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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.

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.

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.

An atom in open space can be detected by means of resonant absorption and reemission of electromagnetic waves, known as resonance fluorescence, which is a fundamental phenomenon of quantum optics. We report on the observation of scattering of propagating waves by a single artificial atom. The behavior of the artificial atom, a superconducting macroscopic two-level system, is in a quantitative agreement with the predictions of quantum optics for a pointlike scatterer interacting with the electromagnetic field in one-dimensional open space. The strong atom-field interaction as revealed in a high degree of extinction of propagating waves will allow applications of controllable artificial atoms in quantum optics and photonics.

Multiple optical harmonic generation—the multiplication of photon energy as a result of nonlinear interaction between light and matter—is a key technology in modern electronics and optoelectronics, because it allows the conversion of optical or electronic signals into signals with much higher frequency, and the generation of frequency combs. Owing to the unique electronic band structure of graphene, which features massless Dirac fermions 1 – 3 , it has been repeatedly predicted that optical harmonic generation in graphene should be particularly efficient at the technologically important terahertz frequencies 4 – 6 . However, these predictions have yet to be confirmed experimentally under technologically relevant operation conditions. Here we report the generation of terahertz harmonics up to the seventh order in single-layer graphene at room temperature and under ambient conditions, driven by terahertz fields of only tens of kilovolts per centimetre, and with field conversion efficiencies in excess of 10 −3 , 10 −4 and 10 −5 for the third, fifth and seventh terahertz harmonics, respectively. These conversion efficiencies are remarkably high, given that the electromagnetic interaction occurs in a single atomic layer. The key to such extremely efficient generation of terahertz high harmonics in graphene is the collective thermal response of its background Dirac electrons to the driving terahertz fields. The terahertz harmonics, generated via hot Dirac fermion dynamics, were observed directly in the time domain as electromagnetic field oscillations at these newly synthesized higher frequencies. The effective nonlinear optical coefficients of graphene for the third, fifth and seventh harmonics exceed the respective nonlinear coefficients of typical solids by 7–18 orders of magnitude 7 – 9 . Our results provide a direct pathway to highly efficient terahertz frequency synthesis using the present generation of graphene electronics, which operate at much lower fundamental frequencies of only a few hundreds of gigahertz. Efficient terahertz harmonic generation—challenging but important for ultrahigh-speed optoelectronic technologies—is demonstrated in graphene through a nonlinear process that could potentially be generalized to other materials.