Analysis of Plasmonic Structure using Finite Element Method

In this paper, the two-dimensional Fourier transform and wave decomposition technique are used to transform Maxwell’s equation in transversely isotropic (TI) formation into two independent sets of transmission line equations about transverse magnetic (TM) wave and transverse electric (TE) wave. According to both transmission line theory and superposition principle, an improved transmission line method is advanced to simplify the computational process of TM wave and TE wave only by introducing the transmission line Green’s functions of the current source. Thus, the new algorithm and the new expressions of current source electromagnetic (EM) dyadic Green’s functions in frequency-wavenumber domain are established for realizing the efficient simulation of marine controlled-source electromagnetic (MCSEM) responses in the horizontally layered TI formation. On this base, the basic solutions of the transmission line Green’s functions and EM boundary conditions are utilized to derive the recursive formula of the generalized reflections and amplitudes of the TE and TM waves, and the analytic solutions of the Green’s functions in each bed are obtained. Then, by using Fourier inverse transform and Bessel integral formula, the MCSEM responses in frequency-spatial domain are expressed in the Sommerfeld integral form. A combination of the cubic spline interpolation with the Lommel integral is used to efficiently compute the MCSEM responses. Finally, we validate the modeling algorithm and investigate the influences of changes in operation frequency and anisotropic coefficient on the MCSEM response in the TI formation.

We investigate the characterization of defect modes in one-dimensional ternary symmetric metallo-dielectric photonic crystal (1DTSMDPC) band-gap structures. We consider the defect modes for symmetric model with respect to the defect layer. We demonstrate re∞ectance with respect to the wavelength and its dependence on difierent thicknesses and indices of refraction of dielectric defect layer, angle of incidence and number of periods for both transverse electric (TE) and transverse magnetic (TM) waves. Also, we investigate properties of the defect modes for difierent metals. Our flndings show that the photonic crystal (PC) with defect layer, made of two dielectrics and one metallic material, leads to difierent band-gap structures with respect to one dielectric and one metallic layer. There is at least one defect mode when we use dielectric or metallic defect layer in symmetric structure. And, the number of defect modes will be increased by the enhancement of refractive index and thickness of dielectric defect layer.

The polarization characteristics of Whispering-Gallery-Mode (WGM) fiber lasers based on evanescent-wave-coupled gain are investigated. For the laser gain is excited by side-pumping scheme, it is found that the polarization property of lasing emission is simply dependent on the polarized states of the pump beams. The polarization property of lasing emission depends on the propagating situation of the pump beams in an optical fiber if the laser gain is excited by evanescent-wave pumping scheme, that is, if the pump beams within the fiber are meridional beams, the lasing emission is a transverse electric (TE) wave that forms a special radial polarization emission. However, if the pump beams within the fiber are skew beams, both transverse magnetic (TM) and TE waves exist simultaneously in lasing emission that forms a special axially and radially mixed polarization emission. Pumped by skew beams, the wave-number differences between TE and TM waves are also investigated quantitatively, the results demonstrate that the wave-number difference decreases with the increase of the fiber diameter and the refractive index (RI) of the cladding solution. The observed polarization characteristics have been well explained based on lasing radiation mechanism of WGM fiber laser of gain coupled by evanescent wave.

A numerical method is given for calculating the dispersion relations and field distributions of stationary, nonlinear transverse magnetic (TM) waves guided by optical planar waveguides with intensity-dependent permittivities. The method can treat arbitrary linear permittivity profiles and arbitrary types of the nonlinearity, since it is based on a numerical integration of the nonlinear wave equation. Numerical results for TM waves guided by symmetric nonlinear film with linear claddings and the three-layer waveguide with a nonlinear cover are presented for different mechanisms of the nonlinearity and compared with those for transverse electric (TE) waves. The treated waveguide is weakly guiding and the nonlinearity is of the Kerr type. It is shown that under these assumptions, the dispersion relations for TM waves are similar to those for TE waves except for the power levels required for operation. The behavior of TM waves is little affected by the nonlinear mechanism. These features can be derived from the fact that the longitudinal electric-field component is fairly small compared with the transverse component. >

The theoretical study of microwave characteristics of a thin film of hydrogen plasma in carbon nanotubes, which were grown by iron-catalyzed high-pressure carbon monoxide disproportionation, is presented. The system is assumed to be illuminated by either a transverse magnetic (TM) or a transverse electric (TE) waves at an arbitrary angle of incidence to the film. By considering the interference effects because of multiple reflections between thin plasma layer interfaces, the reflectance, transmittance, and absorptance of microwave radiation at the plasma film are deduced and their functional dependence on the continuous changing of the angle of propagation and plasma thickness with fixed parameters of the system are studied. The simulation results show that for the present system, the interference effects lead to a sinusoidal variation of the reflected intensity and can greatly reduce the amount of reflection power, but the absorption power increases. In addition, it is found that the TE and TM waves have largely indistinguishable microwave absorption and transmission spectrums.

The problem is considered of representing the vacuum electromagnetic field of an arbitrarily orientated dipole as the superposition of coplanar transverse magnetic (TM) and transverse electric (TE) fields. The method is to express the dipole field as an angular spectrum of plane waves, and to introduce the appropriate representation of each plane wave of the spectrum. For a time-harmonic electric dipole, in the non-trivial case in which the components of the magnetic and electric vectors, respectively, of the TM- and TE-fields vanish in a direction perpendicular to the dipole, the TM- and TE-fields are given explicitly in terms of elementary functions.

By using the transfer matrix method, the theoretical investigation has been carried out in the near- and mid-infrared bandgaps for a periodic multilayered structure that was composed of superconductor (SC) and semiconductor-metamaterial. It was found that two bandgaps appeared within the computational regions which are effectively optimized by manipulating the thickness of the SC film, fill factor of the semiconductor-metamaterial and the incidence angle of the incident electromagnetic wave. However, the thickness of the SC film and fill factor of the semiconductor-metamaterial are responsible for the red-shift of bandgaps, while the blue-shift is accounted for by the angle of incidence for both transverse electric (TE) and transverse magnetic (TM) waves. It is notable, for the TM wave, that the bandgaps disappeared at the incident angles of approximately 60[Formula: see text]. Such properties are quite useful in designing any new types of edge filters and other optical devices in the near- and mid-infrared frequencies.

In this letter, a novel 4 b multistate frequency-selective surface is proposed. Four p-i-n diodes are used to maneuver multifunction behavior of the structure with seven different functional states. The 4 b binary state operations 0000, 1100, 0011, and 1111 offer transverse electric (TE)/transverse magnetic (TM) waves both transmit, TE transmit/TM shield, TM transmit/TE shield, and TE/TM both shield, respectively, at 2 GHz frequency. The passband at 2 GHz frequency has <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-\text{10}$</tex-math></inline-formula> dB fractional bandwidth of 117%. The binary states 1101 and 1110 are symmetric, which select the TE wave transmit/TM wave shield to the passband at 3.45 GHz frequency with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-\text{10}$</tex-math></inline-formula> dB fractional bandwidth of 49%, whereas binary states 1011 and 0111 allow the TM wave to transmit at 3.45 GHz and shield the TE wave. The four symmetric binary states 0101, 0110, 1010, and 1001 provide transmission band at 3.45 GHz frequency for dual-polarized plane wave incidence. The transmission of both the passbands can be shielded by selecting the binary state equal to 1111. An equal circuit model is used to elaborate the contribution of different passive structural elements in terms of lumped components. A prototype of the structure is fabricated, and transmission coefficients for different states at normal and oblique incidence of the electromagnetic plane wave are measured, which verifies the simulated responses of the structure.

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.

An approach to obtain easy-to-fabricate and spectrally selective nonreciprocal thermal emitter (NTE) has been proposed. The presented hybrid structure is composed of Weyl semimetal (WSM) film sandwiched by Ge/BaF2/Ge tri-layer and metal substrate. It has been shown that structural parameters hold tolerance on the order of hundreds of nanometers, which are highly favorable for fabricating with low cost and high performance. Multiband responses of the device can be realized through controlling the thickness of last Ge layer, which boosts the flexibility of preparation and potential applications. The giant nonreciprocity can be maintained with broad polar and azimuthal angle ranges. By manipulating the structural parameters, a remarkable result of nonreciprocal radiation is realized under both the transverse electric (TE) and transverse magnetic (TM) wave incidence. By changing the azimuthal angle (ϕi) of incidence, the nonreciprocity (η) can be effectively manipulated. The simulated η spectra is symmetric along the azimuthal angle ϕi=90°, and η=0 when ϕi=90°. Our results provide a much simpler way to achieve the multi-channel nonreciprocity and could lead to the advancement of power scavenging and conversion devices.

Electrical failures in avionics systems may result from connector faults. If fault precursors are not detected in advance, they may lead to hard failures such as open and short circuits that could ultimately result in fire or loss of flight critical systems. Therefore, It is crucial to detect, locate, and characterize fault precursors for timely preventive maintenance and mitigation before hard failures occur. In this paper, a physics‐based connector model consisting of multiple coaxial line sections with different characteristic impedances and lengths is proposed. Method of Moments (MoM) analyses were performed using commercial electromagnetic simulation software, FEKO, for transverse electric and magnetic (TEM) wave propagation through a connector. The physical parameters of the connector were optimized to match the measured S parameters for multiple insertion depths. The proposed models represent the connector for multiple insertion depths by varying only two length parameters at a time while other parameters are fixed. Insertion depth‐dependent resonant frequency shifts observed during measurement are also captured by the model over the full range of fully inserted to barely touching contacts. Hence, the models provide accurate representations of the connector and properly detect precursors to partial insertion faults.

Strong nonreciprocal thermal radiation of transverse electric wave in Weyl semimetal

A wide-angle, wideband, and polarization-insensitive metamaterial (MM) absorber was studied based on the theoretical concept of uniaxial perfect matching layer (UPML) in the terahertz range. The MM absorber was designed as a multi-layered anisotropic array structure consisting of a conductive VIA, a bi-layered slot-FSS, and a split-ring resonator (SRR) separated by porous silica spacers. Each component is optimized to approach the required macroscopic uniaxial property for satisfying the reflection-less boundary condition. The SRRs and VIAs were found to play an important role in maintaining large absorption when the angle of oblique incidence increases under transverse electric (TE) and transverse magnetic (TM) polarization, respectively. The absorption achieves 90% in the frequency regime of 0.9 to 10.5 THz, corresponding to a bandwidth of 168% to the central frequency, and retains such high performance up to 60° oblique incidence for both TE and TM waves.

대규모 PEC 물체의 표면에 존재하는 Gap/Crack 구조에 의한 산란파는 RCS가 매우 낮은 물체에 있어서 그 중요성이 매우 크지만, 고주파 근사법을 사용하여 해석할 수가 없다. 만약 이들의 전기적 폭이 충분히 작다면, 적절한 임피던스 스트립으로 모델링 한 후, 저주파 근사법을 통하여 해석적으로 산란파 공식을 얻을 수 있다. 저주파 공식은 TE(Transverse Electric)파와 TM(Transverse Magnetic)파에 대해 2차원 해의 형태로 주어지며, 이를 바탕으로 3차원 ILDC(Incremental Length Diffraction Coefficients)를 추출할 수 있고, 이를 통하여 물체 표면에 존재하는 임의의 형태의 크랙의 산란파도 계산할 수 있다. 기존의 방법은 TE파에 의한 결과만을 사용하여, TM파가 중요한 경우에 정확도가 떨어진다. 본 논문에서는 TE파와 TM파에 의한 결과를 동시에 사용하여 향상된 ILDC 수식을 제안하고, 그 정확성을 시뮬레이션을 통하여 검증한다. The scattered field by a gap/crack on the PEC surface of a large object having low-observable RCS cannot be negligible, but may not be analyzed by the known high-frequency technique. If the electrical width of the crack is very small, the crack can be modeled by an impedance strip, whose scattering formulation can be analytically obtained based on a low-frequency approximation. The scattering solution is formulated for the 2D strip and TE(Transverse Electric) or TM(Transverse Magnetic) wave incidence, from which a 3D ILDC(Incremental Length Diffraction Coefficients) can be extracted. Using the ILDC formulation, the scattering by any arbitrary shaped crack can be estimated. In this paper, an improved ILDC equations are proposed, which combine the known TE and TM solutions. The improved accuracy of the proposed solution is numerically verified.

A simple design of metamaterial absorber (MA) was proposed based on a periodic array of metal patch at microwave frequencies. Our design could exhibit absorption of 99.9% confirmed by numerical simulation. Such high narrowband absorption which mainly based on strong electric and magnetic resonances overlapping in a certain frequency range and perfect impedance-matched (z = 1) to the free space. Numerical simulations demonstrate that the MA could achieve very high absorptivity at wide angles of incidence for both transverse electric (TE) wave and transverse magnetic (TM) wave. The absorption band of our device is effectively extended by patterning multi-square patches of different dimension elements with appropriate geometrical parameters in a co-planar. Finally, the composite MA is only 0.4 mm thick, with a maximum absorption of 99.8% at 15.8 GHz, and a full width at half maximum (FWHM) bandwidth of 2 GHz by numerical simulation, which may have potential applications in the detection of explosives and stealth.