A 4-Bit Multistate Frequency-Selective Surface With Dual-Band Multifunction Response

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.

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 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.

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.

A simple analytical calculation scheme to determine near field radiation through decomposing an emission domain into lots of thin thermal current sheets is presented. Through finding the orthogonal modes of thermal current of each thin layer, the thin current sheets can be treated as radiation sources of electromagnetic waves with determined analytical solutions. The outgoing electromagnetic waves from each thin current sheets can be either in transverse electric (TE) or transverse magnetic (TM) modes depending on the orientations of the current in the thin current sheets with respect to the directions of amplitude modulations of the orthogonal modes. Electromagnetic waves arriving to a collection domain are related to the electromagnetic waves leaving from each thin current thermal sheet with transfer coefficients. Transfer coefficient for TE and TM waves can be determined analytically with transfer matrix method or scattering matrix methods. Compared with existing dyadic Green's function method, the new calculation scheme allows material and temperature variations along one direction of the emission domain based on determined analytical expressions of TE and TM waves leaving from each thin current sheets. The simple calculation scheme is especially useful in near field radiation of layered structures with different material such as hyperbolic material with negative refractive indices. With this new approach, we recovered analytical solutions of near field radiation between two semi-infinite domains with uniform temperature and derived closed form solution of near field radiation between two semi-infinite domains with temperature profiles with/without laminated structures.

Strong nonreciprocal thermal radiation of transverse electric wave in Weyl semimetal

A numerical procedure for the solution of electromagnetic scattering problems involving inhomogeneous dielectric cylinders of arbitrary cross section is discussed. The cases of illumination by both transverse magnetic (TM) and transverse electric (TE) plane waves are considered. The scattering problems are modeled via a hybrid integral-equation/partial-differential-equation approach. The method of moments is applied to obtain a system of simultaneous equations that can be solved for the unknown surface current densities and the interior electric field. The interior region partial differential equation and the exterior region surface integral equation are coupled in such a manner that many existing surface integral equation computer codes for treating problems involving scattering by homogeneous dielectric cylinders can be modified easily to generate the block of the matrix corresponding to the surface current interactions. The overall system matrix obtained using the method of moments is largely sparse. Numerical results are presented and compared with exact solutions for homogeneous and inhomogeneous circular cylinders.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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.

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.

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.

Unified homogenization of photonic/phononic crystals with first-band negative refraction

Perovskite microcavities have excellent photophysical properties for integrated optoelectronic devices, such as nanolasers. Imaging and controlling the photonic modes within the cavity are fundamentally important to understand and develop applications. Here, photoemission electron microscopy (PEEM) is used to image the photonic modes within optical microcavities with a nanometer-scale spatial resolution. From a CsPbBr3 microcavity, hybrid mode patterns are observed. Spatial frequency spectrum analysis on the patterns uncovers the characteristic cavity modes, which are modeled with transverse magnetic (TM) and transverse electric (TE) waves, and assigned to exciton-polariton modes. Based on this understanding, the light focus in a designed microcavity is imaged in real space and controlled by the light field polarization. The study confirms that the cavity modes in perovskites can be effectively observed by the PEEM technique under resonant excitation, which, in turn, promotes the design of optoelectronic devices based on perovskite microcavities.

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.

Polarization and incident angle independent metamaterial-based absorber (MA) which acts as a strong dual-band resonator is designed and constructed. Besides, a method to design single/dual- band MA is presented in detail. The proposed model is based on isotropic ring resonator with gaps and octa-star strip (OSS) which allows maximization in the absorption because of the characteristic features of the structure. Re∞ection and absorption responses are obtained both numerically and experimentally and compared to each other. Two maxima in the absorption are experimentally obtained around 90% at 4:42GHz for the flrst band and 99:7% at 5:62GHz for the second band which are in good agreement with the numerical simulations (95:6% and 99:9%, respectively). The numerical studies verify that the dual-band MA can provide perfect absorption at wide angles of incidence for both transverse electric (TE) and transverse magnetic (TM) waves. The proposed model can easily be used in many potential application areas such as security systems, sensors, medical imaging technology.