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The occurrence of quasi-bound states in the continuum (qBIC) in all-dielectric asymmetric grating waveguide couplers with different degrees of asymmetry under normal light incidence is analysed from the viewpoint of identifying the most promising configuration for realizing the highest quality (Q) factor under the condition of utmost efficiency (i.e. total extinction). Considering asymmetric gratings produced by altering every N th ridge of a conventional (symmetric) grating coupler, we analyse different regimes corresponding to the interplay between diffractive coupling to waveguide modes and band gap effects caused by the Bragg reflection of waveguide modes. The symmetric and double- and triple-period asymmetric grating couplers are considered in detail for the same unperturbed two-mode waveguide and the grating coupler parameters that ensure the occurrence of total transmission extinction at the same wavelengths. It is found that the highest Q is expected for the double-period asymmetric grating, a feature that we explain by the circumstance that the first-order distributed Bragg resonator (DBR) is realized for this configuration while, for other configurations, the second-order DBR comes into play. Experiments conducted at telecom wavelengths for all three cases using thin-film Al 2 O 3 -on-MgF 2 waveguides and Ge diffraction gratings exhibit the transmission spectra in qualitative agreement with numerical simulations. Since the occurrence of considered qBIC can be analytically predicted, the results obtained may serve as reliable guidelines for intelligent engineering of asymmetric grating waveguide couplers enabling highly resonant, linear and nonlinear, electromagnetic interactions.

The object of the study is the resonant effects of electromagnetic wave scattering by two silver nanoparticles in the optical range. The study considered the problem of the influence of the electromagnetic interaction between nanoparticles on the characteristics of light scattering and absorption by a model of two silver nanoparticles and determining the limit when this interaction can be neglected. Methods for calculating the scattering characteristics by this model are proposed. The methods are based on solving the system of surface integral Muller equations for a set of nanoparticles. The values of the total scattering, attenuation and absorption cross sections for a model of two ellipsoidal nanoparticles of different sizes with variable distances between them on two orthogonal polarizations are obtained. The first model consists of two nanoparticles with semi-axes of 75 × 75 × 25 nm, the second – 100 × 100 × 20 nm. The calculations were performed taking into account the electromagnetic interaction between nanoparticles when determining the current densities on their surfaces and without taking into account the specified interaction. As a numerical measure of the degree of electromagnetic interaction, the relative error in the calculation of the scattering characteristics of the models when taking into account the interaction and when neglecting it was used. The estimation of the limiting distances at which the interaction between nanoparticles can be neglected with a given accuracy was carried out. For an error in the calculation of scattering cross sections of less than 5% at a wavelength of λ = 300 nm, the limiting distance is from 0.4λ to 3λ (from 120 nm to 900 nm) depending on the polarization. The use of the approximate method at these distances while maintaining accuracy allowed to reduce the dimensionality of the system of integral equations by a factor of 4, which significantly reduced the computational costs. The proposed method can be generalized to nanoparticles of different sizes and from other noble metals.

Anapole modes of all-dielectric nanostructures hold great promise for many nanophotonic applications. However, anapole modes can hardly couple to other modes through far-field interactions, and their near-field enhancements are dispersed widely inside the nanostructures. These facts bring challenges to the further increasing of the response of an anapole mode. Here, we theoretically show that an anapole mode response in a dielectric nanostructure can be boosted through electromagnetic interactions with the coupling distance of a wavelength scale, which is beyond both the near-field and far-field limits. The all-dielectric nanostructure consists of a disk holding an anapole mode and a ring. Both analytical calculations and numerical simulations are carried out to investigate the electromagnetic interactions in the system. It is found that the electric dipoles associated with the fields of the anapole mode on the disk undergo retardation-related interactions with the electric dipoles associated with the ring, leading to the efficiently enhanced response of the anapole mode. The corresponding near field enhancement on the disk can reaches more than 90 times for a slotted silicon disk-ring nanostructure, where the width of the slot is 10 nm. This enhancement is about 5 times larger than that of an individual slotted disk. Our results reveal the greatly enhanced anapole mode through electromagnetic couplings in all-dielectric nanostructures, and the corresponding large field enhancement could find important applications for enhanced nonlinear photonics, near-field enhanced spectroscopies, and strong photon–exciton couplings.

Electromagnetic forming, by combining multiple coils and multiple capacitor banks, is an emerging manufacturing method that can produce flexible spatial-temporal patterns of the Lorentz force to shape metal workpiece. In this process, the polarity of the discharge currents is a key element because it determines the polarity of the magnetic field that is individually induced by each coil, which in turn affects the resulting magnetic field, the Lorentz force, and ultimately the deformation of the workpiece. Aiming to evaluate the potential effects of coil polarity, this paper performed a comparative experimental and numerical study, using a dual-coil system. It is found that the workpiece deformation is sensitive to the coil polarity with respect to both energy efficiency and performance. Furthermore, the analysis of the electromagnetic dynamics shows that the coil polarity would affect the workpiece deformation by altering the electromagnetic interaction between the coils and the workpiece. In this way, both the discharge currents on the coils and the eddy currents on the workpiece would be altered. And consequently, the produced Lorentz forces and thereby the workpiece deformation are affected. The results in this study can be useful for the coil polarity selection that is required in multi-coil forming processes.

An electron moving at velocities much lower that the speed of light with a spin, is described by a wave function which is a solution of Pauli’s equation. It has been demonstrated that this system can be viewed as a vortical fluid which has remarkable similarities but also differences with classical ideal flows. In this respect, it was shown that the internal energy of the Pauli fluid can be interpreted, to some degree, as Fisher Information. In previous work on this subject, electromagnetic fields which are represented by a vector potential were ignored, here we remove this limitation and study the system under general electromagnetic interaction.

Many applications of superconductivity involve the interaction between superconductor coils and magnet or magnetic field. The electromagnetic interaction behavior between a superconducting coil and magnet or magnetic field is essentially different from that between a conventional conductor and magnet. The theory of electromagnetic interaction between superconductor and magnetic field remains to be fully developed. In this study, we carried out a series of experiments to investigate the characteristics of the interaction between HTS coils and permanent magnets. Five groups of tests with different configurations, including different sizes of the magnet, different turns of superconductor coil, different moving speeds and moving patterns of magnet, and different joint resistances of superconductor coil, were carried out. In this paper, we introduce the details and results of these experiments. Detailed analysis and discussions are also presented. The experimental results from this work may be helpful to understand the electromagnetic interaction between superconductor, in particular type II superconductor, and magnetic field.

This article focuses on modelling and validating a groundbreaking magnetorheological braking system. Addressing shortcomings in traditional automotive friction brake systems, including response delays, wear, and added mass from auxiliary components, the study employs a novel brake design combining mechanical and electrical elements for enhanced efficiency. Utilizing magnetorheological (MR) technology within a motor–brake system, the investigation explores the influence of external magnetic flux from the nearby motor on MR fluid movement, particularly under high-flux conditions. The evaluation of a high-magnetic-field mitigator is guided by simulated findings with the objective of resolving potential issues. An alternative method of resolving an interaction between an electric motor and a magnetorheological brake is presented. In addition, to test four configurations, multiple absorber materials are reviewed.

Plates of AL6XN super-austenitic stainless steel with a single-V groove preparation were gas metal arc welded (GMAW) with and without electromagnetic interaction of low intensity (EMILI) during welding using an ER-NiCrMo3 filler wire and 97% Ar + 3% N 2 as shielding gas. The fatigue behavior of the welded joints was evaluated under constant stress amplitude (Δσ/2) between 135 and 170 MPa ( R  = 0.1) and uniaxial load. The Wöhler diagram indicated that for stress amplitude of 170 MPa, 4.19 × 10 5 and 2.96 × 10 5  cycles were required for failure without and with EMILI, respectively, whereas for 135, 140, and 145 MPa, 1 × 10 7  cycles were reached without failure. Welding with EMILI was found to have a positive effect nearby fatigue limit. Observation of the fractures indicates that failures started on the surface of the specimens in the weld metal (WM) due to the stress concentration induced by the abundant presence of precipitates located along the interdendritic spaces in this zone of the welded joint. These particles acted as crack-nucleating agents and then the crack propagated throughout the WM. Fractography revealed brittle fracture associated to cleavage.

Ultralight axion-like particles are well-motivated dark matter candidates, naturally emerging from theories of physics at ultrahigh energies. Here we report the results of a direct search for electromagnetic interactions of axion-like dark matter in the mass range that spans three decades from 12 peV to 12 neV. The detection scheme is based on a modification of Maxwell’s equations in the presence of axion-like dark matter that mixes with a static magnetic field to produce an oscillating magnetic field. The experiment makes use of toroidal magnets with ferromagnetic powder cores made of an iron–nickel alloy, which enhance the static magnetic field by a factor of 24. Using superconducting quantum interference devices, we achieve magnetic sensitivity of 150 aTHz−1/2, which is at the level of the most sensitive magnetic field measurements demonstrated with any broadband sensor. We recorded 41 h of data and improved the best limits on the magnitude of electromagnetic coupling constant for axion-like dark matter over a part of our mass range, at 20 peV reaching 4.0 × 10−11 GeV−1 (95% confidence level). Our measurements begin to explore the coupling strengths and masses of axion-like particles, where their mixing with photons could explain the anomalous transparency of the Universe to TeV γ-rays.The presence of axion-like dark matter candidates is expected to induce an oscillating magnetic field, enhanced by a ferromagnet. Limits on the electromagnetic coupling strength of axion-like particles are reported over a mass range spanning three decades.

The measurement of the luminosity recorded by the CMS detector installed at LHC interaction point 5, using proton–proton collisions at s=13TeV in 2015 and 2016, is reported. The absolute luminosity scale is measured for individual bunch crossings using beam-separation scans (the van der Meer method), with a relative precision of 1.3 and 1.0% in 2015 and 2016, respectively. The dominant sources of uncertainty are related to residual differences between the measured beam positions and the ones provided by the operational settings of the LHC magnets, the factorizability of the proton bunch spatial density functions in the coordinates transverse to the beam direction, and the modeling of the effect of electromagnetic interactions among protons in the colliding bunches. When applying the van der Meer calibration to the entire run periods, the integrated luminosities when CMS was fully operational are 2.27 and 36.3 fb-1 in 2015 and 2016, with a relative precision of 1.6 and 1.2%, respectively. These are among the most precise luminosity measurements at bunched-beam hadron colliders.