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Previous modeling studies have not properly explained the measured mass absorption cross section (MAC) at 550 nm, the linear backscattering depolarization ratio (LDR) at 355 and 532 nm, and the scattering matrix of soot at 532 nm. In this work, we attempt to use a black carbon (BC) model with an intrinsic organic carbon (OC) coating to explain the large MAC, large LDR, and measured scattering matrix. Our results show that the bare fractal BC model is not able to explain MAC, LDR, and scattering matrix simultaneously and that the modeling values do not cover the measurement range. This study shows that the modeled LDR and scattering matrix can cover the measurement range if we constrain the MAC of the BC in the measurement range by the intrinsic OC coating when we consider the effects of monomer radius, monomer number, and monomer overlap simultaneously. Therefore, intrinsic OC coating can be a significant source of uncertainty in the optical properties of fresh soot. Plain Language Summary: Since soot is the most important absorbing particle in the atmosphere, an accurate calculation of the optical properties of soot is of great importance for climate assessment and remote sensing. However, some of the observed optical properties of soot are difficult to explain with current models. In this study, a black carbon (BC) model with an intrinsic organic carbon (OC) coating is used to explain these difficult‐to‐explain optical properties. The results show that the simulated mass absorption cross section (MAC), linear backscattering depolarization ratio (LDR), and scattering matrix are difficult to explain when only the influence of BC is considered, although the effects of monomer size, monomer number, and monomer overlap are taken into account. Range of observation. However, after accounting for the intrinsic OC coating, the model is able to account for the range of realistic optical observations. Therefore, the intrinsic OC coating may be responsible for some optical properties that are difficult to explain with the current models. Key Points: The model of pure black carbon (BC) has difficulty explaining some optical observations of sootWe have proposed a soot model consisting of a BC core and an intrinsic organic carbon (OC) shellThe intrinsic OC coating may be a cause of some unexplained optical properties in current models [ABSTRACT FROM AUTHOR]

Light scattering holds immense significance in various applications, including LED lighting, display enhancement, and solar cell optimization, emphasizing the critical role of understanding scattering mechanisms, especially light–matter interactions, achieving effective optical diffusion. Consequently, the influence of stimuli on material properties, including refractive indices and thermal expansion behavior, has emerged as a pivotal consideration, leading to the development of stimuli‐responsive light scattering modifier. Here, a temperature‐sensitive light scattering modifier composed of poly(methyl methacrylate‐co‐styrene) and poly(ethylene‐co‐vinyl acetate) is presented as scattering particles and matrix, respectively, using a melt‐blending process. Optical properties are evaluated across controlled temperatures 0–70 °C. These findings demonstrate an increasing trend in diffuse transmission and haze as temperatures increased across all light scattering modifiers. Significantly, the optimized light scattering modifier, integrating a dual particle system, showcased uniform reduction gaps in parallel transmission and adjustable haze characteristics across the visible spectrum under temperature control. This optical modifier achieved a total transmission of 92% and adjustable haze levels ranging from 35% to 90% under temperature control. Furthermore, this fabrication of three‐layer films incorporating the light scattering modifier exhibited identical characteristics to the developed light scattering modifier, emphasizing their potential for seamless integration across diverse technological domains. [ABSTRACT FROM AUTHOR]

Non‐Hermitian metasurfaces with chiral exceptional points (EPs) in their scattering matrices have garnered significant attention due to their potential for optical polarization manipulation and wavefront control. However, existing approaches predominantly operate under normal incidence conditions, limiting their application in the manipulation of chiral EPs in momentum space. Here, the wavelength‐fixed manipulation of the chiral EPs across a wide‐range momentum space using a polyatomic metasurface is realized, which is attributed to the effective modulation of the collective interference of guided‐mode resonances excited by oblique transverse magnetic (TM) and transverse electric (TE) illuminations. Further, both theoretical and experimental analyses are conducted to explore the potential applications of the proposed design in the wavevector‐ and spin‐selective manipulation of reflection intensity and optical encryption. This work provides a straightforward method to realize and manipulate chiral EPs in momentum space at a fixed operational wavelength, paving the way for designing polarization‐selective and wavevector‐selective devices. [ABSTRACT FROM AUTHOR]

In this paper, a study of the coupled Schrödinger Maxwell-Bloch equations, which described the propagation of two optical pulses in an optical medium with coherent three-level atoms, is presented via the Riemann-Hilbert approach. First, we performed a spectral analysis on the basis of Lax pair with the negative flow, and then the Jost function, scattering matrix, and their analytic and symmetric properties are given. Second, the Riemann-Hilbert problem is established successfully through a standard dressing procedure via the Riemann-Hilbert approach, and then the potential function related to the solution of the Riemann-Hilbert problem is reconstructed. By introducing the special matrix functions, we can transform the irregular Riemann-Hilbert problem into the regular one, which can be solved by the Plemelj formula. Finally, some applications are given to solve the Riemann-Hilbert problem without reflection for the coupled Schrödinger Maxwell-Bloch equation, and the multi-soliton solutions are obtained explicitly. Moreover, the dynamic behaviors of some soliton solutions are discussed graphically by choosing appropriate parameters. [ABSTRACT FROM AUTHOR]

In a recent paper, it has been shown that, if an N‐port network fulfills the condition of (geometrical) unconditional stability at a given frequency, then its scattering parameters will also necessarily satisfy N easily computable bounds, one per port. In order to complete that picture, this contribution investigates whether a tighter bound can be obtained by combining the N$$ N $$ bounds into just one. The answer is in general negative, except that the 3‐port case does indeed exhibit a peculiar behavior: this can be exploited to reduce the upper bound when the diagonal elements of the scattering matrix are limited in magnitude up to some α$$ \alpha $$, and in particular for α=0$$ \alpha =0 $$ (simultaneous conjugate match). [ABSTRACT FROM AUTHOR]

Considering models with tilted linear and quadratic band touching dispersions, the effect of the transverse linear tilt on the transmission spectra is analyzed through a harmonically driven potential well oriented longitudinally. Employing the Floquet scattering matrix formalism, Fano resonances are found as an outcome of matching between the Floquet sidebands and quasi‐bound states, where the tilt renormalizes their energies and wave vectors. It is found that the Fano resonance energy decreases (increases) for linear (quadratic) band touchings as the magnitude of the transverse momentum increases, indicating a distinct signature of the underlying band dispersion in the transmission profile. The sign of the product of the transverse momentum and the tilt also determines the relative shift in the Fano resonance energy with respect to the untilted case for both band dispersions, suggesting a possible tunability of the Fano resonance for tilted systems. Importantly, the tilt strength can also be directly determined by measuring the Fano resonance energy as function of the transverse momenta direction. The shot noise spectra and their differential property are further studied where an inflection region and undulation, respectively, is found around the Fano resonance energy. Interestingly, differential shot noise and transmission spectra both qualitatively behave in a similar fashion and might thus serve as important observables for future experiments on driven solid‐state systems. [ABSTRACT FROM AUTHOR]

Leveraging topological properties in the response of electromagnetic systems can greatly enhance their potential. Although the investigation of singularity‐based electromagnetics and non‐Hermitian electronics has considerably increased in recent years in the context of various scattering anomalies, their topological properties have not been fully assessed. In this work, it is theoretically and experimentally demonstrated that non‐Hermitian perturbations around bound states in the continuum can lead to singularities of the scattering matrix, which are topologically nontrivial and comply with charge conservation. The associated scattering matrix poles, zeros, and pole‐zero pairs delineate extreme scattering events, including lasing, coherent perfect absorption, and absorber‐lasers. The presented framework enables a recipe for generation, annihilation, and addition of these singularities in electric circuits, with potential for extreme scattering engineering across a broad range of the electromagnetic spectrum for sensing, wireless power and information transfer, polarization control, and thermal emission devices. [ABSTRACT FROM AUTHOR]

Scanning transmission electron microscopy images can be complex to interpret on the atomic scale as the contrast is sensitive to multiple factors such as sample thickness, composition, defects and aberrations. Simulations are commonly used to validate or interpret real experimental images, but they come at a cost of either long computation times or specialist hardware such as graphics processing units. Recent works in compressive sensing for experimental STEM images have shown that it is possible to significantly reduce the amount of acquired signal and still recover the full image without significant loss of image quality, and therefore it is proposed here that similar methods can be applied to STEM simulations. In this paper, we demonstrate a method that can significantly increase the efficiency of STEM simulations through a targeted sampling strategy, along with a new approach to independently subsample each frozen phonon layer. We show the effectiveness of this method by simulating a SrTiO3 grain boundary and monolayer 2H‐MoS2 containing a sulphur vacancy using the abTEM software. We also show how this method is not limited to only traditional multislice methods, but also increases the speed of the PRISM simulation method. Furthermore, we discuss the possibility for STEM simulations to seed the acquisition of real data, to potentially lead the way to self‐driving (correcting) STEM. Lay Description: Scanning Transmission Electron Microscopy (STEM) simulation is used to validate contrast in experimental images through matching procedures. Parameter searches are performed over various combinations of aberrations and sample structures until an approximation is made with respect to the experimental image. The most common approach for calculating simulations is the multislice approach, where the sample potential is approximated as a series of two‐dimensional slices. The propagation of the beam between slices involves multiple Fast Fourier Transform calculations, which must be performed at all probe locations, hence it is computationally expensive. This means that STEM multislice simulations take a significant amount time to perform, even with specialist hardware such as graphical processing units for parallelisation of calculation. An alternative to this is a recently developed algorithm known as the plane‐wave reciprocal‐space interpolated scattering matrix (PRISM) method. PRISM uses the fact that the electron probe can also be expressed as a plane‐wave expansion, and a basis set of plane‐waves can be propagated through the sample (as in the multislice step) independently of one another. After the plane‐waves are propagated through the sample, they form what is known as a scattering matrix and can be superimposed with appropriate coefficients to approximate the exit wavefunction/probe. This makes PRISM significantly faster to compute exit probes, at a small expense of accuracy with respect to the ground truth multislice simulation. In this paper, we present a novel method for increasing STEM simulation computation time through targeted probe sub‐sampling. This method takes advantage of developments within the compressive sensing (CS) community, whereby a significant proportion of probe locations can be omitted during calculation, yet inpainted through a dictionary learning and sparse coding algorithms (such as Beta Process Factor Analysis, BPFA) with minimal loss of accuracy. The method is implemented with both the PRISM and multislice algorithms, and demonstrations of the method are applied to HAADF simulations of a low energy strontium titanate grain boundary, and the 2H phase of monolayer molybdenum disulfide with sulfur vacancies. The methods yield results which are functionally identical to the ground truth (fully sampled) multislice simulations, but can be performed up to 350× faster by using the PRISM method with sub‐sampling. Furthermore, we also demonstrate how STEM simulations can seed the recovery of experimental CS‐STEM data through (dictionary) transfer learning. This is applied to sub‐sampled HAADF images of yttrium silicide, and shows a 9% increase in PSNR versus only using BPFA. [ABSTRACT FROM AUTHOR]

A quantum pumping protocol through which the quasiparticles of Weyl/multi‐Weyl and nodal‐line semimetals are subjected to a time‐periodic rectangular potential well is considered. The presence of an oscillating potential of frequency ω creates equispaced Floquet side‐bands with spacing ℏω$\hbar \omega$. As a result, a Fano resonance is observed when the difference in the Fermi energy (i.e., the energy of the incident quasiparticle), and the energy of one of the (quasi)bound state levels of the well, coincides with the energy of an integer number of photons (each carrying energy quantum ℏω$\hbar \omega$). Using the Floquet theory and the scattering matrix approach in the zero‐temperature non‐adiabatic pumping limit, characteristic Fano resonance patterns are found in the transmission coefficients. The inflection points in the pumped shot noise spectra also serve as a proxy for the corresponding Fano resonances. Therefore, the pumped shot noise is also numerically evaluated. Finally, the existence of the Fano resonance points is correlated to the (quasi)bound states of the well, by explicitly calculating the bound states of the static well (which are a subset of the bound states of the driven system). Since semimetals with anisotropic dispersions are considered, all the features observed depend on the orientation of the potential well. [ABSTRACT FROM AUTHOR]

Exploiting topological ideas has been a major theme in modern photonics, which provides unprecedented opportunities to design photonic devices with robustness against defects. While most previous works in topological photonics have focused on band theory, recent theories extend the topological concepts to the analysis of scattering matrices and suggest a topological route to complete polarization conversion (CPC). Here, the experimental observation of the topological CPC is reported. Using angle-resolved reflection measurements, it is unveiled experimentally that the CPC between arbitrary two polarizations occurs at vortex singularities of reflection coefficients in momentum space, reflecting its topological nature. Besides, it is visualized directly that for a given input polarization, the output one can cover the entire Poincaré sphere over a wide frequency range by varying the incident angle, guaranteed by the topological nature of CPC, which is in sharp contrast to the conventional polarization-conversion approaches that usually suffer from the bulky volume, limited choice of eigen-polarization states, or narrow operation bandwidths. Remarkably, that BICs lie on the critical coupling curves that define the condition for CPC is experimentally demonstrated. This work paves the way to exploring the topological properties in scattering matrices for controlling light polarization and creating robust photonics devices. [ABSTRACT FROM AUTHOR]

The present study investigates the corrosion behavior of a Fe–Mn–Al–Ni–Cr shape memory alloy in a 5.0 wt% NaCl solution in combination with the functional properties. In a single crystalline condition, the investigated alloy shows a superior superelastic response with a maximum recovery strain of 5.2%. Furthermore, the results of the potentiodynamic polarization and impedance spectroscopy show that the addition of chromium generally improves corrosion resistance by increasing the resistance to localized corrosion. The single crystalline condition, which is characterized by an austenitic matrix and scattered martensite plates, shows an enhanced, however, still unstable passive behavior due to the formation of corrosion pits along the martensite plates. [ABSTRACT FROM AUTHOR]

We relate the scattering theory of the focusing AKNS system with vanishing boundary conditions to that of the matrix Schrödinger equation. The corresponding Miura transformation, which allows this connection, converts the focusing matrix nonlinear Schrödinger (NLS) equation into a new nonlocal integrable equation. We apply the matrix triplet method to derive the multisoliton solutions of the nonlocal integrable equation, thus proposing a new method to solve the matrix NLS equation. [ABSTRACT FROM AUTHOR]

In this paper, six kinds of periodic optical waveguide networks are designed to study the influence of three‐order parity–time‐symmetric (PT‐symmetric) substructures on the singular optical characteristics. It is found that different characteristics correspond to different PT‐symmetric substructures, and new singular optical characteristics are produced by adjusting the PT‐symmetric substructures. This work demonstrates that these six kinds of systems can create novel quasi‐blackbody, super reflection, and new total reflection, which are significantly different from the corresponding traditional properties and have not been reported yet. These findings may deepen the understanding of PT‐symmetric optical systems and optical waveguide networks, and these new characteristics may possess potential applications in the design of multifunctional optical structures with efficient information processing. [ABSTRACT FROM AUTHOR]

The Hartman effect refers to the rather paradoxical result that the time spent by a quantum mechanical particle or a photon to tunnel through an opaque potential barrier becomes independent of barrier width for long barriers. Such an effect, which has been observed in different physical settings, raised a lively debate and some controversies, owing to the correct definition and interpretation of tunneling times and the apparent superluminal transmission. A rather open question is whether (and under which conditions) the Hartman effect persists for inelastic scattering, that is, when the potential becomes non‐Hermitian and the scattering matrix is not unitary. Here, tunneling through a heterojunction barrier in the tight‐binding picture is considered, where the barrier consists of a generally non‐Hermitian finite‐sized lattice attached to two semi‐infinite nearest‐neighbor Hermitian lattice leads. A simple and general condition is derived for the persistence of the Hartman effect in non‐Hermitian barriers, showing that it can be found rather generally when non‐Hermiticity arises from nonreciprocal couplings, that is, when the barrier displays the non‐Hermitian skin effect, without any special symmetry in the system. [ABSTRACT FROM AUTHOR]

This letter proposes a high isolation two‐element multiple input multiple output (MIMO) antenna by using a wideband pixel neutralization line (NL). The design procedures are simplified as follows: (1) Obtaining the Y‐parameters of the original two‐element antenna with a grid of microstrip stubs, and discrete ports are inserted among microstrip stubs; (2) obtaining the binary codes of the optimum route. Importing Y‐parameters into MATLAB, and using a genetic algorithm to obtain the optimum connection route by design formulas upon scattering matrix which guarantees high isolation; (3) translating the binary codes into the actual connection metallic lines; (4) adding the designed pixel NL and appropriate matching branches into EM simulator to optimize the antenna; (5) obtaining a high isolation two‐element antenna. The original two‐element antenna has poor isolation with the main path coupling, and the pixel NL provides an auxiliary coupling path between two elements. By adjusting pixel NL, the magnitude strengths of two coupling signals realize the same, while the phases are exactly opposite. Therefore, the wideband high isolation between antenna elements is realized. To verify the practicability of the proposed pixel decoupling neutral line, a reference and proposed two‐element MIMO antennas are fabricated and measured. In the experiment, the isolation of the proposed two‐element antenna with an edge‐to‐edge distance of 0.0943λ0 (λ0 is the wavelength in free space at the center frequency) is enhanced by about 17 dB in the working frequency band from 0.975 to 1.025 GHz. Besides, an L‐typed feeding network is added to guarantee a good matching condition. The proposed two‐element antenna has a size of 0.617λ0 × 0.667λ0, and the dimension of each radiation patch is 0.3267λ0 × 0.0725λ0. The proposed GA algorithm‐based decoupling technique has a significant superiority over traditional ones. Efficient, simple, and one‐time EM simulation are its major advantages, which can liberate the RF engineer from the heavy debugging work. [ABSTRACT FROM AUTHOR]

We present a detailed study of the scattering system given by the Neumann Laplacian on the discrete half‐space perturbed by a periodic potential at the boundary. We derive asymptotic resolvent expansions at thresholds and eigenvalues, we prove the continuity of the scattering matrix, and we establish new formulas for the wave operators. Along the way, our analysis puts into evidence a surprising relation between some properties of the potential, like the parity of its period, and the behaviour of the integral kernel of the wave operators. [ABSTRACT FROM AUTHOR]

We derive dispersion estimates for solutions of a one‐dimensional discrete Dirac equations with a potential. In particular, we improve our previous result, weakening the conditions on the potential. To this end we also provide new results concerning scattering for the corresponding perturbed Dirac operators which are of independent interest. Most notably, we show that the reflection and transmission coefficients belong to the Wiener algebra. [ABSTRACT FROM AUTHOR]

The polarimetric distortions present in the polarimetric SAR (PolSAR) data sets leads to unexpected results from the polarimetric decomposition and classification models, which in turn result in the ground target misinterpretation. The most important polarimetric distortions in airborne PolSAR data sets are the channel imbalance and crosstalk. The minimization of these polarimetric distortions using polarimetric calibration techniques is very important to carry out the quantitative analysis using PolSAR data and time series analysis and to compare results between different sensors. In the current state of the art, the spatial variability of the polarimetric distortions at different slant‐range positions in the data set was not completely analyzed and also the temporal variability of the polarimetric distortions using multiple data sets needs to be more investigated. Therefore, the main objectives of this study were to develop an operational processor to perform the external polarimetric calibration of the L‐band Uninhibited Aerial Vehicle Synthetic Aperture Radar system and to analyze the spatio‐temporal behavior of the polarimetric distortions. The polarimetric distortion matrix (PDM) was formulated after considering the crosstalk and channel imbalance polarimetric distortions to derive the scattering matrix free from all kinds of polarimetric distortions from the observed scattering matrix. The Quegan, improved Quegan, and Ainsworth methods for polarimetric calibration were implemented to solve the PDM. The residual channel imbalance and crosstalk after polarimetric calibration were estimated to compare the calibration efficiency of these methods. After that, a spatio‐temporal analysis was carried out with several data sets to assess the spatio‐temporal behavior of these polarimetric distortions. The polarimetric signatures and the coherency matrix behavior of the trihedral corner reflectors were used to analyze the ground target characterization improvement after polarimetric calibration. The results obtained from this study revealed that the crosstalk is the major cause for the polarimetric distortions and the channel imbalance and phase bias present in the data sets were not high. From the spatio‐temporal analysis, it was found that the variability of these polarimetric distortions both in spatial and temporal domains was minimum and can be discarded without causing any considerable error in the polarimetric calibration process. Key Points: The major cause for the polarimetric distortions in the UAVSAR data sets was due to the crosstalkThe channel imbalance and phase bias distortions were not high for all the data setsPolSAR calibration involves the use of Quegan, Improved Quegan, and Ainsworth methods in this study [ABSTRACT FROM AUTHOR]

The significant contribution of this paper is to present a comprehensive analysis and design of π‐point and band edge frequencies of reported helix SWSs including not only a microwave but also millimeter‐wave operation frequencies considering the methods in available literature which are the Coupled Mode Analysis (CMA), the Exact Floquet Approach (EFA), and the Auxiliary Functions of Generalized Scattering Matrix (AFGSM) as a comparative study. A different approach called as effective rod model is applied to circular/T‐shaped dielectric support rod helix SWSs in order to obtain ladder circuit representation of one turn of related helix SWSs for the first time. Scattering matrices of equivalent circuit representation of interested helix SWSs are obtained by using microstrip line model of helix SWS which slits helical tape at the effective helix radius along the direction normal to the helix winding direction and flattens it out for the EFA, the AFGSM, and the CMA methods. Additionally, comparisons are given for investigated methods together with the results of Computer Simulation Technology (CST) design environment, and good agreement has been observed among numerical results of different helix SWSs in a broad frequency range. [ABSTRACT FROM AUTHOR]

It is shown that information on the spatial correlation of nano‐objects embedded in a crystalline matrix can be retrieved by analysing the X‐ray scattering around the Bragg reflections of the host matrix. Data are reported for vertically aligned Ni and CoNi alloy nanowires (NWs) in an SrTiO3 matrix. When the Bragg condition is fulfilled for the matrix and not for the NWs, the latter can be approximated by voids, and the scattering around the matrix reflections contains information on the self‐correlation of the NWs (i.e. on their diameter d) and on the correlation between NWs (interdistance D). Nondestructive synchrotron X‐ray diffraction data provide information on these values averaged over large areas, complementing local transmission electron microscopy observations. The measurements show that off‐Bragg scattering around the matrix reflections can be exploited to study the spatial correlation and morphology of embedded nano‐objects, independently of their crystallinity or strain or the presence of defects. [ABSTRACT FROM AUTHOR]

A novel design of the polarizer based on a square waveguide with four posts and four irises for Ku‐band 10.7–12.8 GHz is proposed. The main advantage of the developed polarizer design is the option to tune its polarization characteristics by variation of the posts height. The equivalent circuit of the polarizer has been obtained using scattering and transfer matrices technique. Using this model, the polarization and matching characteristics of the suggested polarizer were optimized simultaneously using the trust region method. This method is reliable and robust since it provides good convergence properties. The novelty of this study lies in the use of a new waveguide polarizer structure based on a combination of irises and posts. Posts enable fine‐tuning of the polarizer performance, while irises promote wide operating frequency band. The following simulated characteristics of the optimal polarizer design were obtained: VSWR for the main modes of horizontal and vertical polarization is less than 1.47, the differential phase shift is within 90° ± 2.6°, the axial is less than 0.46 dB, and the XPD is higher than 32 dB in the operating frequency range. A developed polarizer can be applied in antenna feeds for satellite communication and radar systems. [ABSTRACT FROM AUTHOR]

Germanium self‐assembled nanoislands and quantum dots are very prospective for CMOS‐compatible optoelectronic integrated circuits but their photoluminescence (PL) intensity is still insufficient for many practical applications. Here, it is demonstrated experimentally that the PL of Ge nanoislands in silicon photonic crystal slabs (PCS) with hexagonal lattice can be dramatically enhanced due to the involvement in the emission process of the bounds states in the continuum. These high‐Q photonic resonances allow to achieve PL resonant peaks with the quality factor as high as 2200 and with the peak PL enhancement factor of more than two orders of magnitude. The corresponding integrated PL enhancement is demonstrated to be more than one order of magnitude. This effect is studied theoretically by the Fourier modal method in the scattering matrix form. The symmetry of the quasi‐normal guided modes in the PCS is described in terms of group theory. This work paves the way toward a new class of optoelectronic components compatible with silicon technology. [ABSTRACT FROM AUTHOR]

Non‐Hermitian photonic systems capable of perfectly absorbing incident radiation recently attracted much attention both because fundamentally they correspond to an exotic scattering phenomenon (real‐valued scattering matrix zero) and because their extreme sensitivity holds great technological promise. The sharp reflection dip is a hallmark feature underlying many envisioned applications in precision sensing, secure communication, and wave filtering. However, a rigorous link between the underlying scattering anomaly and the system's sensitivity to a perturbation is still missing. Here, a theoretical description in complex scattering systems is developed which quantitatively explains the reflection dip's shape. It is furthermore demonstrated that coherent perfect absorption (CPA) is associated with a phase singularity and that the sign of the diverging time delay is related to the mismatch between excitation rate and intrinsic decay rate. The theoretical predictions are confirmed in experiments based on a 3D chaotic cavity excited by eight channels. Rather than relying on operation frequency and attenuation inside the system to be two free parameters, "on‐demand" CPA is achieved at an arbitrary frequency by tweaking the chaotic cavity's scattering properties with programmable meta‐atom inclusions. Finally, the optimal sensitivity of the CPA condition to minute perturbations of the system is proven theoretically and verified experimentally. [ABSTRACT FROM AUTHOR]

"Fully polarimetric" in its original radio science usage denotes a receiving instrument's ability to measure the four‐parameter Stokes vector characterizing the polarimetric properties of an electro‐magnetic (EM) field. In contrast, radar remote sensing specialists use "fully polarimetric" to apply exclusively to radars that evaluate the four complex scattering matrix elements. To disambiguate, polarimetric portrait is suggested, defined to be the Stokes vector of an unbiased EM field. For a passive system, this new name applies without qualification to the four Stokes parameters seen through a passive dual‐channel receiver. For an active system, the scene's illumination must have equal weighting between any two orthogonal polarizations to generate a polarimetrically unbiased reflected EM field. The suggested terminology is applicable to a variety of disciplines, including radiometry, alternative polarimetric radar architectures, radar astronomy, weather radar, and GPS/GNSS reflectometry. Polarimetric portraits obtained by dual‐polarized and quadrature‐polarized radars are shown to be equal. Key Points: "Fully polarimetric" re: electromagnetic measuring systems has conflicting meanings; to disambiguate: "polarimetric portraits" is proposedA physical optics‐based calculation proves the equivalence of polarimetric portraits from dual‐ and quadrature‐polarized radarsGPS/GNSS reflectometry data are sufficient to support polarimetric portraits, enabling new science opportunities [ABSTRACT FROM AUTHOR]

In this paper, we study the Jost solutions of the impulsive Dirac systems (IDS) on entire axis and examine analytic and asymptotic properties of these solutions. Furthermore, we obtain a general form of the scattering matrix of the IDS and its characteristic properties. Finally, we also compare the similar properties for the IDS with the mass on entire axis with an example. [ABSTRACT FROM AUTHOR]

In this paper, a new method‐of‐moments‐based approach is proposed for the analysis of non‐uniform lossy substrate integrated waveguides (SIW) transmission lines. The approach incorporates Chebyshev expansion in the frequency domain to compute the scattering parameter matrix of the line. To validate the proposed approach of non‐uniform structures are analyzed where two of them have been fabricated and measured. The analytical and measured S parameters were compared to those obtained through electromagnetic finite element‐based simulations. The good match observed between the two sets of results for a relatively reasonable number of basis functions confirms the accuracy and the fast convergence of the proposed approach. This makes it the most suitable for integration into computer‐aided design tools. [ABSTRACT FROM AUTHOR]

Purpose: To obtain efficient operation modes of transmit array (TxArray) coils using a general design technique based on the eigenmode analysis of the scattering matrix. Methods: We introduce the concept of modal reflected power and excitation eigenmodes, which are calculated as the eigenvalues and eigenvectors of SHS, where the superscript H denotes the Hermitian transpose. We formulate the normalized reflected power, which is the ratio of the total reflected power to the total incident power of TxArray coils for a given excitation signal as the weighted sum of the modal reflected power. By minimizing the modal reflected power of TxArray coils, we increase the excitation space with a low total reflection. The algorithm was tested on 4 dual‐row TxArray coils with 8 to 32 channels. Results: By minimizing the modal reflected power, we designed an 8‐element TxArray coil to have a low reflection for 7 out of 8 dimensions of the excitation space. Similarly, the minimization of the modal reflected power of a 16‐element TxArray coil enabled us to enlarge the dimension of the excitation space by 50% compared with commonly employed design techniques. Moreover, we demonstrated that the low total reflected power for some critical excitation modes, such as the circularly polarized mode, can be achieved for all TxArray coils even with a high level of coupling. Conclusion: Eigenmode analysis is an efficient method that intuitively provides a quantitative and compact representation of the coil's power transmission capabilities. This method also provides insight into the excitation modes with low reflection. [ABSTRACT FROM AUTHOR]

An inclusive method is introduced for the analysis of different types of inductively loaded rectangular waveguides with dielectric and/or metallic obstacles. The proposed method utilizes the efficiency of the generalized scattering matrix (GSM) method on scattering analysis and the flexibility of the method of moments on problem configuration. The inductive metallic discontinuities are treated as a dielectric medium with high conductivity and the scattering analysis is accelerated by several cost reduction attempts in conjunction with GSM method and procedure of method of moments. The examined approach is tested against several structures including a metal insert filter, an H‐plane filter, and a dielectric‐metal obstacle‐loaded waveguide both for the dominant mode region and the double‐mode region. The convergence analyses on the number of calculated modes and the size of the discretized cells in the computational procedure are carried out for a comprehensive explanation of the numerical analysis. The accuracy of the method is compared to commercial software based on the finite element method. The proposed method is particularly competent for the frequency analysis of metallic and inhomogeneous dielectric discontinuities horizontally aligned in cuboid shapes. [ABSTRACT FROM AUTHOR]

The total amplitude reflection coefficient of EM wave in a nonuniform plasma slab coated on perfect conductor plane is newly derived by using the scattering matrix method (SMM), and the attenuation is calculated. Three types of plasma electron density profile, that is the hyperbolic, sinusoidal, and linear profiles, are used. The external magnetic field and plasma parameters such as the maximum electron density and collision frequencies are discussed to calculate the attenuation of EM wave. The calculation results show that the plasma electron density profile and maximum electron density exert a large effect to the attenuation of EM wave and the attenuation under the uniform external magnetic field is taken place by the electron cyclotron resonance absorption, the up hybrid resonance absorption and geometric resonances absorption. [ABSTRACT FROM AUTHOR]

Two forms of carbon‐rich microfossils were discovered in the breccias of the Onaping Formation, Sudbury impact structure. The first form is represented by single particles scattered in the matrix of the breccias and included in the vesicles in altered glass. These particles are leaf‐shaped, stem‐shaped, tubular, and spherical objects ranging from 5–10 μm to 200–300 µm in size. It is suggested that algal flora inhabiting the ocean basin before the Sudbury impact was the source of plant material in the Onaping Formation. The second form of carbon‐rich microparticles in the Onaping Formation is represented by plant detritus in carbon‐bearing fragments of mudstones included in the breccia matrix. The microparticles in the mudstones are mainly ribbon‐like shreds from 3–5 µm to 200–300 µm long, while rare particles have more complex shapes. The matrix of the mudstones is a fine‐grained clay‐like substance with a network of micron‐wide open‐joint fissures. Contents of carbon in the mudstone matrix are 12–15 wt%. Muddy bottom sediments of the pre‐impact sea are supposed as a source of mudstone fragments in the breccias. Fragments of mudstones and carbon‐rich microparticles are an important source of organic carbon in the breccias of the Onaping Formation. Discovery of microfossils in the breccias of the Onaping Formation suggests the presence of a previously unknown complex algal flora that inhabited the pre‐impact sea before the impact event 1.85 billion years ago at the very end of the Paleoproterozoic. [ABSTRACT FROM AUTHOR]

Target characterization is an essential aspect of polarimetric decomposition. This technique is capable of categorizing polarimetric signatures for different types of targets based on the scattering mechanisms they follow, enabling straightforward physical interpretation of the targets. The geometric anomalies associated with human‐made targets escalate the degree of randomness in the scattering process, which causes scattering ambiguity for such targets. The second‐order model descriptors do not relate to the actual physical structure and yield predominant volume scattering power. Such urban targets are decomposed as natural targets leading to irrelevant decomposition results. The methods developed to curb the problem are unable to maintain the consistency in the decomposition modeling as they underestimate volume scattering powers for natural landcover. A hybrid decomposition model is proposed herein to solve the problem of predominant volume scattering observed from urban targets by preserving volume scattering powers for natural targets. The model uses eigenvalue‐based decomposition parameters and polarimetric interferometric synthetic aperture radar (PolInSAR) coherence to decompose ambiguous targets. The proposed model has been tested on NISAR UAVSAR PolInSAR data acquired over the Greenville region, MS, USA. The proposed model has increased the double‐bounce scattering from the urban targets and enhanced the volume scattering from natural landcover as well. By comparing the results with existing decomposition models, it is observed that the proposed model gives a more robust representation of the landcover than the compared decomposition models. Plain Language Summary: The SAR sensor illuminates the surface with polarized microwaves and receives the interacted backscattered wave. The backscattered wave is transformed into information, which is represented by a scattering matrix. Due to different geophysical properties of the targets, there is a change in the backscattered wave. Polarimetric SAR decomposition is a technique that can relate the change in backscatter to the physical structure of the target, enabling simple and robust classification of the landcover. The techniques decompose or disintegrate the scattering matrix into scattering mechanisms, and each scattering mechanism represents a broad category of different landcover. Owning to the random nature of real‐world observations, the backscatter for two different categories of landcover can be the same, such as a building and a tree. Therefore, for such cases, the polarimetric decomposition yields inaccurate classification results, and from the polarimetric point of view, this problem is referred to as overestimation of volume scattering. The reason for this is the assumptions and the design of the model. Various modifications have been proposed to solve the problem of overestimation. We find that direct modification may yield inconsistent decomposition results, which can be critical for different utilities of polarimetric decompositions. We propose a new model that associates SAR interferometry with polarimetric decompositions to solve the problem of predominant volume scattering. The new model has been tested on L‐band simulated NISAR UAVSAR data acquired over the Greenville region, MS, USA. Key Points: PolInSAR coherence to characterize targets as permanent or dynamic featuresEntropy describes the randomness of the scattering processModel‐based decompositions have been proposed for the scattering‐based characterization of manmade and natural features [ABSTRACT FROM AUTHOR]

A model for an artificial neuron (AN) is introduced which is based on ballistic transport in a multiterminal device. Unlike standard configurations, the proposed design embeds the synaptic weights into the active region, thus significantly reducing the complexity of the input terminals. This is achieved by defining the basic elements of the ballistic AN as follows: the input values are set by the incoming wavefunctions amplitudes, whereas the weights correspond to the scattering matrix elements. Furthermore, the output value of the activation function of the AN is given by the transmission function. By tuning the gate voltage, the scattering potential and, consequently, the weights are changed so that the value of the transmission function gets closer to the target output, which is essential in the training process of artificial neural networks. Thus, the modus operandi of a ballistic AN is provided. [ABSTRACT FROM AUTHOR]

In this letter, a passive ultra‐wideband balun with high balance performance is proposed. The balun is realized by using a pair of planar spiral coupled transmission lines and a capacitor which is responsible for the capacitive balance compensation. The straight‐forward scattering matrix derivation shows that the proposed structure can achieve full output balances both in amplitude and phase. For demonstration, two baluns with and without the compensating capacitor were designed and fabricated in a 65‐nm complementary metal‐oxide‐semiconductor (CMOS) process. The measured results show that the compensated balun features a measured insertion loss ≤5.2 dB and a return loss ≥10 dB from 3.6 to 8.1 GHz. Within such a wide frequency range, the measured amplitude and phase difference are ≤0.2 dB and 1.8°, respectively, which are much better than its uncompensated counterpart. [ABSTRACT FROM AUTHOR]

A new theoretical approach is proposed for the performance simulation of multijunction (MJ) solar cells, starting from the weakness and strength of the Hovel model and of the transfer matrix method for describing the propagation of electromagnetic waves inside the solar cell structure. It is based on the scattering matrix method (SMM) and on a simplified generation function that allow describing with good accuracy the propagation of electromagnetic waves in the solar cell device, preserving, at the same time, the possibility of getting simple analytical solutions of the continuity equations. The numerical stability of the new theoretical approach is first demonstrated on triple junction InGaP/InGaAs/Ge solar cells, in which the Ge substrate is considered as the last layer (layer N) and then as the N‐1 layer. Further, the new theoretical approach is applied to simulate the performance of thin quadruple junction (QJ) InGaP/InGaAs/SiGeSn/Ge solar cells, in two‐ and three‐terminal configurations. Efficiency values of up to 45.1% and 44.9%, respectively, have been simulated at 1000× concentration, by considering the MJ limited by the InGaAs subcell. Finally, it is estimated that the QJ InGaP/InGaAs/SiGeSn/Ge solar cell has the potential to reach efficiencies over 50% by assuming proper antireflective coatings. [ABSTRACT FROM AUTHOR]

The acceptance–rejection technique has been widely used in several Monte Carlo simulation packages for Rayleigh scattering of photons. However, the models implemented in these packages might fail to reproduce the corresponding experimental and theoretical results. The discrepancy is attributed to the fact that all current simulations implement an elastic scattering model for the angular distribution of photons without considering anomalous scattering effects. In this study, a novel Rayleigh scattering model using anomalous scattering factors based on the inverse‐sampling technique is presented. Its performance was evaluated against other simulation algorithms in terms of simulation accuracy and computational efficiency. The computational efficiency was tested with a general‐purpose Monte Carlo package named Particle Transport in Media (PTM). The evaluation showed that a Monte Carlo model using both atomic form factors and anomalous scattering factors for the angular distribution of photons (instead of the atomic form factors alone) produced Rayleigh scattering results in closer agreement with experimental data. The comparison and evaluation confirmed that the inverse‐sampling technique using atomic form factors and anomalous scattering factors exhibited improved computational efficiency and performed the best in reproducing experimental measurements and related scattering matrix calculations. Furthermore, using this model to sample coherent scattering can provide scientific insight for complex systems. [ABSTRACT FROM AUTHOR]

Purpose: The scattering matrix (S‐matrix) of a parallel transmit (pTx) coil is sensitive to physiological motion but requires additional monitoring RF pulses to be measured. In this work, we present and evaluate pTx RF pulse designs that simultaneously excite for imaging and measure the S‐matrix to generate real‐time motion signals without prolonging the image sequence. Theory and Methods: Three pTx waveforms for measuring the S‐matrix were identified and superimposed onto the imaging excitation RF pulses: (1) time division multiplexing, (2) frequency division multiplexing, and (3) code division multiplexing. These 3 methods were evaluated in healthy volunteers for scattering sensitivity and image artefacts. The S‐matrix and real‐time motion signals were calculated on the image calculation environment of the MR scanner. Prospective cardiac triggers were identified in early systole as a high rate of change of the cardiac motion signal. Monitoring accuracy was compared against electrocardiogram or the imaged diaphragm position. Results: All 3 monitoring approaches measure the S‐matrix during image excitation with quality correlated to input power. No image artefacts were observed for frequency multiplexing, and low energy artefacts were observed in the other methods. The accuracy of the achieved prospective cardiac gating was 15 ± 16 ms for breath hold and 24 ± 17 ms during free breathing. The diaphragm position prediction accuracy was 1.3 ± 0.9 mm. In all volunteers, good quality cine images were acquired for breath hold scans and dual gated CINEs were demonstrated. Conclusion: The S‐matrix can be measured during image excitation to generate real‐time cardiac and respiratory motion signals for prospective gating. No artefacts are introduced when frequency division multiplexing is used. [ABSTRACT FROM AUTHOR]

The article discusses the enhancement of the photo-response threshold in Ag-NP/TiO2 composite thin films by adsorbing chlorophyll dye extracted from mopane leaves onto them. This advancement allows for the creation of photocathodic p-DSSCs with high concentrations of Ag evenly scattered in a TiO2 matrix. The efficacy of this electrode is the highest ever reported for a p-type working Ag/TiO2/chlorophyll/iodine electrode, which may have potential applications in photo-sensitizer tandem devices. The article is authored by Likius S. Daniel, Rocha T. Kaffer, Loini M. Kalipi, Ateeq Rahman, Mbela Kalengay, and Veikko Uahengo. [Extracted from the article]

In radar systems, transmitting and receiving waveforms with different polarisations benefit to acquire complete information about the target and its environment, ensuring significant enhancement of the radar's performance. Here, the authors consider the optimisation problem of jointly designed transmitter and receiver (TR) polarisation from the view of target scattering estimation. Under the condition that the target and clutter scattering covariance is known as a prior, they first use sequential linear minimum mean square error estimation to obtain the target scattering matrix and then optimise the sensing vector, which contains the polarisation information under the constraint of minimising the mean square error. The mentioned problem can be solved by eigenvector decomposition. Then, a method to get the TR polarisation parameters is provided. Finally, they use numerical simulations to show the advantage of the proposed methods. [ABSTRACT FROM AUTHOR]

The purpose of this study is to demonstrate that the fully polarimetric radar can be effectively used to measure the insect orientation. First, the polarisation scattering matrix (PSM)-based orientation extraction method is reviewed. This method was proposed for traditional rotation polarisation radar, but is also applicable to fully polarimetric radar. Then, both anechoic chamber and field experiments were conducted to measure fully polarimetric insect PSMs and orientations, which verified the effectiveness of insect orientation extraction based on fully polarimetric measurement. [ABSTRACT FROM AUTHOR]

Based on a pair of linear frequency modulation waveforms with opposite slopes, the mathematical model of the influence of intermediate frequency deviation (IFD) and sampling frequency deviation (SFD) on simultaneous polarisation measurement is derived. An IFD and SFD joint estimation and calibration method is proposed in this article. Simulation and real data results show that the radar frequency stability can change the position and phase of the polarisation scattering matrix (PSM) measurement. The approach proposed in this article can regulate the peak deviation effectively, compensate the phase error and accurately acquire the four elements of PSM. [ABSTRACT FROM AUTHOR]

Polarimetric SAR (PolSAR) data can be characterised by scattering matrix, which contains four elements. It is difficult to merge all the elements of the scattering matrix for segmentation. On the other hand, a PolSAR image contains objects of various scales, so segmentation on a single scale may lead to over-segmentation and under-segmentation. To address these two problems, an adaptive scale segmentation algorithm for PolSAR image is proposed. First, extract a synthetic gradient image that contains scattering information of all polarisation channels. Second, to prevent the over-segmentation of the watershed algorithm, extract the markers of the synthetic gradient image adaptively. Finally, combined with the result of PolSAR classification, the segmentation scales are adaptively selected for the segmentation of the synthetic gradient image. The results show that the proposed algorithm can not only accurately extract the segmentation boundaries of different objects but also overcome the over-segmentation of large-scale objects and under-segmentation of small-scale objects. Compared to fixed scale segmentation algorithms, the segmentation result of the proposed algorithm has the best quantitative index, that is, the lowest global heterogeneity evaluation index. [ABSTRACT FROM AUTHOR]

The Pancharatnam‐Berry phase optical elements (PBOEs) are utilized to enhance the performance of head‐up displays (HUDs). The PB lenses provide varifocal functionality, while the PB deflectors can function as optical combiners and waveguide couplers. Rigorous coupled wave analysis based on scattering matrix is also developed and applied for structure optimization. [ABSTRACT FROM AUTHOR]

The electron effective mobility analytical model without empirical parameters is investigated for uniaxial strained Si inversion layer, which can be conveniently applied by device and circuit designers. By one‐dimensional inverse transform for the three‐dimensional (3D) scattering matrix element along the vertical channel direction, three scattering (coulomb scattering, acoustic phonon scattering and intervalley scattering) rate models are researched. Then, the surface roughness scattering rate is taken into account to calculate the 2D inversion layer electron mobility. Based on the models, the simulations have been carried out by Matlab. The simulation results are in accord with the reference data, and the saturation phenomenon is brought to light. [ABSTRACT FROM AUTHOR]

The Pancharatnam‐Berry optical elements (PBOEs) are utilized to enhance the performance of head‐up displays (HUDs). The Pancharatnam‐Berry lenses (PBLs) provide varifocal functionality and compensate chromatic aberrations, while the Pancharatnam‐Berry deflectors (PBDs) can function as optical combiners and waveguide couplers. Moreover, the Rigorous coupled wave analysis (RCWA) based on the scattering matrix is developed and applied in the structure optimization of PBOEs for HUD applications. Cost‐effective functional liquid crystal optical elements employing Pancharatnam‐Berry phase are helpful for enhancing the performance of head‐up displays. These distinct optical elements enable switchable virtual‐image‐distance and look‐down‐angle, and function as polarization sensitive optical combiners and high‐efficiency grating couplers for waveguide‐based HUDs. [ABSTRACT FROM AUTHOR]

The well‐known symmetry property of the scattering matrix relative to propagating modes becomes tricky in the case of arbitrary polarization or arbitrary complex modal functions, as in the case of waveguide polarizers and ortho‐mode transducers. A straightforward transformation between different modal bases for the guided waves leads to a loss of symmetry. Only by gaining a deeper insight on the properties of the scattering matrices and with separate transformations for the incident and reflected waves is symmetry recovered. [ABSTRACT FROM AUTHOR]

We study the well-posedness of the linearized water-wave problem in a periodic channel with fixed or freely floating compact bodies. Floquet-Bloch-Gelfand-transform techniques lead to a generalized spectral problem with quadratic dependence on a complex parameter, and the asymptotics of the solutions at infinity can be described using Floquet waves. These are constructed from Jordan chains, which are related with the eigenvalues of the quadratic pencil and which are calculated in the paper in some typical cases. Posing proper radiation conditions requires a careful study of spaces of incoming and outgoing waves, especially in the threshold situation. This is done with the help of a certain skew-Hermitian form q, which is closely related to the Umov-Poynting vector of energy transportation. Our radiation conditions make the problem operator into a Fredholm operator of index zero and provides natural (energy) classification of outgoing/incoming waves. They also lead to a novel, most natural properties and interpretation of the scattering matrix, which becomes unitary and symmetric even at threshold. [ABSTRACT FROM AUTHOR]

A comparative analysis of three different time-independent approaches to studying open quantum structures in a uniform electric field [ABSTRACT FROM AUTHOR]

Using the Floquet theory and the scattering matrix approach, in the zero-temperature non-adiabatic pumping limit, characteristic Fano resonance patterns are found in the transmission coefficients, which depend on the nature of the dispersion. See article number 2200460 for more details. B Quantum Pumping b When quasiparticles of Weyl/multi-Weyl and nodal-line semimetals are subjected to a time-periodic potential well, the presence of the oscillating potential of frequency creates equispaced Floquet side-bands. [Extracted from the article]

A problem of scattering by a resonator connecting two 2D waveguides is studied. The incident wave is one of the waveguide modes taken at the spectral parameter close to a threshold of the continuous spectrum. It is shown that in the general case the reflection coefficient for such a mode is close to -1 (this case corresponds to an almost perfect reflection). Also it is shown that in some special cases the reflection coefficient is close to 0, and an almost perfect transmission is observed. The behavior of scattering at near-threshold frequencies is determined by solutions corresponding to the threshold spectral parameter and crucially depends on whether stabilizing solutions do exist or not. Anomalous transmission is observed when there exist only solutions growing at infinity. [ABSTRACT FROM AUTHOR]

This study presents the design and analysis of linear as well as cubic spline interpolated profiled smooth-wall multimode horn using mode matching (MM) technique along with genetic algorithm (GA) and particle swarm optimisation (PSO). To apply the MM technique, the smooth profile conical geometry is assumed to consist of cascaded sections of large number of small symmetrical radial steps. Scattering matrix for each section has been calculated using MM technique and over all scattering matrix of the cascaded junctions has been calculated using generalised scattering matrix technique. The radiation pattern has been calculated using hybrid boundary contour mode matching technique. Optimisation of the linear/spline profile horn has been carried out using GA as well as PSO. Detailed modal analysis along with the convergence of the present technique for the smooth profile structure has also been carried out. A spline profile multimode horn working at 89 GHz has been designed and developed. The present analysis has been verified with the measured results. There is a very good agreement between theoretical and measured results. [ABSTRACT FROM AUTHOR]