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A flexible, dual-broadband and polarization insensitive coding metasurface is proposed to manipulate electromagnetic (EM) scattering in microwave frequency band. The 1-bit coding units “0” and “1” are formed by the Pancharatnam-Berry (PB) phase based on the same-sized meta-atoms with different orientations. The layout of the coding metasurface is obtained through genetic algorithm (GA). The simulation results indicate that the proposed coding metasurface in this paper can achieve more than 10 dB radar cross section (RCS) reduction in the range of 9.26-12.87 and 14.84-19.35 GHz in the planar case, which is attributed to the reorientation of the reflected energies into different directions by optimizing the coding sequence. The diffuse scattering performance in the dual-wideband is well maintained while the coding metasurface is conformal on metallic cylinder with diverse curvature radii. Moreover, the scattering characteristics of conformal metasurfaces become better with the decrease of curvature radius under the case of the certain size of the flexible metasurface. A flexible coding metasurface prototype is prepared and measured. The experiment results coincide with the numerical simulation ones, demonstrating the outstanding capacity of RCS reduction. The proposed design has potential application value in the field of antenna and stealth of more complex objects.

Funding Information: This work was supported in part by Saab AB. The work of Mikko K. Leino was supported in part by the Walter Ahlstr?m Foundation, in part by the Jenny and Antti Wihuri Foundation, and in part by the Nokia Foundation. Publisher Copyright: © 1963-2012 IEEE. A periodically loaded, low-scattering dipole suitable for the secondary surveillance radar, particularly for identification-friend-or-foe antenna, is presented along with the methods to design such an antenna. The dipole is chopped into the pieces with length that minimizes scattering at 10 GHz, i.e., at the operation frequency of the primary antenna. In addition, optimal inductive loading is found to connect the pieces together so that the formed entity can radiate at 1 GHz, i.e., at the operation of frequency of the secondary antenna. Two meander-line designs are presented to realize the required inductances, and the proposed structures are realized on a printed circuit board. Designed prototypes are analyzed through simulations and measurements, which are in good agreement. The reduction in radar cross section at 10 GHz with the inductively loaded dipoles is at best more than 15 dB, when compared to the reference half-wave dipole. As a consequence, the radiation efficiency at 1 GHz decreases by 0.4 dB withthe inductively loaded dipoles.

In this paper, we consider the propagation of waves in an open waveguide in ℝ$^{2}$ where the index of refraction is a local perturbation of a function which is periodic along the axis of the waveguide (which we choose to be the x$_{1}$ axis) and equal to one for |x$_{2}$| > h$_{0}$ for some h$_{0}$ > 0. Motivated by the limiting absorption principle (proven in an earlier paper by the author), we formulate a radiation condition which allows the existence of propagating modes and prove uniqueness, existence, and stability of a solution under the assumption that no bound states exist. In the second part, we determine the order of decay of the radiating part of the solution in the direction of the layer and in the direction orthogonal to it. Finally, we show that it satisfies the classical Sommerfeld radiation condition and allows the definition of a far field pattern.

Near-field radar cross-section (NF-RCS) of a target depends on antennas’ radiation and can be maximized by adjusting the radiation patterns. It is justified by the power return ratio and can be computed by a comparison method. A theoretical foundation of operational mechanism for phased arrays of antennas is presented to produce conformal radiations for NF-RCS enhancement. The target’s scattering coefficients are extracted from operating the antenna array’s digital phase shifters to steer the resulting beams in this work. The scattering matrix is then analyzed by the singular value decomposition (SVD) to determine the antennas’ excitations for maximum NF-RCS with estimation stability. It results in orthogonal beams for the two-way radiations of antenna arrays to interpret the scattering mechanisms. The feasibility is validated by HFSS full-wave simulations and experimental measurement data.

In turbid water, target reflected lidar signal is easily buried in “clutter” due to scattering. We proposed an underwater laser ranging model applying an optical vortex in the receiver to separate the scattering clutter from the target reflected signal. A spiral phase plate (SPP) was placed in front of the detector to convert the target reflected Gaussian beam to an optical vortex. While the scattering clutters were not able to be converted due to the loss of spatial coherence. Therefore, the target reflected signal and scattering clutters were spatially separated by the SPP. An underwater laser detection simulation using Zemax software was carried out. The numerical simulation showed that when the SPP was placed in front of the receiver, the contrast of signal to clutter of the detection was improved by blocking the scattering clutters which had a Gaussian distribution at the center on the detection plane. The effects of beam divergence and orbital angular momentum (OAM) order to the lidar performance were also analyzed.

In this article, a hypersonic target electromagnetic (EM) scattering echo model combined with the inhomogeneous zonal medium model (IZMM) and the classical scattering center model (SCM) is proposed with a distributed satelliteborne array radar as the detection platform. A parallel physical optics (PO) method is used for multiview inverse synthetic aperture radar (ISAR) imaging of a moving hypersonic target covered with plasma sheath based on the analysis of high-resolution range profile in the S-X ultrawideband range, reconstructing 2-D EM scattering echo data (the target) and motion compensation. The results show that the surface of the inhomogeneous plasma sheath flow field is an excitation layer with random and irregular fluctuation characteristics, which increases the false scattering centroid of the 1-D range profile of the hypersonic target and can interfere with and disrupt the radar localization of the target along the radial direction. In addition, shallow scattering of EM waves occurs in the plasma sheath, and the average signal intensity of the target can gradually reduce from 0.5 x 10⁻⁵ at 60 km and 20 Ma to 0.1 x 10⁻⁵ at 30 km and 20 Ma, with a fivefold weakening of the overall scattered echo signal. In particular, the faster the hypersonic target travels at 30-km altitude, the weaker the imaged scattered echo signal becomes, with the average intensity of the imaged signal weakening by approximately threefold from 15 to 25 Ma. This study provides considerable technical support and data assurance to establish a synthetic aperture radar (SAR) automatic target recognition (ATR) database, and the findings of this study can be used as a reference for fine-structure feature analysis of hypersonic targets for feature extraction and the classification and identification of targets.

For the traditional subwavelength gratings, we can code different units to construct the coded metagratings. In this paper, we propose an innovative principle of adding coded gratings, which can be used to add or subtract two or more traditional coded metagratings sequences and obtain a new coded metagratings sequence. Based on the proposed addition principle, the coded metagratings can adjust the scattering angle flexibly. This method overcomes the limitation that traditional grating can only obtain discrete diffraction angle. Importantly, compared with traditional gratings, the coded metagrating sequences with addition operation have enhanced diffraction efficiency at the same diffraction angle. This phenomenon may be attributed to the enhanced interaction between the coding particles of the new disordered coding sequence metagratings constructed. Our proposed coded grating addition principle provides a new degree of freedom for the flexible modulation of the terahertz wavefront. At the same time, this method can be extended to optical band or microwave band, which opens a new path for electromagnetic wave modulation and beam scanning.

A dual-polarized lower-band (LB) antenna element is proposed in this paper. A pair of vertical arms and a pair of horizontal arms are designed with two cross -shaped feeding lines together for 45polarizations. The sleeve arm can suppress the scattering for high frequency electromagnetic wave, and have almost negligible effect on low frequency. Meanwhile, unobstructed space for placing the higher-band (HB) elements is reserved with surrounded scheme. The dual-band antenna (DBA) with four HB elements operating from 1.46~2.43 GHz and one LB element operating from 0.65~1.11 GHz is designed and fabricated. The simulated and measured results show that stable radiation performance and low mutual interference for LB and HB elements are achieved in DBA.

Electromagnetic wave scattering suppression has applications in many scenes including radio communication and electromagnetic compatibility. A large amount of research focus on absorber structures with reflection suppression at -10 dB level, while scattering suppression beyond -10dB level is rather rare. In order to study the formation of higher suppression, metamaterial with absorption and scattering composite function is presented based on coding sequence of absorptive electromagnetic genetic components. Quantized experimental measurement result of scattering suppression reaches -22.4 dB in consecutive 7.152 GHz - 16.184 GHz band (relative bandwidth 77.4%), which shows consistent trend with simulation and validates the design process. Optimization with small gene coding variation rate (4.7%) makes scattering suppression effect surpass -30 dB line in 9.45 GHz - 13.8 GHz in simulation. Besides camouflage function, this metamaterial could alter the scattering information in spatial distribution with high suppression effect, which has a good chance to serve as transmitter in local area network with good privacy.

A method to suppress cross-band scattering is presented in this letter. A two-antenna system is analyzed, which consists of a lower-band (LB) dipole and a higher-band (HB) dipole. A pair of sleeves is loaded on the arms of the LB dipole. The cross-band scattering between the HB and LB antennas close to each other usually deteriorates the pattern of the HB antenna. In the proposed antenna system, the sleeves loaded on the arms of the LB dipole are used to suppress the induced current on the LB antenna and reduce the cross-band scattering in the two-dipole system, which restores the radiation pattern of the HB antenna. A prototype of the proposed antenna system is fabricated and measured. The results show that the maximum radiation direction of the HB antenna is changed from a maximum of 24 degrees back to 0 degrees in H-plane.

This communication presents a low-profile and low scattering wideband planar phased antenna array with enhanced coupling (PAA-EC). The proposed chessboard-like PAA-EC consists of two different types of low-profile planar antenna elements that have similar radiation performance in the X-band. In addition, the two types of antenna elements have a 180° ± 37° reflection phase difference over the X-band, which guarantees the cancelation of scattering fields for low scattering purpose. On the other hand, an 8×8 reference PAA-EC and a low scattering PAA-EC are developed and fabricated to validate the radiation performance and scattering characteristics. The simulated and measured results show that the proposed low-profile planar PAA-EC operates in the 8-12 GHz band with ±45° scanning range. It also achieves at least 9-dB scattering cross section (SCS) reduction in the 8-15.2 GHz band as compared with the reference PAA-EC.

A filtering transmitarray antenna (TAA) with high-gain in-band radiations at the $X$ -band and an out-of-band low-scattering characteristic is presented in this communication. The proposed composite TAA element consists of a dual-polarized resistive sheet, a fixed bandstop frequency-selective surface (FSS) element, and an adjustable bandpass FSS element also serving as a phase shifter. The resistive element is constructed by inserting a parallel inductor–capacitor (PLC) resonant structure into the center of a lumped-resistor-loaded metallic dipole. A transparent frequency-domain window at the center operating frequency ( $f_{c}$ ) is created by the PLC resonance and is further shared by both FSS elements, hence allowing for high in-band transmission herein. At frequencies below or above $f_{c}$ , the whole composite TAA element acts as an absorber with the bandpass or bandstop FSS elements as the ground planes for the resistive sheet, respectively. The measured results show that the composite TAA can achieve gain-filtering responses with out-of-band suppression levels ≥25 dB, ~8 dB scattering cross section (SCS) reductions in 4–7 and 14–20 GHz, and the radiation gain of 25.3 dBi simultaneously. Because of these merits, the proposed design can relieve the stress on filtering circuit designs, also offering an attractive solution in stealth technology.

The complex-source (CS) method in conjunction with the spherical-multipole analysis is used to explore and demonstrate the different local phenomena associated with beam-wave scattering by acoustically hard or soft circular cones. The illumination by a beam allows a selective excitation of the scattering phenomena which include reflections, tip diffraction, and creeping beam-waves, where all of them coalesce in the vicinity of the tip. These phenomena depend on the beam’s direction and width, on whether the incident beam is converging or diverging as it hits the scatterer, and on whether the scattering point is within or beyond the beam collimation zone. A generalization of the CS method is introduced that can address converging beams. Special emphasis is given to identifying and explaining the footprint of the local diffraction phenomena. All the numerical details are provided so that the reader can readily explore the problem further. For interested readers, supplementary videos are available on IEEE DataPort that give further insight into wave physics and clarify the direction of wave propagation.

The two-photon fluorescence imaging depth has been significantly improved in recent years by compensating for tissue scattering with wavefront correction. However, in most approaches the wavefront corrections are valid only over a small sample region on the order of 1 to 10 µm. In samples where most scattering structures are confined to a single plane, sample conjugate correction geometries can increase the observable field to a few tens of µm. Here, we apply a recently introduced fast converging scheme for sensor-less scattering correction termed “Dynamic Adaptive Scattering compensation Holography” (DASH) in a sample conjugate configuration with a high pixel count nematic liquid crystal spatial light modulator (LC-SLM). Using a large SLM allows us to simultaneously correct for scattering at multiple field points, which can be distributed over the entire field of view provided by the objective lens. Despite the comparably slow refresh time of LC-SLMs, we achieve correction times on the order of 10 s per field point, which we show is sufficiently fast to counteract scattering at multiple sites in living mouse hippocampal tissue slices.

The discovery and development of ultra-wide bandgap (UWBG) semiconductors is crucial to accelerate the adoption of renewable power sources. This necessitates an UWBG semiconductor that exhibits robust doping with high carrier mobility over a wide range of carrier concentrations. Here we demonstrate that epitaxial thin films of the perovskite oxide NdxSr1−xSnO3 (SSO) do exactly this. Nd is used as a donor to successfully modulate the carrier concentration over nearly two orders of magnitude, from 3.7 × 1018 cm−3 to 2.0 × 1020 cm−3. Despite being grown on lattice-mismatched substrates and thus having relatively high structural disorder, SSO films exhibited the highest room-temperature mobility, ~70 cm2 V−1 s−1, among all known UWBG semiconductors in the range of carrier concentrations studied. The phonon-limited mobility is calculated from first principles and supplemented with a model to treat ionized impurity and Kondo scattering. This produces excellent agreement with experiment over a wide range of temperatures and carrier concentrations, and predicts the room-temperature phonon-limited mobility to be 76–99 cm2 V−1 s−1 depending on carrier concentration. This work establishes a perovskite oxide as an emerging UWBG semiconductor candidate with potential for applications in power electronics.

Introduction. Computer-aided design systems for microwave devices are an effective tool for assessing the backscattering characteristics of complex-shaped objects. However, these calculations are often associated with significant computational costs, especially at large values of the ratio of the characteristic dimensions of the object to the wavelength. The use of asymptotic methods in combination with the mesh coarsening of object partition can significantly reduce these costs. However, in each practical case, this leads to a deterioration in the accuracy of the estimates obtained, which is hard to predict.Aim. Comparative assessment of the results of modeling the scattering field in the CAD of microwave devices using various methods for calculating and detailing the object model in the decimeter and centimeter wavelength ranges.Materials and methods. The research object was an anti-tank guided missile FGM-148 Javelin. The scattering field of Altair FEKO microwave devices was modeled in CAD using the methods of moments and physical optics in the frequency range from 1 to 10 GHz and angles from 0 to 180°. A comparison of one-dimensional backscatter diagrams and radar images obtained using these methods was carried out.Results. For the class of objects under consideration, the method of physical optics provides acceptable accuracy at frequencies of 5 GHz and higher with a step of partitioning the model surface of the order of one centimeter and a total calculation duration of the order of several minutes (Intel Core i5-4460 PC / 3.2 GHz / 8 MB RAM). At lower frequencies, acceptable accuracy and a similar calculation duration are achieved when calculating by the method of moments and a partitioning step of about 20 cm. The possibility of using the Altair FEKO CAD system for modeling radar images of objects with a resolution of at least 20 cm is demonstrated.Conclusion. The results obtained complement the well-known studies in the field of comparative assessment of the time and accuracy characteristics of various methods for calculating the scattering field of objects in the CAD of microwave devices.

The coherence properties of the beam provided at the CoSAXS beamline at the MAX IV Laboratory are determined experimentally using multi-mode ptychography. The coherent fraction of the beam is then used for a proof-of-concept XPCS measurement, illustrating the beamline’s capabilities., The CoSAXS beamline at the MAX IV Laboratory is a modern multi-purpose (coherent) small-angle X-ray scattering (CoSAXS) instrument, designed to provide intense and optionally coherent illumination at the sample position, enabling coherent imaging and speckle contrast techniques. X-ray tracing simulations used to design the beamline optics have predicted a total photon flux of 1012–1013 photons s−1 and a degree of coherence of up to 10% at 7.1 keV. The normalized degree of coherence and the coherent flux of this instrument were experimentally determined using the separability of a ptychographic reconstruction into multiple mutually incoherent modes and thus the Coherence in the name CoSAXS was verified. How the beamline can be used both for coherent imaging and XPCS measurements, which both heavily rely on the degree of coherence of the beam, was demonstrated. These results are the first experimental quantification of coherence properties in a SAXS instrument at a fourth-generation synchrotron light source.

Understanding lattice dynamics is crucial for effective thermal management in electronic devices because phonons dominate thermal transport in most semiconductors. α-GaN has become a focus of interest as one of the most important third-generation power semiconductors, however, the knowledge on its phonon dynamics remains limited. Here we show a Matryoshka phonon dispersion of α-GaN with the complementary inelastic X-ray and neutron scattering techniques and the first-principles calculations. Such Matryoshka twinning throughout the basal plane of the reciprocal space is demonstrated to amplify the anharmonicity of the related phonons through creating abundant three-phonon scattering channels and cutting the lifetime of affected modes by more than 50%. Such phonon topology contributes to reducing the in-plane thermal transport, thus the anisotropic thermal conductivity of α-GaN. The results not only have implications for engineering the thermal performance of α-GaN, but also offer valuable insights on the role of anomalous phonon topology in thermal transport of other technically semiconductors. Lattice dynamics can govern the thermal conductivity solids and understanding the underlying mechanisms may enable enhanced performance of devices via judicious engineering. Here, insight into the anisotropic thermal conductivity of semiconducting α-GaN is gained by measuring the Matryoshka phonon dispersions.

Plasmonic gold nanorods (GNRs) are finding increasing use in biomedicine due to their unique electromagnetic properties, optical contrast enhancement and biocompatibility; they also show promise as polarization contrast agents. However, quantification of their polarization-enhancing properties within heterogeneous turbid media remains challenging. We report on polarization response in controlled tissue phantoms consisting of dielectric microsphere scatterers with varying admixtures of GRNs. Experimental Mueller matrix measurements and polarization sensitive Monte-Carlo simulations show excellent agreement. Despite the GNRs’ 3D random orientation and distribution in the strong multiply scattering background, significant linear diattenuation and retardance were observed. These exclusive measurable characteristics of GNRs suggest their potential uses as contrast enhancers for polarimetric assessment of turbid biological tissue.

In this article, we propose a software–hardware system to improve the quality of image recovery in millimeter-wave (MMW) imaging systems, which aims to benefit from copolarization and cross-polarization scatterings from the target. The proposed dual-polarized antenna array structures consist of two orthogonal subarrays with the same phase center, where each subarray is comprised of $2\times 1$ or $4\times 1$ rectangular edge fed patches and the optimized ground defects. These compact structures, which support radiation of two orthogonal linear polarizations, are designed on a single-layer board using crossover technique. The dual-polarized scattering from the target is captured by the orthogonal subarrays. Furthermore, we introduce a method to combine data obtained from measured dual (co- and cross-) polarized fields to improve the recovery of edge information and increase image quality. The proposed single-layer designs have been fabricated and measured, which exhibits high port isolation and high polarization purity. The cross-polarization level is at least 22 and 25 dB lower than the copolarization pattern for $2\times 1$ and $4\times 1$ arrays, respectively. The measured 10 dB impedance bandwidth of the $2 \times 1$ and $4\times 1$ subarrays ranges from 27 to 29.3 GHz and from 27 to 29.5 GHz, respectively. Moreover, the radiation gains of the $2 \times 1$ and $4\times 1$ subarrays are 9.7 and 12 dBi, respectively. The simulated and measured imaging results show that the cross-polarized data preserve the edge information. Moreover, by using the proposed data combination technique, the quality of the recovered image is improved.

Soft protons are a potential threat for X-ray missions using grazing incidence optics, as once focused onto the detectors they can contribute to increase the background and possibly induce radiation damage as well. The assessment of these undesired effects is especially relevant for the future ESA X-ray mission Athena, due to its large collecting area. To prevent degradation of the instrumental performance, which ultimately could compromise some of the scientific goals of the mission, the adoption of ad-hoc magnetic diverters is envisaged. Dedicated laboratory measurements are fundamental to understand the mechanisms of proton forward scattering, validate the application of the existing physical models to the Athena case and support the design of the diverters. In this paper we report on scattering efficiency measurements of soft protons impinging at grazing incidence onto a Silicon Pore Optics sample, conducted in the framework of the EXACRAD project. Measurements were taken at two different energies, ~470 keV and ~170 keV, and at four different scattering angles between 0.6 deg and 1.2 deg. The results are generally consistent with previous measurements conducted on eROSITA mirror samples, and as expected the peak of the scattering efficiency is found around the angle of specular reflection., 16 pages, 11 figures; accepted for publication on Experimental Astronomy

International audience; Evanescent-wave scattering is a topic in classical electrodynamics and in the study of colloidal particles near a boundary. However, how such near-surface scattering at subcellular refractive-index heterogeneities degrades the excitation confinement in biological total internal reflection fluorescence microscopy has not been well studied. An elegant theoretical work by Axelrod and Axelrod now addresses this very relevant question and reveals that-even when scattered-evanescent light preserves some of its surprising optical properties.

The modification of a conventional plasma window antenna (PWA) into a novel endfire plasma array antenna (E-PAA) and the comparison of their performances are first made. It will be shown that the E-PAA provides better performance than the PWA does. Then, the gain improvement and more importantly the radar cross section (RCS) reductions for stealth properties of the E-PAA are described. A type of feeding and generating system of plasma antenna is given. Simulated and measured results at 300 MHz are discussed, indicating the potential applications of the E-PAA in high-level integrating of radio transceivers onboard for wireless communications.

The hyperbolic phonon polaritons supported in hexagonal boron nitride (hBN) with long scattering lifetimes are advantageous for applications such as super-resolution imaging via hyperlensing. Yet, hyperlens imaging is challenging for distinguishing individual and closely spaced objects and for correlating the complicated hyperlens fields with the structure of an unknown object underneath. Here, we make significant strides to overcome each of these challenges. First, we demonstrate that monoisotopic h11BN provides significant improvements in spatial resolution, experimentally resolving structures as small as 44 nm and those with sub 25 nm spacings at 6.76 μm free-space wavelength. We also present an image reconstruction algorithm that provides a structurally accurate, visual representation of the embedded objects from the complex hyperlens field. Further, we offer additional insights into optimizing hyperlens performance on the basis of material properties, with an eye toward realizing far-field imaging modalities. Thus, our results significantly advance label-free, high-resolution, spectrally selective hyperlens imaging and image reconstruction methodologies.

Surface plasmon polariton (SPP) waves are the most extensively studied waves among various types of surface waves because they are easy to excite and have been used in many optical applications particularly for plasmonic communication, sensing, and harvesting solar energy. In all these applications, especially on-chip plasmonic communication, scattering can be an important issue to deal with. Therefore, this paper aimed to theoretically inspect the scattering pattern of SPP waves from a perfect electric conductor (PEC) cylindrical scatterer. The cylindrical wave approach is used to solve the scattering problem by a cylindrical object placed below a metallic layer. The scattering is investigated thoroughly by changing the size of the scatterer and its distance from the interface along which the SPP wave is excited. As the size of the scatterer increases, the scattering increases significantly. On the other hand, when the distance of the scatterer from the interface is increased, the scattered field becomes small. Two-dimensional field maps are produced for the incident angle at which SPP is excited. Numerical results are also presented for other incident angles to make a comparison. Furthermore, the forward and backward far-fields are significantly enhanced if the SPP wave is scattered in comparison with when the SPP wave is not present.

Asymptotic solutions based on the uniform geometrical theory of diffraction (UTD) are well developed and efficient for analyzing radiation, mutual coupling, and scattering associated with electrically large conducting convex surfaces. Relevant UTD solutions are available mostly for infinitesimal sources on or far away from the surface. Hence, UTD solutions have been extensively used to analyze radiation from conformal antennas and antenna arrays on an electrically large convex surface. In this letter, it is proposed to predict far and near field radiations from a monopole antenna array on an electrically large conducting convex surface as a nonconformal array. A UTD solution that allows sources to be on or slightly off the surface is employed after identifying ray paths. UTD results are validated with those of the multilevel fast multipole method.

As an object is passing through a static scattering medium, a speckle is formed. We can reconstruct the image from the speckle, based on the principle of optical memory effect. However, when the object passes through a dynamic scattering medium, such as fog, the reconstructed image quality will be degraded even blurred. In this paper, we want to investigate the reconstructed image as the object passes through the dynamic scattering medium, which is simulated by a rotating ground glass. We focus on studying the influence of both the acquisition time of the CCD and the angular velocity of the rotating ground glass on the fidelity of the reconstructed image. The experimental results show that appropriately reducing the acquisition time of the CCD is beneficial to reconstruct image from the single speckle in the dynamic scattering imaging. The proposed results may have applications in imaging through fog and biological tissues.

In this paper, a new robust computational method that applies the geometrical theory of diffraction (GTD) in conjunction with the ray tracing (RT) technique is developed to evaluate the electromagnetic scattering pattern due to a plane wave represented as beam of parallel rays incident on a rough surface of quite arbitrary statistical parameters. The development of the proposed technique is explained in detail taking into consideration the generation of the geometrical model of the rough surface. The Fresnel reflection model is applied under the assumption of arbitrary electrical and optical properties of the rough surface material. Also the polarization of the plane wave primarily incident on the rough surface is taken into consideration. The algorithm developed in the present work accounts for multiple bounces of an incident ray and, hence, it can be considered arbitrary higher-order GTD-RT technique. The accuracy of the obtained results is verified through the comparison with the experimental measurements of the scattering pattern of a light beam incident on rough sheets with specific statistical properties. The numerical results of the present work are concerned with investigating the dependence of the scattering pattern on the surface roughness, refractive index, angle of incidence, and the resolution of the geometric model of the rough surface. Also, it is shown that, for limited resolution of the rough surface model, the accuracy of the calculated scattered field depends on the angle of incidence of the primary beam and the surface roughness.

A conducting deep cavity is an essentially geometric structure, e.g., the inlet duct and the tail nozzle, of air vehicles and is a dominant scattering source of radar echoes. The scattering centers (SCs) induced by multiple reflections inside deep cavities are different from general SCs. Few references have studied the SC model for deep cavities. Therefore, a concise SC model is presented in this letter. In this model, an analytical expression for the projection distances of SCs along the line-of-sight (LOS) in deep cavities is derived by using the ray- tracing method. Rectangular cavities, cylindrical cavities, and a cavity composed of two cylindrical structures are investigated in this letter. The presented SC models are validated by a comparison between the radar images simulated by the model and those computed by a full-wave numerical method.

In optical sensing, the differentiation between absorption and scattering poses a challenge when dealing with a physiological medium. We have shown that for extracting absorption-based parameters it is optimal to measure at the iso-path length (IPL) point. The IPL position is dependent on the diameter of the medium. In this paper, we will demonstrate how beam shaping can help match the light pattern, so the IPL point remains in the same position and distance from the light source. Hence, the location of the detector will remain constant for different mediums, such as different fingers. A spatial frequency of 0.4 mm−1, in the case of a 15mm diameter cylindrical phantoms, shifts the IPL point's position by 40 degrees on the phantom's surface. Moreover, the spatial modulation yields an optical signature from different depths, which could improve the extraction of optical properties from tissue depth using our method.

A method to suppress cross frequency band scattering in multiband array (MBA) is proposed in this letter. Due to the short distance between the lower band (LB) elements and the higher band (HB) elements in MBA, the performances of the elements are distorted. By adding three L-shaped branches to each arm of LB element, the induced current can be effectively regulated, which greatly reduces the cross-band scattering ability of the array. Thus, the elements of each frequency band do not interfere with each other and work alone. This method is applied to the MBA with the interleaved scheme, which consists of one LB element with the operating frequency ranging from 0.73 to 0.86 GHz, and four HB elements with the operating frequency ranging from 1.79 to 2.41 GHz. Both simulation and measurement of proposed geometry show that this method is simple, effective, and easy to fabricate. The proposed geometry can be widely used in multiple wireless communication systems due to its high isolation, stable radiation patterns, and lower cross-band scattering.

A rigorous theory is developed for the multiple scattering analysis of an E− polarised plane wave from an ensemble of 2‐D slotted arbitrary cylinders. The Method of Analytical Regularisation, previously applied to the solution of scattering wave problems for isolated slotted cylinders, is generalised to problems incorporating ensembles of closed or slotted cylinders. Numerical calculations of the complex eigenvalues, Q− factors and resonant current densities are performed for various configurations of two slotted circular or elliptical cavities, focussing on an accurate assessment of differing peculiarities of the mutual resonant electromagnetic coupling.

Optical couplers play an important role in optical switches to split or combine light power in a predictable way. We proposed a novel scheme of photonic crystal (PhC) couplers relying on the unique characteristics of band-edge resonance. Stretched fundamental resonance can be excited in a square array of several periods to realize efficient transverse scattering. Two types of 1 × 2 and 2 × 1 PhC-couplers have been designed. The iconic features of ultra-compact constructure, ideal 3 dB splitting, and constant phase shift of 0/π prove the PhC-couplers are appropriate for splitters, combiners, and optical switches. Both numerical and experimental results validate that this PhC-coupling optical switch exhibits significant switching performances over a large variation of structural parameters. This work will be of interest for the development of optical components integration in micro-nano photonic circuits and related applications. Two types of 1 × 2 and 2 × 1 photonic crystal couplers have been proposed relying on stretched fundamental resonance near the photonic band edge. The iconic features of ultra-compact structure, ideal 3 dB splitting, and constant phase shift prove they are appropriate for the designs of splitters, combiners, and optical switches in optical components integration.

Recent years have witnessed a much broader use of Brillouin inelastic light-scattering spectroscopy for the investigation of phonons and magnons in novel materials, nanostructures and devices. Driven by the developments in instrumentation and the strong need for accurate knowledge on the energies of elemental excitations, Brillouin–Mandelstam spectroscopy is rapidly becoming an essential technique that is complementary to Raman inelastic light-scattering spectroscopy. We provide an overview of recent progress in the Brillouin light-scattering technique, focusing on the use of this photonic method for the investigation of confined acoustic phonons, phononic metamaterials and magnon propagation and scattering. This Review emphasizes the emerging applications of Brillouin–Mandelstam spectroscopy for phonon-engineered structures and spintronic devices, and concludes with a perspective on future directions. Nearly 100 years after the prediction of Brillouin light-scattering spectroscopy, or Brillouin–Mandelstam light-scattering spectroscopy, the effect has proved itself a powerful tool for decades. Now its application to probing confined acoustic phonons, phononic metamaterials and magnons is reviewed.

—The problem of scattering on an ideally conducting infinite cylinder of a monopolar electromagnetic pulse, the electric field of which is parallel to the cylinder axis, is considered by the methods of a computational experiment. It is shown that, regardless of the ratio of the spatial pulse length to the cylinder diameter, the scattered field is monopolar.

In this letter, a small target detection method in sea clutter background is proposed based on multiview polarization features and localized one-class support vector machine (LOCSVM). In the proposed method, three views of features that represent the divergence between the small target and the clutter are extracted: 1) the study of the target scattering characteristics shows that the dominant scattering components of the small target cell (TC) are sphere scattering and diplane scattering, while the scattering mechanism of the clutter cell is varied and affected by the sea conditions. Therefore, the relative powers of the sphere and diplane scattering components are extracted based on the polarimetric scattering matrix; 2) Because the target is a definite shaped object, its cell does not exist in the fractal characteristics, while the clutter cell is on the contrary. Therefore, the average Tsallis entropy (TE) is extracted from full-polarization channels to reflect the fractal characteristics of the cell; and 3) As the generalization of the Doppler entropy, because the frequency spectrum of the TC is more congregate, the TE can reflect the Doppler characteristics. Then, in the detection stage, a novel one-class classifier, referred to as LOCSVM, is designed as the detector. LOCSVM is a combination of $k$ -means clustering and OCSVM and can enhance the detection performance of OCSVM. The experimental results on the IPIX data show the effectiveness of the proposed method, especially in the case of short observation time.

Absorption spectroscopy is widely used to detect samples with spectral specificity. Here, we propose and demonstrate a method for enhancing the sensitivity of absorption spectroscopy. Exploiting multiple light scattering generated by a boron nitride (h-BN) scattering cavity, the optical path lengths of light inside a diffusive reflective cavity are significantly increased, resulting in more than ten times enhancement of sensitivity in absorption spectroscopy. We demonstrate highly sensitive spectral measurements of low concentrations of malachite green and crystal violet aqueous solutions. Because this method only requires the addition of a scattering cavity to existing absorption spectroscopy, it is expected to enable immediate and widespread applications in various fields, from analytical chemistry to environmental sciences.

In this chapter, neutron experimental techniques are described. The chapter covers the basics of neutron scattering, neutron source characteristics, diffraction techniques, inelastic neutron scattering, instruments for semi-macroscopic structure analysis, detectors, optics, choppers, and some concepts for instrument design. Techniques for both steady and pulsed sources are described, with more emphasis on the latter in view of the recent worldwide trend toward pulsed sources, generally pulsed spallation sources. The source character, even within the class of pulsed sources, has a significant influence on instrument design. Inelasticity effects in the total scattering technique are clearly specified in the chapter. Some details of chopper instruments, including resolution effects, are described, since this class of instruments has recently received considerable innovative development and use over a wide range of science. Recent developments in scintillation detectors are discussed as an alternative technology to more conventional 3He detectors. Optical components are becoming more and more important not only for neutron transport but also for background reduction. Neutron spin-echo techniques are presented as an example of the exploitation of polarized neutrons.

The ability to register and analyze the spatial distribution of light scattered within the full solid angle is the basis for the development and improvement of information-measuring systems and software and hardware complexes for problems of optical biomedical diagnostics. The greatest contribution to light scattering at non-invasive methods of biomedical research are made by the layers of human skin, affecting the depth of probing and the resolution of diagnostic systems. The significant individual variability of the optical properties of biological tissues does not allow practically (clinically) assessing their effect on the light scattering characteristics; therefore, the use of methods for modeling the optical radiation propagation in media in the measuring tools functioning context makes it possible to provide such a prognostic analysis. The goal of this work is a comparative evaluation of the results of the light propagation in human skin layers by Monte Carlo simulation using information-measuring systems of a biomedical photometer with ellipsoidal reflectors and a goniophotometer. The Monte Carlo simulation results of light scattering in dermis and epidermis at a wavelength of 632.8 nm using spatial photometry methods and the "BT_Mod" software, as well as coordinates, direction, and statistical weight of photons, allows the ray-tracing in a biomedical photometer with ellipsoidal reflectors are presented in this work. As a result of modeling, graphs of the dependence of optical coefficients (transmission T, diffuse reflection Rd, and absorption A) for the studied tissues of various thicknesses on the value of the scattering anisotropy factor were obtained, as well as photometric images of the second focal plane of ellipsoidal reflectors when receiving a scattering spot in reflected and transmitted light. Diagrams of the averaged scattering indicatrix at three thicknesses of the epidermis and dermis were obtained for a set of biophysically significant values of the scattering anisotropy factor, based on which the integral distribution of the photons statistical weight in diffuse scattered light was analyzed. A quantitative assessment of the illuminance level of images is carried out according to the zone analysis principles in photometry by ellipsoidal reflectors. The resulting graphs of the illuminance dependence the external and middle rings of photometric images in reflected and transmitted light. The results of the research make it possible to analyze the spatial distribution of light scattered by the human skin layers (epidermis and dermis) within the full solid angle, which can be used in problems of optical dosimetry and medical imaging in diagnostic, endoscopic, and therapeutic methods of biophotonics.

The human cell nucleus serves as an important organelle holding the genetic blueprint for life. In this work, X-ray ptychography was applied to assess the masses of human cell nuclei using its unique phase shift information. Measurements were carried out at the I13-1 beamline at the Diamond Light Source that has extremely large transverse coherence properties. The ptychographic diffractive imaging approach allowed imaging of large structures that gave quantitative measurements of the phase shift in 2D projections. In this paper a modified ptychography algorithm that improves the quality of the reconstruction for weak scattering samples is presented. The application of this approach to calculate the mass of several human nuclei is also demonstrated.

Design, realization, and measurements of an $X$ -band antenna for data downlink (DDL) from low Earth orbit (LEO) satellites are presented. This antenna has an isoflux radiation pattern and operates in dual circular polarization with cross-polar discrimination (XPD) higher than 18 dB on the operational bandwidth. Two solutions are first proposed: one realized by a metasurface with circular strips printed on a dielectric slab and another realized by concentric metallic corrugations. Starting from a basic scattering mechanism of a self-complementary ring-type metasurface excited by a perfectly polarized source, both these antennas are designed by optimizing an equivalent anisotropic impedance surface excited by a short hat feed. The corrugated antenna is realized and measured, confirming that the performances are compliant with the requirements for next-generation DDL antennas.

In this letter, the scattering of a nondiffractive Bessel beam (BB) incident field by a perfect electric conducting circular cylinder is investigated and compared with the standard scattering solution by a plane wave. It is proven that the BB incident field improves the validity of standard physical optics approximation and possibly extends its range of applicability to cylinders, or more general scatterers, whose curvature radius is not much larger than the operating wavelength. This offers new effective possibilities in the solutions of different electromagnetic scattering problems.

Cosmic-ray muon imaging is a kind of nondestructive detection technology which can be used to detect unknown objects in geological exploration, civil engineering and nuclear safety. Transmission imaging and scattering tomography schemes are studied. The transmission scheme uses a multilayer detector to measure the direction of a cosmic-ray muon passing through an object. The scattering scheme involves placing two detectors upstream and downstream of the object to record the incident and exit directions of the muon passing through the object. The effect of the detector resolution on the imaging clarity of transmission imaging was studied. The applicable scenarios of the two schemes were analyzed. The results by calculating show that in the transmission imaging of a hundred-meter object, a spatial resolution of 2.5 m can be achieved, and Cu and Fe can be discriminated with a density difference of 1.1 g/cm3. Scattering tomography is mainly suitable for meter-level objects, which can detect 0.2 m chamber and distinguish 0.05 m heavy metal blocks in rock.

A linear polarization conversion coding metasurface (MS) is proposed for the radar cross section (RCS) reduction of an object. The designed MS has both wideband RCS reduction and high efficiency of mirror reflection in different frequency bands. The cells are arranged according to different 1 bit coding sequences, and the characteristics of RCS reduction are verified by emulations and experiments. The simulation results indicate that the 01/10 coding MSs possess RCS reduction of greater than 10 dB in 9.5–13.9 and 15.2–20.4 GHz, and the 01/10 coding MS is less sensitive to polarization under normal incidence. The experiment results show that 10 dB RCS reduction is achieved in 10.2–14.0 and 15.3–20.7 GHz under normal incidence, and the relative bandwidth (BW) is 32% and 30%, while high efficiency of mirror reflection is obtained from 14.0 to 15.3 GHz. The experimental results are in good agreement with the numerical simulations. Additionally, for the 01/10 coding MS, the dual-broadband performance is also well maintained under 0°–45° oblique incidence. It is a new and practical method to suppress the scattering of metal objects by the combination of scattering and reflection, which has significant potential in the applications of antenna designs or stealth technology fields.

Super-resolution imaging has been revolutionizing technical analysis in various fields from biological to physical sciences. However, many objects are hidden by strongly scattering media such as biological tissues that scramble light paths, create speckle patterns and hinder object’s visualization, let alone super-resolution imaging. Here, we demonstrate non-invasive super-resolution imaging through scattering media based on a stochastic optical scattering localization imaging (SOSLI) technique. After capturing multiple speckle patterns of photo-switchable point sources, our computational approach utilizes the speckle correlation property of scattering media to retrieve an image with a 100-nm resolution, an eight-fold enhancement compared to the diffraction limit. More importantly, we demonstrate our SOSLI to do non-invasive super-resolution imaging through not only static scattering media, but also dynamic scattering media with strong decorrelation such as biological tissues. Our approach paves the way to non-invasively visualize various samples behind scattering media at nanometer levels of detail., The authors introduce stochastic optical scattering localization imaging (SOSLI) for non-invasive super-resolution imaging through scattering media. They capture multiple speckle patterns of photo-switchable point sources and use the speckle correlation to retrieve images with 100 nm resolution.

International audience; An experimental comparison is reported here between two equivalent resonant subwavelength metasurfaces made of long aluminum beams glued closely together on a thin aluminum plate. One metasurface has a random distribution of the resonator beams, and the other has a regular square lattice of pitch 1.5 cm. The random lattice shows the “resonant” behavior of a typical metasurface, with a wide full bandgap for the first A0 Lamb mode. Instead, the regular square lattice combines Fano resonance with Bragg scattering at the edges of the passband, thus creating anisotropy and a pseudo bandgap. Comparisons with numerical simulations are performed, with good agreement with the experimental data. The multimodal response of the beams is also responsible for double negativity in a narrow frequency band, and the event of a pseudo bandgap around this same flexural resonance. In addition, the scattering regimes for both the random and regular metasurfaces are characterized using coherent and incoherent signal analysis.