Surface Electromagnetic Waves Research Articles

Multifrequency optimization method of measurement the frequency dependency of electrophysical parameters of dielectric and magnetodielectric coatings

The issues of experimental determination of electrodynamic parameters of existing and new synthesized materials and coatings used in the microwave range are highlighted. Problems arising from measurements of the electrophysical and geometric parameters of dielectric and magnetodielectric coatings, taking into account their placement on a metal substrate, by radio wave methods are considered. We present the new radio wave method of joint measurements of the frequency dependence of the complex permittivity, the frequency dependence of the complex magnetic permeability, and the thickness of plane-layered samples of dielectric and magnetodielectric coatings on a metal substrate. Determination of electrophysical and geometric parameters of the coating in the proposed method is reduced to minimizing the objective function constructed based on the discrepancy between the experimental and design theoretical values of the attenuation coefficients of surface electromagnetic wave fields on a grid of discrete frequencies. The simulation model of measurements is shown, implemented on the basis of the electrodynamic modeling system CST Microwave studio (Simulia corporation, USA) and the Matlab system. The results of simulation are presented to determine the frequency dependences of the electrophysical parameters and the thickness of a sample of a radio-absorbing coating on a metal substrate. Errors in the estimates of permittivity and permeability in the measurement frequency band 9–13.5 GHz, which are no more than 10 % with a confidence level of 0.95 with a mean square deviation of the noise level of 0.006, have been obtained. The proposed method can be in demand in various science-intensive areas – microelectronic, aerospace, mechanical engineering, etc.

Расчет коэффициента пропускания симметричной полосковой линии и моделирование формы линии распространения поверхностной электромагнитной волны

Расчет коэффициента пропускания симметричной полосковой линии и моделирование формы линии распространения поверхностной электромагнитной волны

Fabricating Femtosecond Laser-Induced Periodic Surface Structures with Electrophysical Anisotropy on Amorphous Silicon.

One-dimensional periodic surface structures were formed by femtosecond laser irradiation of amorphous hydrogenated silicon (a-Si:H) films. The a-Si:H laser processing conditions influence on the periodic relief formation as well as correlation of irradiated surfaces structural properties with their electrophysical properties were investigated. The surface structures with the period of 0.88 and 1.12 μm were fabricated at the laser wavelength of 1.25 μm and laser pulse number of 30 and 750, respectively. The orientation of the surface structure is defined by the laser polarization and depends on the concentration of nonequilibrium carriers excited by the femtosecond laser pulses in the near-surface region of the film, which affects a mode of the excited surface electromagnetic wave which is responsible for the periodic relief formation. Femtosecond laser irradiation increases the a-Si:H films conductivity by 3 to 4 orders of magnitude, up to 1.2 × 10−5 S∙cm, due to formation of Si nanocrystalline phase with the volume fraction from 17 to 28%. Dark conductivity and photoconductivity anisotropy, observed in the irradiated a-Si:H films is explained by a depolarizing effect inside periodic microscale relief, nonuniform crystalline Si phase distribution, as well as different carrier mobility and lifetime in plane of the studied samples along and perpendicular to the laser-induced periodic surface structures orientation, that was confirmed by the measured photoconductivity and absorption coefficient spectra.

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.

Surface wave direction control on curved surfaces

Transformation optics (TO) has been recognized as an established scheme that can precisely manipulate electromagnetic surface wave propagations. Utilising the advantages of the TO technique, we proposed a TO device which can control the propagation direction of surface waves. The device is based on a generalized Eaton lens and can be realized on curved surfaces. Such a device can be composed of stacked ring layers, where the refractive index of each ring segment can be individually engineered. By engineering the refractive index, the stacked ring structure can guide the propagation direction of the surface wave. It may open a new door to manipulate surface wave propagation on demand.

Optical surface plasmons at a metal-crystal interface with the Drude-Lorentz model for material permittivity

The theory of surface electromagnetic waves (SEMWs) propagating at optical frequencies along the interface of an isotropic metallic plasma [e.g., gold (Au)] and a uniaxial crystal [e.g., Rutile (TiO2)] is revisited with the Drude-Lorentz (DL) model for the complex dielectric material permittivity (ϵp). The latter accounts for the contributions of both the intraband transitions of the free electrons and the multiple interband transitions of the bound electrons in metals. The propagation characteristics of the wave vectors and wave frequency of SEMWs, the hybridization factors, i.e., the amplitude ratios between the transverse-electric (TE) and transverse-magnetic (TM) modes in the isotropic metal, and between the ordinary and extraordinary modes in the uniaxial substrate are studied numerically. It is found that the results are significantly modified from those with the Drude model for ϵp, especially in the short-wavelength spectra (λ ≲ 500 nm) and with a small deviation of the orientation of the optical axis. The excitation of such SEMWs can have novel applications in transportation of EM signals in a specified direction at optical frequencies (∼PHz).

Evaluating the Accuracy of Reconstruction of the Electrical and Geometric Parameters of Multilayer Dielectric Coatings by a Multifrequency Radio-Wave Method for Slow Surface Electromagnetic Waves

One of the most important problems in the diagnostics of multilayer dielectric materials and coatings is the development of methods for quantitative interpretation of the results of monitoring the electrical and geometric parameters of these materials. Results are presented from a study of the potential informativeness of a multifrequency radio-wave method for slow surface electromagnetic waves for reconstruction of the electrical and geometric parameters of multilayer dielectric coatings. A simulation model is shown for evaluating the accuracy of reconstructing the electrical and geometric parameters of multilayer dielectric coatings. The model takes into account the electrical and geometric parameters of the coating, the level of noise in the measurement data, and the measurement bandwidth. Simulation modeling and experimental test data for the reconstruction of the relative dielectric constants and thicknesses of one- and two-layer equal-thickness dielectric coatings based on polymethyl methacrylate, ftoroplast (teflon) F-4D, and RO3010 for different values of the mean square deviation of the noise level in the measured attenuation coefficients for the field of a slow surface electromagnetic wave. The accuracy of the reconstruction of the geometric and electrical parameters of the layers is found to decrease as the number of estimated parameters and the noise level increase, as well as when the dielectric constant and thickness of the layers are reduced. Experimental data confirm the adequacy of the simulation model developed here. This model can be used for a specific measurement complex employing a multifrequency radio-wave technique for slow surface electromagnetic waves to estimate quantitatively the potential possible accuracy of reconstructing the geometric and electrical parameters of multilayer dielectric materials and coatings. A simulation model and experimental study of a multilayer dielectric coating show that for a measurement bandwidth of 1 GHz the errors in estimating the dielectric constants and thicknesses of the layers do not exceed 10% with a confidence coefficient of 0.95 for a mean square deviation of 0.003–0.004 in the noise level.

Hyperbolic surface waves on anisotropic materials without hyperbolic dispersion.

We theoretically analyze directional surface electromagnetic waves supported at an interface between an isotropic medium and anisotropic metal with effective uniaxial negative permittivity. We identify two types of surface wave solutions, resulting in unique hyperbolic dispersion in the wavevector space. Such anisotropic metal can be realized by alternating dielectric and metallic layers with deep subwavelength thicknesses or metallic nanowires in dielectric host. Such systems serve as a platform for many applications in nanophotonics.

Microwave Magnon-Plasmon-Polaritons in the Ferromagnetic Metal–Screened Insulator Structure

A possibility for surface magnon–plasmon–polaritons (SMPPs)–coupled microwave oscillations of magnetization, electron density, and electromagnetic field–to exist in real ferromagnetic metal–insulator–ideal non-magnetic metal structures has been analyzed theoretically. The developed theory predicts that the effective formation of SMPPs is possible only at certain values of the external dc magnetic field and must be accompanied by a shift in the characteristic frequency of the resonance plasmon-polariton systems. A theoretical estimation of the frequency shift for SMPPs in the structure “surface electromagnetic wave resonator made of permalloy–vacuum–ideal metal” gives a value of ±45 MHz for a resonator with a characteristic frequency of 10 GHz, which seems sufficient for this effect to be observed experimentally.

Electromagnetic surface waves supported by a resistive metasurface-covered metamaterial structure

This study examines the analytical and numerical solution of electromagnetic surface waves supported by a resistive metasurface-covered grounded metamaterial structure. To simulate the metamaterial, the Kramers–Kronig relation based on the causality principle is used, while the modeling of the resistive metasurface has been done by implementing the impedance boundary conditions. The analytical expressions for the field phasors of surface waves are developed for the transverse magnetic (TM) polarized mode and transverse electric (TE) polarized mode. The characteristic equations are computed for both modes, and the unknown propagation constant is evaluated numerically in the kernel. After computation, the dispersion curves, electric field profiles, effective mode index (N_{eff}), and phase speeds (v_{p}) are presented for both the TM and TE polarized modes. To study the tunability of surface waves, the influence of the thickness of the metamaterial slab (d), effective permittivity of the metamaterial (varepsilon_{1}), thickness of the resistive metasurface (t), and effective permittivity of the metasurface (varepsilon_{r}) on all the numerical results has been studied. However, the geometrical parameters are found to be more sensitive to the effective mode index (N_{eff}) and phase speed (v_{p}) of the surface waves. The results are consistent with the published results, which reflects the accuracy of the work. It is concluded that the appropriate choice of parameters can be used to achieve surface waves with the desired characteristics in the GHz range. The present work may have potential applications in surface waveguide design, surface wave speed controllers, surface communication devices, and light trapping configurations.

Localized surface electromagnetic waves in CrI3-based magnetophotonic structures.

Resulting from strong magnetic anisotropy two-dimensional ferromagnetism was recently shown to be stabilized in chromium triiodide, CrI3, in the monolayer limit. While its properties remain largely unexplored, it provides a unique material-specific platform to unveil its electromagnetic properties associated with coupling of modes. Indeed, trigonal symmetry in the presence of out-of-plane magnetization results in a non-trivial structure of the conductivity tensor, including the off-diagonal terms. In this paper, we study the surface electromagnetic waves localized in a CrI3-based structure using the results of ab initio calculations for the CrI3 conductivity tensor. In particular, we provide an estimate for the critical angle corresponding to the surface plasmon polariton generation in the Kretschmann-Raether configuration by a detailed investigation of reflectance spectrum as well as the magnetic field distribution for different CrI3 layer thicknesses. We also study the bilayer structure formed by two CrI3 layers separated by a SiO2 spacer and show that the surface plasmon resonance can be achieved at the interface between CrI3 and air depending on the spacer thickness.

Surface electromagnetic waves in anisotropic superlattices

This paper studies the existence of electromagnetic surface waves localized on a boundary of half-infinite periodic superlattices formed by an arbitrary periodic sequence of layers of homogeneous or functionally graded materials with generally anisotropic dielectric permittivity and magnetic permeability tensors. The geometry in question implies either two superlattices attached together to form a photonic bicrystal or else a superlattice in contact with vacuum or any other homogeneous dielectric or metal. Using the formalism of transfer and impedance matrices, a series of statements is proved on the maximum number of surface waves which may exist within a forbidden band at a fixed tangential wave number. This number embraces possible occurrences of surface waves in a given bicrystal and in its counterpart obtained by swapping the upper and lower superlattices. A maximum total number of surface waves in both these structures with an arbitrary arrangement of their unit cells is 2 in the lowest forbidden band (extending from zero frequency) and 4 in any upper forbidden band. The same statements apply to the case where one of the half spaces is occupied by a homogeneous material. A factor 2 smaller number of surface waves occur in a bicrystal composed of superlattices with a symmetric arrangement of unit cells. The existence considerations are further specialized for the surface waves with TE and TM polarizations.

Mid-IR photothermal measurement of substantial heat transport by surface waves of polar amorphous films supported on silicon

We present measurements of significant thermal diffusivity by surface electromagnetic waves of an ultra-thin polar and amorphous dielectric film deposited on silicon (Si). We used a photothermal-beam-deflection technique with a modulated mid-infrared heating source to excite and launch surface electromagnetic waves onto the surface of an amorphous silicon carbide (a-SiC) film deposited on Si and generate periodic temperature and refractive index gradients above the sample surface. These gradients are capable of periodically deflecting a probe beam, passing very close to the surface, at the modulation frequency of the heating beam. We have fitted the measured probe beam deflection to an analytical model for the mirage effect that takes into account the thermal anisotropy of the measured sample to infer the contribution of the surface electromagnetic waves of the a-SiC film to thermal diffusivity in the plane of the sample under study. We found that reducing the thickness of the a-SiC film promotes the interaction between the surface electromagnetic waves propagating on either side of the a-SiC film, which significantly enhances thermal diffusivity in the plane of the measured sample. We also found that in-plane thermal diffusivity by surface electromagnetic waves on an amorphous silicon carbide film a few nanometers thick is several orders of magnitude greater than thermal diffusivity by phonons in silicon. We believe that the results obtained provide a better understanding of the physics of electromagnetic waves confined to solid surfaces.

Control of the conducting surface by terahertz surface electromagnetic waves

The paper considers the possibilities of quality control of the conductive surface and detection of objects on it beyond the horizon, as well as microscopy of flat faces of semiconductor products using surface electromagnetic waves (SEWs) of the terahertz (THz) range. The conditions under which such methods of control can be implemented are determined; schemes of devices that implement such measurements are elaborated; estimates of the possibilities of the developed methods for monitoring metal and semiconductor products probed by monochromatic THz radiation in the form of SEWs are given.

Can the ghost imaging increase the lateral resolution of surface plasmon resonance microscopy?

Surface plasmon resonance (SPR) microscopy is one of the most sensitive optical label-free methods of microscopy. Nevertheless, it does not have a sufficiently high lateral resolution in comparison with other methods of optical microscopy. By analogy with the scattering medium, surface plasmon polaritons (SPPs) blur the observed area. To eliminate this disadvantage, we propose to adapt the method known as ghost imaging (GI), which is notable for its tolerance to environmental aberrations between an object and a camera. In this article, we propose a ghost imaging scheme for a surface plasmon resonance microscope using a pseudo-thermal radiation source. We make a fundamental analysis of the factors affecting the resolution capability of the ghost SPR microscopy. We claim that applying the ghost imaging method to SPR microscopy can improve its lateral resolution by eliminating uncorrelated with modulated radiation phase noise generated by the process of random re-emission of surface electromagnetic wave (SEW) from the site of excitation. In combination of factors, the ghost imaging method of SPR microscopy is potentially capable of becoming outstanding among other methods of microscopy of thin films.

Quality control of solid surfaces by the method of surface plasmon interferometry in the terahertz range

The article considers the possibility of controlling the quality of a conducting surface using a Michelson interferometer, in which the information carrier is surface plasmon-polaritons (a type of surface electromagnetic waves) of the terahertz range. It is shown that using such an interferometer, it is possible both to control the uniformity of the dielectric coating on the surface of a metal product, and to detect inhomogeneities on the controlled surface, as well as to evaluate their geometric and optical characteristics.

Estimating the Extent of Exfoliation of Dielectric and Magnetodielectric Coatings with Surface Microwaves

We present the results of a study that confirms the high efficiency of using surface microwaves in assessing the extent of exfoliation of dielectric and magnetodielectric coatings from a metal base. The complex coefficient of attenuation of the field of a surface electromagnetic wave along the normal to the coating surface is used as a parameter for estimating the extent of exfoliation. In contrast to the existing approaches, the developed electrodynamic measurement model takes into account the real and imaginary parts of the complex dielectric permittivity and magnetic permeability of the coating with allowance for their frequency dispersion; this improves the accuracy and reliability of estimating the extent of exfoliation. An algorithm is developed for estimating the extent of coating exfoliation based on the search for the maximum joint probability density of the coefficient of attenuation of the field of a surface electromagnetic wave measured at a set of frequencies. We introduce and substantiate a statistical limit of the resolution of two values of exfoliation; this makes it possible to evaluate the possibility of discriminating between two close values of exfoliation depending on the bandwidth of attenuation coefficient measurements, their number, and the signal-to-noise ratio. The structure of a measuring complex that implements the proposed approaches to exfoliation assessment is provided. Numerical and field experiments have shown the fundamental possibility of estimating the value of recorded values of exfoliation of dielectric and magnetodielectric coatings from a metal substrate with a thickness of 20 μm or less in the frequency band of 9–13.5 GHz.

Enhanced antioxidation and microwave absorbing properties of SiC/SiO2 coating on carbon fiber

In the manuscript, a uniform SiC/SiO2 coating was successfully prepared on the surface of carbon fiber by electrolytic plasma spraying method, which is beneficial to the dielectric loss and interfacial polarization. The antioxidation and absorption capacity of electromagnetic waves were greatly improved. The surface morphology, chemical composition, oxidation resistance and electromagnetic wave absorption properties of the coated carbon fibers were analyzed in detail. The effect of sample thickness on the electromagnetic wave loss was investigated in 2–18 GHz. The absorbing mechanism of the coated carbon fiber was discussed. The coated carbon fiber exhibits superior absorbing properties due to the synergistic effect of dielectric loss and reflection loss. The minimum reflection loss of − 11.6 dB at the thickness of 2.3 mm at 7.1 GHz. Meanwhile, the SiC/SiO2 coating on carbon fiber also has oxidation resistance, which was 28% higher than the bare sample.

Direct Visualization of Phase-Locking of Large Josephson Junction Arrays by Surface Electromagnetic Waves

Phase-locking of oscillators leads to superradiant amplification of the emission power. This is particularly important for development of THz sources, which suffer from low emission efficacy. In this work we study large Josephson junction arrays containing several thousands of Nb-based junctions. Using low-temperature scanning laser microscopy we observe that at certain bias conditions two-dimensional standing-wave patterns are formed, manifesting global synchronization of the arrays. Analysis of standing waves indicates that they are formed by surface plasmon type electromagnetic waves propagating at the electrode/substrate interface. Thus we demonstrate that surface waves provide an effective mechanism for long-range coupling and phase-locking of large junction arrays.

Spoof surface plasmon polaritons based microwave bandpass filter

AbstractRecently, Plasmonics and metamaterials have been receiving consideration. Spoof surface plasmon polaritons (SSPPs) are a type of electromagnetic surface wave that to a certain limit shares an analogous behavior with surface plasmon polariton (SPP) at microwave frequency domain. The significant point is that the dispersion relation of SSPP is principally controlled by the geometry of the pattern using plasmonic metamaterial. The motivation behind this work is to explore and implement the subwavelength propagation or nanoconfinement of wave beyond the diffraction limit using plasmonic metamaterial‐inspired SSPP structure in the microwave frequency domain. In this article, the conventional symmetric H‐shaped unit cell is modified into a new unit cell. Using this modified unit cell, a new SSPP structure is designed which provides broadband bandpass filter (BPF) characteristics. The measurement shows the passband of BPF is 1.2 to 6.0 GHz with insertion loss less than 2 dB. The size of the fabricated SSPP BPF is 26 × 4 cm.