ABSTRACT The unique advantages of porous materials with spatial arrangement have inspired the development of advanced microwave absorption (MA) materials. It is a good strategy to design pore sizes and a customized spatial arrangement for optimizing electromagnetic synergistic behaviors. Herein, a micro‐meso‐macropores structure with in‐plane multi‐components has been successfully constructed in carbon foam (CF). The innovative design is that the poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) film on CF not only serves as an in situ source of O and S anions for forming Co, CoO, and Co 9 S 8 phases through ion‐exchange and competitive reactions, but also effectively induces an in‐plane arrangement of carbon nanocoils and metal‐organic frameworks (MOFs). Experiments and simulations revealed a multi‐level collaborative attenuation mechanism spanning from macroscopic conductive loss to nanoscale polarization. More importantly, the in‐plane configuration of multi‐components further amplifies electromagnetic coupling. The optimized structure achieved excellent broadband absorption performance across a wide range of incidence angles. Furthermore, after an additional periodic structural design, the effective absorption bandwidth was expanded from 8 to 12 GHz, and the minimum reflection loss value was improved from −20.5 to −60 dB. Analysis indicates that the ultra‐broadband characteristics of the array microwave absorber originate from the synergistic regulation of electromagnetic cooperative effects and edge diffraction effects by the periodic structure.

Electromagnetic diffraction of slotted conductive strips is studied using the subdomain method. The subdomain method is based on the Green’s second identity, which decomposes the geometry into partially overlapping subdomains. In each subdomain, the electromagnetic fields are expressed as Fourier–Bessel series. When the field representations in the subdomains are incorporated into the original structure, discontinuities may appear at several interfaces. To address this, we introduce artificial line currents to eliminate the discontinuities. Fourier coefficients are determined by enforcing boundary conditions using the mode-matching method and the orthogonality of sinusoidal functions. To evaluate the accuracy of the subdomain method, we use the root-mean-square error of the surface current density and the bistatic scattering cross section. To assess the computational efficiency, we compare the elapsed time and allocated memory of the subdomain method with those of the finite element method. The numerical results demonstrate that the subdomain method provides solutions for the given geometry with high precision and efficiency.

The proliferation of hidden WiFi cameras has raised serious privacy concerns, making their accurate detection and localization essential for the secure development of future intelligent wireless networks. However, existing solutions often require substantial user involvement, large movement spaces, predefined system parameters, or pre-collected training data, limiting their practicality and scalability. In this paper, we present DiffLoc+, a novel and low-cost system that localizes hidden WiFi cameras by harnessing the fundamental physical principle of electromagnetic diffraction. When an obstacle crosses the line-of-sight path between a transmitter and a receiver, it causes a distinctive signal attenuation pattern. We theoretically analyze the feasibility of exploiting this phenomenon for localization and identify two key conditions for building an unbiased diffraction-based model: symmetry and observability. To satisfy these conditions, DiffLoc+ introduces a controllable diffraction generation mechanism that precisely rotates a small metal plate around a WiFi receiver (e.g. a Raspberry Pi), producing a stable and predictable diffraction “shadowing” effect. We then construct an unbiased localization model that maps this effect to the azimuth of the camera. To ensure the robustness of the theoretical model in real-world applications, DiffLoc+ further introduces two robustness-enhancing mechanisms: (1) an attenuation-region difference-driven subcarrier selection method, which filters subcarriers that reliably reflect the diffraction attenuation pattern by quantifying the signal contrast between diffraction- and reflection-dominated regions; and (2) an uncertainty evaluation framework that integrates result consistency and diffraction signal quality to eliminate unreliable estimates. Implemented entirely with commodity off-the-shelf (COTS) hardware, DiffLoc+ achieves an average angular error of 11.92° across six diverse indoor environments and eleven commercial camera models, demonstrating its effectiveness and robustness.

Presents reviews for the following list of books, Electromagnetic Radiation, Scattering, and Diffraction.

Electromagnetic diffraction and bidirectional plasmon launching in partially gated two-dimensional systems

Terahertz (THz) optical devices have emerged as critical tools across diverse applications, owing to the distinctive properties of THz radiation. The ability of THz waves to penetrate nonconductive materials enables numerous nondestructive testing applications, while their characteristic interaction with molecular vibrations produces unique spectral fingerprints, facilitating precise material identification and quantification. Moreover, the low photon energy of THz radiation makes it particularly suitable for biological inspection without sample damage. Despite these advantages, conventional THz devices, including emitters and detectors, remain bulky, impeding their miniaturization and integration. THz metalenses offer a promising solution by enabling wavefront control in compact, planar architectures. However, their reliance on electromagnetic diffraction introduces significant dispersion, presenting substantial challenges for implementation in the inherently broadband THz regime, which often spans multiple octaves. Herein, an advanced all‐dielectric metalens operating at dual‐frequency harmonics in the sub‐THz regime is demonstrated. The lens, fabricated using commercial 3D printing technology, enables rapid prototyping and cost‐effective manufacturing. This metalens achieves a numerical aperture of 0.86 (50 mm diameter, 15 mm focal length) at both 150 and 300 GHz. This development represents a significant advancement toward implementing higher‐order metasurface elements in the THz regime.

This study presents the first numerical solution to the 3D diffraction problem involving perfectly electric conducting (PEC) parallel circular double disks, excited by an arbitrarily polarized and located Hertzian dipole, using the Method of Auxiliary Sources (MAS). A comprehensive theoretical framework is established, and numerical simulations are conducted to analyze the frequency characteristics and field distributions of PEC double disks. The study investigates the effects of various parameters, such as disk radius, inter-disk distance, wavenumber, incident angle source location, and the dipole's position along the coordinate axes inside the disks, on the system's resonance behavior. The convergence of the MAS is thoroughly analyzed to ensure numerical reliability. These numerical results contribute valuable insights into the resonance characteristics of PEC double disks across various configurations. They serve as a guide for designing and optimizing resonators used in microwave and optical system applications.

This research introduces a novel experimental approach for identifying conductive and non-conductive objects submerged in shallow water using grounded cables. The methodology is underpinned by a comprehensive mathematical analysis of electromagnetic field diffraction caused by elongated conductive and non-conductive spheroids in an aqueous environment, specifically when interacting with a grounded cable. The experimental configuration employs a parallel arrangement of a generator and two receiving electrode antennas. A key feature of this technique is its ability to distinguish an object's unique flow characteristic from ambient noise. This is achieved through the application of digital hardware and software filtering to a modulated sinusoidal signal. To facilitate this process, the researchers developed a specialized algorithm designed to filter out pulse and fluctuation interference. This innovative approach represents a significant advancement in underwater object detection, offering potential applications in various fields such as marine archaeology, environmental monitoring, and underwater infrastructure inspection.

A general theory for solving electromagnetic diffraction problems with impenetrable/penetrable wedges immersed in/made of an arbitrary linear (bianistropic) medium is presented. This novel and general spectral theory handles complex scattering problems by using transverse equations for layered planar and angular structures, the characteristic Green function procedure, the Wiener–Hopf technique, and a new methodology for solving GWHEs. The technique has been proven effective for analyzing problems involving wedges immersed in isotropic media; in this study, we extend the theory to more general cases while providing all necessary mathematical tools and corresponding validations. We obtain generalized Wiener–Hopf equations (GWHEs) from spectral functional equations in angular regions filled by arbitrary linear media. The equations can be interpreted with a network formalism for a systematic view. We recall that spectral methods (such as the Sommerfeld–Malyuzhinets (SM) method, the Kontorovich–Lebedev (KL) transform method, and the Wiener–Hopf (WH) method) are well-consolidated, fundamental, and effective tools for the correct and precise analysis of electromagnetic diffraction problems constituted by abrupt discontinuities immersed in media with one propagation constant, although they are not immediately applicable to multiple-propagation-constant problems. To the best of our knowledge, the proposed mathematical technique is the first extension of spectral analysis to electromagnetic problems in the presence of angular regions filled by complex arbitrary linear media, thereby providing novel mathematical tools. Validation through fundamental examples is proposed.

In this paper, we revisit the classic problem of diffraction of electromagnetic waves by an aperture in a perfectly conducting plane. We formulate the diffraction problem using a boundary integral equation that is defined on the aperture using Dyadic Green’s function. This integral equation turns out to align with the one derived by Bethe using fictitious magnetic charges and currents. We then investigate the boundary integral equation using a saddle point formulation and establish the well-posedness of the boundary integral equation, including the existence and uniqueness of the solution in an appropriately defined Sobolev space.

Background. The present article investigates the reciprocal action of specific medium effects on electromagnetic waves propagation. The object of study is a moving dielectric, which at rest already demonstrate bianisotropic properties, i. e., it is a synthetic material, e. g., chiral media with Ω-particles. Bianisotropic material equations are the most general for describing the effects of electromagnetic waves interaction with complex medium. Studying and analyzing them is proving to be a notable scientific problem. Natural bianisotropy is a property of simple media under special conditions (state of motion, internal currents and diffusion processes), whereas artificial bianisotropy is an inherent property of the synthetic material itself (composite material, material with different metaparticles). Aim. The main goal of the work is to generalize the already available data. On it basis, then, obtain analytical expressions, which can be effectively used for the experiments designing, creating new computational techniques for solving direct and inverse electromagnetic diffraction problems. Methods. In this paper, analytical methods are applied to obtain the resulting close-form expressions. Results. Three classes of effects have been identified that have a significant reciprocal effect on each other: gyrotropy, spatial dispersion, and temporal dispersion. In this article it was shown that the gyrotropy of the medium has not only a simple additive effect, but under some, specific conditions, can be related to the system emergence. Conclusion. The reciprocal action of the spatial dispersion of the moving chiral medium, generally has different scales in range. Temporal dispersion was investigated, which does not have a simple additive property, because even an isotropic medium acquires fundamentally new material properties of bianisotropy when it moves.

A comparative study of efficient iterative solvers for the discrete dipole approximation

Tight focusing properties of azimuthally polarized Lorentz Gaussian vortex beam through a dielectric interface are numerically studied by vector diffraction theory. The focusing properties, such as spot size, depth of focus, and maximum intensity position, are numerically calculated by properly manipulating the Lorentz parameter with/without annular obstruction values. Thus, using annular obstruction, one can generate a highly confined focal spot of long focal depth when using an azimuthally polarized Lorentz Gaussian vortex beam. Full Text: PDF References A. Ashkin et al., "Observation of a single-beam gradient force optical trap for dielectric particles", Opt. Lett. 11, 288 (1986). CrossRef A. Ambardekar, Y.Q. Li, "Optical levitation and manipulation of stuck particles with pulsed optical tweezers", Opt. Lett. 30, 1797 (2005). CrossRef P. Zemánek, C.J. Foot, "Atomic dipole trap formed by blue detuned strong Gaussian standing wave", Opt. Commun. 146, 119(1998). CrossRef S.M. Block et al., "Bead movement by single kinesin molecules studied with optical tweezers", Nature 348, 348 (1990). CrossRef D.E. Smithet al., "The bacteriophage φ29 portal motor can package DNA against a large internal force", Nature 413, 748 (2001). CrossRef L. Oroszi et al., "Direct Measurement of Torque in an Optical Trap and Its Application to Double-Strand DNA", Phys. Rev. Lett. 97, 058301 (2006). CrossRef D.P. Biss, T.G. Brown, "Cylindrical vector beam focusing through a dielectric interface", Opt. Express 9, 490 (2001). CrossRef P. Török et al., "Electromagnetic diffraction of light focused through a planar interface between materials of mismatched refractive indices: structure of the electromagnetic field. I", J. Opt. Soc. Am. A 12, 2136 (1995). CrossRef S.H. Wiersma et al., "Comparison of different theories for focusing through a plane interface", J. Opt. Soc. Am. A 14, 1482 (1997). CrossRef L.E. Helseth, "Roles of polarization, phase and amplitude in solid immersion lens systems", Opt. Commun. 191, 161 (2001). CrossRef P. Zhou et al., "Propagation properties of a Lorentz beam array", Appl. Opt. 49, 2497 (2010). CrossRef O.E. Gawhary, S. Severini, "Lorentz beams and symmetry properties in paraxial optics", J. Opt. A: Pure Appl Opt 8, 409 (2006). CrossRef J. Yang et al., "Focusing of diode laser beams: a partially coherent Lorentz model", Proc. SPIE 6824, 68240 A (2007). CrossRef O.E. Gawhary, S. Severini, "Lorentz beams as a basis for a new class of rectangularly symmetric optical fields", Opt. Commun. 269, 274 (2007). CrossRef H. Yu, L. Xiong, B. Lü, "Nonparaxial Lorentz and Lorentz–Gauss beams", Optik 121,1455(2010). CrossRef Z. Zhang, J. Pu, X. Wang, "Tight Focusing of Radially and Azimuthally Polarized Vortex Beams through a Dielectric Interface", Chin. Phys. Lett. 25, 1664 (2008). CrossRef

Reconfigurable High-Efficiency metadevice using Kirigami-Inspired phase gradient metasurfaces

Probing material properties at surfaces down to the single-particle scale of atoms and molecules has been achieved, but high-resolution subsurface imaging remains a nanometrology challenge due to electromagnetic and acoustic dispersion and diffraction. The atomically sharp probe used in scanning probe microscopy (SPM) has broken these limits at surfaces. Subsurface imaging is possible under certain physical, chemical, electrical, and thermal gradients present in the material. Of all the SPM techniques, atomic force microscopy has entertained unique opportunities for nondestructive and label-free measurements. Here, we explore the physics of the subsurface imaging problem and the emerging solutions that offer exceptional potential for visualization. We discuss materials science, electronics, biology, polymer and composite sciences, and emerging quantum sensing and quantum bio-imaging applications. The perspectives and prospects of subsurface techniques are presented to stimulate further work toward enabling noninvasive high spatial and spectral resolution investigation of materials including meta- and quantum materials.

The study of the electromagnetic diffraction from penetrable screens with apertures and/or inhomogeneities is of great relevance today due to the huge number of modern applications in which they are involved. In this paper, the analysis of the plane wave scattering from a resistive-filled circular hole in a resistive plane is addressed. The uniquely solvable boundary value problem for the Maxwell equations, obtained via imposing generalized boundary conditions, power boundedness condition, and Silver–Muller radiation condition, is equivalently formulated in terms of an infinite set of singular dual integral equations in the vector Hankel transform domain. The Helmholtz–Galerkin technique allows for the discretization and, simultaneously, analytical regularization of the obtained integral equations. Fast convergence is guaranteed by a suitable choice of the basis functions reconstructing the physical behavior of the fields at the discontinuity between the two involved media. Moreover, the full-wave nature of the proposed approach allows the direct assessment of near-field and far-field parameters.

This study investigates several substantial questions arising in the diffraction by circular surfaces with the fractional boundary condition, which is the generalization of Dirichlet and Neumann boundary conditions.The study analyses the electromagnetic E-polarized plane wave diffraction by a slotted circular cylinder with the fractional boundary condition.For the first time, the fractional boundary condition regarding circular geometries is employed in the literature.The resonance characteristics for different boundary conditions, angle of incidence, and aperture sizes are analyzed.The new resonances are observed when the surface is different from the perfect electric or magnetic conducting surface.

Abstract In the present study, a new methodology in computational electromagnetics is developed for two-dimensional arbitrarily-shaped objects with impedance boundary conditions. The proposed approach investigates the E-polarized electromagnetic diffraction by a two-dimensional object with the Leontovich boundary condition. The scattered electric and magnetic fields are expressed as the convolution integral of the corresponding Green’s function and the current induced on the obstacle surface. After obtaining integral equations by applying the boundary condition, the integral equations are solved as in the case of the method of auxiliary sources (MAS) which is a well-known method in computational electrodynamics. The results are compared with first, different methods such as the method of moments (MoM), orthogonal polynomials (OP), and second, different boundary conditions such as Dirichlet, Neumann, and fractional boundary conditions. Some results are also obtained for the different shape scatterers at some values of the surface impedance.

There are many methods for rigorously calculating electromagnetic diffraction by objects of arbitrary shape and permittivity. In this article, we will detail the discrete dipole approximation (DDA) which belongs to the class of volume integral methods. Starting from Maxwell’s equations, we will first present the principle of DDA as well as its theoretical and numerical aspects. Then, we will discuss the many developments that this method has undergone over time and the numerous applications that have been developed to transform DDA in a very versatile method. We conclude with a discussion of the strengths and weaknesses of the DDA and a description of the freely available DDA-based electromagnetic diffraction codes.

The 2-D diffraction of a pulsed electromagnetic (EM) plane wave by a semi-infinite sheet with conductive and dielectric properties is analyzed analytically with the aid of the Wiener–Hopf technique and the Cagniard–DeHoop technique. Novel exact analytical expressions describing the time-domain (TD) EM field in the presence of the conductive half-plane are derived. Moreover, closed-form approximate TD expressions are arrived at via Koiter’s approximate method of factorization. Illustrative numerical examples are presented.