comprising magneto-optical materials

This paper investigates theoretically the effect of nonreciprocity on surface electromagnetic waves (SEWs) propagating in magneto-optical structures in mutually opposite directions, i.e., on waves with tangential wave numbers $k$ of opposite sign. Namely, of our interest is a correlation between the numbers of forward ($k>0$) and backward ($k<0$) propagating SEWs, which manifests itself as a limit on the total number of SEWs. The peculiarity of this limit is that the maximum total number of forward- and backward-propagating SEWs is less than the sum of the maximum numbers of SEWs for each of the opposite directions taken individually. We derive a relation between the electromagnetic surface impedances relevant to forward- and backward-propagating waves. Afterward, by using general properties of these impedances valid regardless of the crystallographic symmetry, we analyze the roots of dispersion equations without solving them explicitly. Various types of magneto-optical structures are considered. In particular, it is shown that, in the bicrystal formed of two half-infinite magneto-optical media, the maximum total number of forward- and backward-propagating SEWs is two at a given value of $|k|$, whereas in each of the mutually opposite directions two SEWs can exist. For example, if two forward-propagating SEWs are known to exist, then no backward-propagating SEW exists. In the case where a metal film is inserted between two different half-infinite magneto-optical media, the maximum number of SEWs in one direction is four but the maximum of the total number of forward- and backward-propagating SEWs is six rather than eight.

Simulation of nonlinear standing wave excitation in very-high-frequency asymmetric capacitive discharges: roles of radial plasma density profile and rf power

It is recognized that in large-area, very-high-frequency capacitively coupled plasma (VHF CCP) reactors, the higher harmonics generated by nonlinear sheath motion can lead to enhanced standing wave excitation. In this work, a self-consistent electromagnetic model, which couples a one-dimensional, radial nonlinear transmission line model with a bulk plasma fluid model, is employed to investigate the nonlinear standing wave excitation in a VHF driven, geometrically asymmetric capacitive argon discharge operated at low pressure. By considering a radially non-uniform plasma density profile (case I) calculated self-consistently by the nonlinear electromagnetic model and the corresponding radially-averaged, uniform plasma density profile (case II), we first examine the effect of the plasma density non-uniformity on the propagation of electromagnetic surface waves in a 3 Pa argon discharge driven at 100 MHz and 90 W. Compared to case II, the higher plasma density at the radial center in case I determines a higher plasma series resonance frequency, yielding stronger high-order harmonic excitations and more significant central peak in the harmonic current density J z,n and the harmonic electron power absorption p n profiles. Therefore, under the assumption of the radially uniform plasma density in a CCP discharge, the self-excitation of higher harmonics at the radial center should be underestimated. Second, using the self-consistent electromagnetic model, the effect of the rf power on the excitation of nonlinear standing waves is investigated in a 3 Pa argon discharge driven at 100 MHz. At a low power of 30 W, the discharge is dominated by the first two harmonics. The higher harmonic excitations and the nonlinear standing waves are observed to be enhanced with increasing the rf power, resulting in a more pronounced central peak in the radial profiles of the total electron power absorption density p e, the electron temperature T e, and the electron density n e. For all rf powers, the calculated radial profiles of n e show good agreement with the experimental data obtained by a floating double probe.

Electromagnetic Energy Surface Modes in Metamaterial-Filled Bi-layer Graphene Structures

This paper presents a theoretical study on the propagation of electromagnetic surface waves supported by the metamaterial-filled bi-layered graphene structure. The effective surface conductivity approach based upon the Kubo’s formalism is used to model the atomically thick graphene layer, while the analytical modeling of the metamaterials used the framework of causality principle-based Kramers-Kroing relations. With respect to the index of refraction, the two configurations of metamaterials have been considered—i.e., double positive (DPS) and double negative (DNG). The impedance boundary conditions (IBCs) have been employed at the interface for the computation of characteristics equations of odd and even surface modes under DPS and DNG configurations. The numerical results regarding the dispersion relations, effective mode index, and phase speed for the odd and even modes of electromagnetic surface waves supported by each configuration of structure have been presented. Further, the influence of chemical potential and thickness of metamaterial filling in parallel graphene layers on the wave propagation characteristics has been analyzed. To check the accuracy of the numerical results, special conditions were employed, which converge to the published results. The proposed work may have potential applications in plasmonic based logic designs, renewable energy devices, THz surface wave guides, and near-field communication devices.

SLOW SURFACE ELECTROMAGNETIC WAVES AT THE METASURFACE / DISSIPATIVE DIELECTRIC INTERFACE

The possibilities of the slow surface electromagnetic waves propagation along the flat boundary of a metasurface with a dissipative dielectric are studied. The metasurface is a thin flat slab of metamaterial with simultaneously negative permittivity and permeability with "amplification". All media were assumed to be isotropic. Dispersion dependences are obtained for the eigenmodes of such a waveguide structure. The possibility of full compensation of the energy losses of surface waves by the appropriate choice of the “gains” values is demonstrated.

Development of Broadband Underwater Radio Communication for Application in Unmanned Underwater Vehicles

This paper presents several novel designs of small form factor underwater radio antennas operating in the 2 MHz, 50 MHz and 2.4 GHz bands. These antennas efficiently excite surface electromagnetic waves (SEW) which propagate along the surface of seawater. The antenna operation is made possible due to implementation of an impedance matching enclosure, which is filled with de-ionized water. Enhanced coupling to surface electromagnetic waves is enabled by the enhancement of the electromagnetic field at the antenna apex. These features allow us to make antenna dimensions considerably smaller compared to typical free space designs. They also considerably improve coupling of electromagnetic energy to the surrounding seawater. Since SEW propagation length is considerably larger than the skin depth in seawater, this technique is useful for underwater broadband wireless communication. We conclude that the developed broadband underwater radio communication technique will be useful in networking of unmanned underwater vehicles.

Surface waves with negative phase velocity supported by temperature-dependent hyperbolic materials

A numerical investigation was undertaken to elucidate the propagation of electromagnetic surface waves guided by the planar interface of two temperature-sensitive materials. One partnering material was chosen to be isotropic and the other to be anisotropic. Both partnering materials were engineered composite materials, based on the temperature-sensitive semiconductor InSb. At low temperatures the anisotropic partnering material is a non-hyperbolic uniaxial material; as the temperature is raised this material becomes a hyperbolic uniaxial material. At low temperatures, a solitary Dyakonov wave propagates along any specific direction in a range of directions parallel to the planar interface. At high temperatures, up to three different surface waves can propagate in certain directions parallel to the planar interface; one of these surface waves propagates with negative phase velocity (NPV). At a fixed temperature, the range of directions for NPV propagation decreases uniformly in extent as the volume fraction of InSb in the isotropic partnering material decreases. At a fixed volume fraction of InSb in the isotropic partnering material, the angular range for NPV propagation varies substantially as the temperature varies.

Surface plasmon polariton in multilayered configuration

We investigate the effect of a propagation of surface electromagnetic waves along a metallic surface covered by layered dielectric structures. The optical coupling of a wave incident to collective oscillations of electrons along an interface between a metal and a dielectric is governed by the thickness of metal and gap layers. The surface Plasmon excited by an electromagnetic wave with a central wavelength of λ=486 nm and using the optic finite-difference time-domain method (OptiFDTD). For the metal, in particular a frequency on their dielectric permittivity dependence and described by the Drude-Lorentz model and using the effective-index approach and an explicit expression for the propagation constant of long rang surface plasmon polaritons (LR-SPPs) obtained for moderate metal widths.

Electromagnetic surface waves guided by the planar interface of isotropic chiral materials

The propagation of electromagnetic surface waves guided by the planar interface of two isotropic chiral materials, namely materials $\calA$ and $\calB$, was investigated by numerically solving the associated canonical boundary-value problem. Isotropic chiral material $\calB$ was modeled as a homogenized composite material, arising from the homogenization of an isotropic chiral component material and an isotropic achiral, nonmagnetic, component material characterized by the relative permittivity $\eps_a^\calB$. Changes in the nature of the surface waves were explored as the volume fraction $f_a^\calB$ of the achiral component material varied. Surface waves are supported only for certain ranges of $f_a^\calB$; within these ranges only one surface wave, characterized by its relative wavenumber $q$, is supported at each value of $f_a^\calB$. For $\mbox{Re} \lec \eps_a^\calB \ric > 0 $, as $\left| \mbox{Im} \lec \eps_a^\calB \ric \right|$ increases surface waves are supported for larger ranges of $f_a^\calB$ and $\left| \mbox{Im} \lec q \ric \right|$ for these surface waves increases. For $\mbox{Re} \lec \eps_a^\calB \ric < 0 $, as $ \mbox{Im} \lec \eps_a^\calB \ric $ increases the ranges of $f_a^\calB$ that support surface-wave propagation are almost unchanged but $ \mbox{Im} \lec q \ric $ for these surface waves decreases. The surface waves supported when $\mbox{Re} \lec \eps_a^\calB \ric < 0 $ may be regarded as akin to surface-plasmon-polariton waves, but those supported for when $\mbox{Re} \lec \eps_a^\calB \ric > 0 $ may not.

Bloch surface waves at the telecommunication wavelength with lithium niobate as the top layer for integrated optics.

Lithium niobate (LN)-based devices are widely used in integrated and nonlinear optics. This material is robust and resistive to high temperatures, which makes the LN-based devices stable, but challenging to fabricate. In this work, we report on the design, manufacturing, and characterization of engineered dielectric media with thin-film LN (TFLN) on top for the coupling and propagation of electromagnetic surface waves at telecommunication wavelengths. The designed one-dimensional photonic crystal (1DPhC) sustains Bloch surface waves (BSWs) at the multilayer-air interface at 1550nm wavelength with a propagation detected over a distance of 3mm. The working wavelength and improved BSW propagation parameters open the way for exploration of nonlinear properties of BSW-based devices. It is also expected that these novel devices potentially would be able to modify BSW propagation and coupling by external thermal-electrical stimuli due to the improved quality of the TFLN top layer of 1DPhC.

On Observation of Surface Electromagnetic Waves in Enclosed Spaces

An experiment on the study of waveguide propagation of surface electromagnetic waves with a frequency of 1 GHz in an enclosed space on free curved metal–dielectric interface was conducted. The distribution of the field of the electromagnetic wave along the propagation path was obtained for two cases: when a metallized tape was placed between radiating and receiving antennas and without the tape. It has been found that the field strength in the presence of the metallized tape is higher than the field strength without the tape.

Excitation and Propagation of Sommerfeld–Zenneck Surface Waves on a Conducting Strip in the Centimeter-Wave Band

The paper presents the results of experimental studies and the analysis of the surface electromagnetic wave propagation along metal conducting strips in the centimeter-wave band, which is convenient for simulation of open waveguides for the optical and terahertz bands of electromagnetic radiation.

Temperature-mediated transition from Dyakonov–Tamm surface waves to surface-plasmon-polariton waves

The effect of changing the temperature on the propagation of electromagnetic surface waves (ESWs), guided by the planar interface of a homogeneous isotropic temperature-sensitive material (namely, InSb) and a temperature-insensitive structurally chiral material (SCM) was numerically investigated in the terahertz frequency regime. As the temperature rises, InSb transforms from a dissipative dielectric material to a dissipative plasmonic material. Correspondingly, the ESWs transmute from Dyakonov–Tamm surface waves into surface-plasmon-polariton waves. The effects of the temperature change are clearly observed in the phase speeds, propagation distances, angular existence domains, multiplicity, and spatial profiles of energy flow of the ESWs. Remarkably large propagation distances can be achieved; in such instances the energy of an ESW is confined almost entirely within the SCM. For certain propagation directions, simultaneous excitation of two ESWs with (i) the same phase speeds but different propagation distances or (ii) the same propagation distances but different phase speeds are also indicated by our results.

Optical and structural properties of amorphous silicon-nitrides and silicon-oxycarbides: Application of multilayer structures for the coupling of Bloch Surface Waves

Hydrogenated amorphous silicon nitrides (a-SiNx:H) and oxycarbides (a-SiOxCy:H) have been grown by means of plasma enhanced chemical vapor deposition (PECVD) at a low power density (40–60mW/cm2) using silane, ammonia, methane and carbon dioxide as silicon, nitrogen, carbon and oxygen precursors, respectively. Their refractive index dispersion curves have been analyzed by means of specular reflectance spectroscopy and their structural properties by FTIR spectroscopy. Taking advantage of their optical properties, the alloys have been fruitfully applied in dielectric stratified structures, optimized for the propagation of surface electromagnetic waves.

Temperature-mediated transition from Dyakonov surface waves to surface-plasmon-polariton waves

The propagation of electromagnetic surface waves, guided by the planar interface of a temperature-sensitive isotropic material and a temperature-insensitive uniaxial material, each characterized by a relative permittivity dyadic, was investigated theoretically for the case of the optic axis of the uniaxial partnering material lying wholly in the interface plane. On raising the temperature, the isotropic partnering material (namely, InSb) transforms from a weakly dissipative dielectric material to a metal in the terahertz frequency regime. Correspondingly, the surface waves change from being Dyakonov surface waves to being surface–plasmon–polariton (SPP) waves. Numerical studies revealed that modest changes in temperature could result in dramatic changes in the numbers of propagating surface waves, their angular existence domains, their propagation constants, and their decay constants. Whereas multiple Dyakonov surface waves may propagate in a specific direction if at least one of the two partnering materials is dissipative, at most one SPP wave can propagate in a specific direction.

Electromagnetic surface waves on a conducting cylinder

We study propagation of electromagnetic surface waves on a metal-air interface in the case when the wave frequency is below the plasma frequency. We derive a reduced wave equation for a metal cylinder with a given radius of curvature. Using the Leontovich boundary condition we find solutions to this equation which we classify as outgoing and incoming surface waves. We derive the dispersion relations of the surface waves of both types and argue that the earlier studies overlooked the waves of the second type although they are the only type which can propagate on a planar metal-air boundary.

Ultrahigh-frequency surface electromagnetic waves in an open waveguide

An experiment in which guided propagation of surface electromagnetic waves (SEWs) on a free curved metal-dielectric interface was observed in the ultrahigh-frequency band (at frequencies of 850 and 1200 MHz) is described. The data on signal propagation over various paths and under various propagation conditions is presented. It has been found that the decrease of the wave field with increasing distance from the source follows the exponential law.

Surface states in photonic crystals

Among many unusual and interesting physical properties of photonic crystals (PhC), in recent years, the propagation of surface electromagnetic waves along dielectric PhC boundaries have attracted considerable attention, also in connection to their possible applications. Such surfaces states, produced with the help of specialized defects on PhC boundaries, similarly to surfaces plasmons, are localized surfaces waves and, as such, can be used in various sensing applications. In this contribution, we present our recent studies on numerical modelling of surface states (SS) for all three cases of PhC dimensionality. Simulations of these states were carried out by the use of plane wave expansion (PWE) method via the MIT MPB package.

Measurements of electromagnetic surface wave propagation in the cut‐off frequency region

AbstractElectromagnetic surface wave propagation on a corrugated metal plate is confirmed by a cold test in the X‐band. The measured cut‐off frequency is almost in agreement with the theoretical cut‐off frequency. The propagation is damped at a frequency region higher than the cut‐off frequency. The periodicity of the propagation power to the frequency is confirmed. For the confirmation of these characteristics, it is necessary that the corrugated metal plate is enclosed within a microwave absorber. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Surface electromagnetic waves in thin-layer biaxial structure in a magnetic field

The conditions for the existence of surface electromagnetic waves at the planar interface between a homogeneous medium (vacuum) and a thin-layer periodic structure consisting of alternating semiconductor and dielectric layers in an external magnetic field have been investigated. This structure represents an optically biaxial crystal with the effective permittivity tensor components dependent both on the geometric parameters of the structure and on the physical characteristics (magnetic field strength, frequency, and thicknesses of the layers). It has been shown that the propagation of surface electromagnetic waves localized near the interface can occur in the thin-layer biaxial structure within specific ranges of frequencies and external magnetic field strengths.