E-field Research Articles

The use of interdisciplinary relations during the formation of the “Electric field vector” concept

The use of interdisciplinary relations during the formation of the “Electric field vector” concept

Ultrashort pulsed neutron source driven by two counter-propagating laser pulses interacting with ultra-thin foil

Neutron production via D(d, n)<sup>3</sup>He nuclear reaction during the interaction of two counter-propagating circularly polarized laser pulses with ultra-thin deuterium target is investigated by particle-in-cell simulation and Monte Carlo method. It is found that the rotation direction and initial relative phase difference of laser electric field vector have important effects on deuterium foil compression and neutron characteristics. The reason is attributed to the net light pressure and the difference in transverse instability development. The highest neutron yield can be obtained by choosing two laser pulses with a relative phase difference of 0 and the same rotation direction of the electric field vector. When the relative phase difference is 0.5π or 1.5π and the rotation direction of electric field vector is different, the neutrons have a directional spatial distribution and the neutron yield only slightly decreases. For left-handed circularly polarized laser pulse and right-handed circularly polarized laser pulse, each with an intensity of 1.23 × 10<sup>21</sup> W/cm<sup>2</sup>, a pulse width of 33 fs and a relative phase difference of 0.5π, it is possible to produce a pulsed neutron source with a yield of 8.5 × 10<sup>4</sup> n, production rate of 1.2 × 10<sup>19</sup> n/s, pulse width of 23 fs and good forward direction as well as tunable spatial distribution. Comparing with photonuclear neutron source and beam target neutron source driven by ultraintense laser pulses, the duration of neutron source in our scheme decreases significantly, thereby possessing many potential applications such as neutron nuclear data measurement. Our scheme offers a possible method to obtain a compact neutron source with short pulse width, high production rate and good forward direction.

Merging of Dirac points through uniaxial modulation on an optical lattice

We analyze the scenario of modulating the potential strength of bound atoms in an optical honeycomb lattice patterned by an electric field to emulate uniaxial strain. This modulation can be achieved by a combination of the strength of the patterned electric field and gauge vector effects using the Floquet approach. We show that such a modulation allows one to follow through a topological transition between a semi-metal and a band insulator, when two non-equivalent K points merge as a function of the electric field strength. We explicitly compute the wavefunctions for the moving K points and the Chern numbers up to the transition. Anisotropic effective masses and the insulating gap are described close to the semimetal-insulator transition.

Thin layers of microwave absorbing metamaterials with carbon fibers and FeSi alloy ribbons to enhance the absorption properties

In order to break through the bottleneck of narrow effective absorption bandwidth (reflection loss RL ≤ −10 dB) of microwave absorbing materials, herein, we fabricate the metamaterials with carbon fiber (CF) and FeSi alloy (FSA) ribbon metastructure which is distributed in the carbonyl iron powders (CIP)/polyurethane (PU) matrix. The experimental results show that the microwave absorption capacity of the matrix can be significantly enhanced by CF. Compared with the pure matrix, the effective absorption bandwidth increases from 9.4–13.44 GHz to 11–16.8 GHz when the CF is parallel to the electric field vector and the spacing between adjacent CF is 20 mm. Furthermore, the CF and FSA ribbons are arranged in the matrix as an orthogonal arrangement, and the best absorption bandwidth cover 9.76–14.46 GHz when the electric field is parallel and 9.96–14.1GHz when the electric field is vertical when the spacing is 30 mm. The electromagnetic simulation of the metamaterials is calculated, it is proved that the increase of effective absorption bandwidth is due to the strengthening of carbon fiber and its coupling with FSA ribbon. This paper provides a new research path for improving the absorption properties of thin layer microwave absorbing materials.

Néel-type optical target skyrmions inherited from evanescent electromagnetic fields with rotational symmetry.

Optical skyrmions have recently attracted growing interest due to their potential applications in deep-subwavelength imaging and nanometrology. While optical skyrmions have been successfully demonstrated using different field vectors, the study of their generation and control, as well as their general correlation with electromagnetic (EM) fields, is still in its infancy. Here, we theoretically propose that evanescent transverse-magnetic-polarized (TM-polarized) EM fields with rotational symmetry are actually Néel-type optical target skyrmions of the electric field vectors. Such optical target skyrmions are independent of the operation frequency and medium. Our proposal was verified by numerical simulations and real-space nano-imaging experiments performed on a graphene monolayer, where the target skyrmions could be as small as ∼100 nm in diameter. The results can therefore not only further our understanding of the formation mechanisms of EM topological textures, but also provide guidelines for the facile construction of EM skyrmions that may impact future information technologies.

REARRANGEMENTS IN THE CONFORMATIONAL STRUCTURE OF POLYELECTROLYTES ON THE SURFACE OF A FLATTENED METAL NANOSPHEROID IN AN ALTERNATING ELECTRIC FIELD

A mathematical model has been presented for the formation of the conformational structure of chain units in a polyelectrolyte adsorbed on a flattened conducting charged nanospheroid polarized in an external electric field, which harmonically varies at a frequency much lower than the plasma frequency of the nanospheroid metal. Molecular dynamics has been employed to study the rearrangements in the conformational structure of uniformly charged polypeptides adsorbed on the surface of the oppositely charged flattened gold nanospheroid in an external alternating electric field, the strength vector of which varies along the rotation axis of the nanospheroid. One-dimensional density distributions along the rotation axis, as well as radial distributions, have been plotted for atoms of the polypeptides adsorbed on the nanospheroid surface. At a low temperature, a narrow ring-shaped polyelectrolyte fringe is formed in the equatorial region of the flattened metal nanospheroid, and the fringe density increases with the total charge of the nanospheroid and the number of charged units in polyelectrolyte macrochains. At a high temperature, the formed narrow macromolecular ring periodically shifts along the rotation axis of the nanospheroid with redirections of the polarizing electric field vector. The amplitude of the shifts increases with a decrease in the total charge of the nanospheroid and an increase in the fraction of charged units in a polyelectrolyte.

The C-eigenvalue of third order tensors and its application in crystals

<p style="text-indent:20px;">In crystallography, piezoelectric tensors of various crystals play a crucial role in piezoelectric effect and converse piezoelectric effect. Generally, a third order real tensor is called a piezoelectric-type tensor if it is partially symmetric with respect to its last two indices. The piezoelectric tensor is a piezoelectric-type tensor of dimension three. We introduce C-eigenvalues and C-eigenvectors for piezoelectric-type tensors. Here, "C'' names after Curie brothers, who first discovered the piezoelectric effect. We show that C-eigenvalues always exist, they are invariant under orthogonal transformations, and for a piezoelectric-type tensor, the largest C-eigenvalue and its C-eigenvectors form the best rank-one piezoelectric-type approximation of that tensor. This means that for the piezoelectric tensor, its largest C-eigenvalue determines the highest piezoelectric coupling constant. We further show that for the piezoelectric tensor, the largest C-eigenvalue corresponds to the electric displacement vector with the largest 2-norm in the piezoelectric effect under unit uniaxial stress, and the strain tensor with the largest 2-norm in the converse piezoelectric effect under unit electric field vector. Thus, C-eigenvalues and C-eigenvectors have concrete physical meanings in piezoelectric effect and converse piezoelectric effect. Finally, by numerical experiments, we report C-eigenvalues and associated C-eigenvectors for piezoelectric tensors corresponding to several piezoelectric crystals.</p>

Combined effects of the lewis acidity and electric field of proximal redox innocent metal ions on the redox potential of vanadyl Schiff base complexes: an experimental and theoretical study.

The reactivity of biological or synthetic metalloenzymes is modulated in the presence of redox innocent Lewis acidic metal ions as they change the redox potential of the redox active metal ions present in the active site of metalloenzymes. To study this effect, we synthesised a mono-nuclear V(IV) complex (VOL, 1) with an N2O4 donor bicompartmental ligand, characterized it by single-crystal X-ray crystallography and recorded its cyclic voltammogram in acetonitrile. The CV revealed a reversible redox process for the V(IV)/V(V) couple. The potential of the V(IV)/V(V) couple shifted to a more positive value when equivalent amounts of Li+, Na+, K+, Mg2+, Ca2+ and Ba2+ ions were added separately to its acetonitrile solution, but the extent of shift for Li+ and Mg2+ was much less than that of the other metal ions. The guest metal ions except Li+ and Mg2+ were accommodated in the outer compartment of VOL as confirmed by IR and UV-Vis spectral analysis. Single-crystal structural analysis of [(VOL)KPF6]2, (1·K) and [(VOL)Ba(ClO4)2(H2O)]n, (1·Ba) also confirmed the hetero-metallic adduct formation. The correlation of the shift of the V(IV/V) redox potential with the Lewis acidity of respective metal ions deviated appreciably from linearity. DFT calculations suggest that the shift in potential is probably controlled by local electric fields induced by those ions, as indicated by 2D vector electric field maps.

Dual Angular Tunability of 2D Ge/ZnSe Notch Filters: Analysis, Experiments, Physics

Abstract2D resonant gratings enable dual angular tunability by controlling the plane of incidence (POI) under linear polarization. If the POI is set to be perpendicular to the electric field vector (s‐polarization or transverse electric (TE) polarization), an excited TE mode provides spectral tuning. The orthogonally propagating transverse magnetic (TM) mode is robust in angle. Conversely, if the POI is set for p‐polarization, an excited TM mode provides the tuning. Detailed explanations of the underlying physical processes are set forth by decomposing the 2D lattice into equivalent 1D gratings using second‐order effective‐medium theory. This is shown to work extremely well even for a strongly modulated lattice with refractive‐index contrast of 3. With proper design and corresponding experiments, a widely tunable notch filter covering long‐wave infrared bands is demonstrated. Experimentally varying the incidence angle up to 16° under p‐polarization, a notch channel in TM mode tunes across a band exceeding 0.5 µm with the TE channel remaining at a constant wavelength. The interesting appearance of a resonance channel originating in diagonally propagating leaky modes is briefly examined. The analysis and experiments presented can be useful for realizing diverse 2D tunable filters while furnishing methodology for detailed understanding of the attendant near fields and mode structure.

Swarm Thermal Ion Imager measurement performance

We assess the performance of the thermal ion imaging (TII) technique as conceived for the Swarm Earth Explorer satellites. Analysis, simulation, and laboratory testing performed prior to flight provided estimates of systematic and random error sources of the electric field instrument’s vector ion drift, electric field, and ion kinetic temperature measurements. An end-to-end instrument simulator, consisting of models of the TIIs on a prototypical Swarm satellite orbiting Earth with ionospheric plasma, electric field, and magnetic field inputs, was used to generate TII sensor data (level 0 instrument data). These data were processed with a prototype processor (the level 1b processor) to characterize theoretical measurement performance. We describe the methodology used to assess TII measurement uncertainty and present the main findings of the end-to-end measurement performance study. In addition, we assess the measurement performance achieved during approximately eight years of orbital operations. Example measurements demonstrate the quality of ion drift velocity. Unprocessed TII imagery reveals spurious signals which can affect measurement performance. Availability of such imagery has proven vital for diagnosing measurement anomalies associated with sensor operation and spacecraft–plasma interactions.Graphical

A General ADE-WLP-FDTD Method With a New Temporal Basis for Wave Propagation

Based on an auxiliary differential equation (ADE) and a new temporal basis function, we propose a 3-D ADE finite-difference time-domain method (FDTD) with weighted Laguerre polynomials (WLPs), 3-D ADE-WLP-FDTD for short, to calculate wave propagation in general dispersive materials. Our proposed method introduces a linear combination of three WLPs as a temporal basis to improve computational efficiency and reduce memory usage. The ADE technique, which can effectively model dispersive media, was used to establish the relationship between the electric displacement vector and electric field intensity. Two numerical examples were presented to validate the advantages of the proposed approach. The simulation results reveal that compared with the conventional ADE-WLP-FDTD method, the proposed method can speed up the computational process and reduce memory usage with comparable accuracy.

Wave vector and field vector orientation dependence of Fe K pre-edge X-ray absorption features in clinopyroxenes

Abstract Pre-edge X-ray absorption features are commonly used to derive redox states for transition metal oxides in crystals and glasses. Several calibrations for Fe2+ and Fe3+ in silicate glasses have utilized the general relationships among pre-edge peak intensity, energy, and redox state. However, absorption variations complicate those relationships in anisotropic crystals. Although absorption anisotropy at and above the energy of the rising edge adheres to the typical cos2 relationship observed in absorption spectroscopies at other energies, the anisotropy of the pre-edge is far more complicated. Prior studies focusing on pre-edge absorption anisotropy demonstrate a 1-cos4φ dependence of absorption magnitudes with rotation. Experiments presented here show that absorption magnitudes of the pre-edge vary as a function of both electric field vector orientation and wave vector direction. However, rotations around the field vector axis or wave vector axis individually result in cos2 dependence of absorption magnitudes. Rotations where both wave vector and field vector orientation are varied are not well fit by either model in the pre-edge. The resulting anisotropy complicates the process of measuring characteristic absorption in the pre-edge, making valence state determinations challenging for strongly anisotropic crystal structures such as pyroxene.

A parallel adaptive finite-element approach for 3-D realistic controlled-source electromagnetic problems using hierarchical tetrahedral grids

SUMMARY To effectively and efficiently interpret or invert controlled-source electromagnetic (CSEM) data which are recorded in areas with the kind of complex geological environments and arbitrary topography that are typical, 3-D CSEM forward modelling software that can quickly solve large-scale problems, provide accurate electromagnetic responses for complex geo-electrical models and can be easily incorporated into inversion algorithms are required. We have developed a parallel goal-oriented adaptive mesh refinement finite-element approach for frequency-domain 3-D CSEM forward modelling with hierarchical tetrahedral grids that can offer accurate electromagnetic responses for large-scale complex models and that can efficiently serve for inversion. The approach uses the goal-oriented adaptive vector finite element method to solve the total electric field vector equation. The geo-electrical model is discretized by unstructured tetrahedral grids which can deal with complex underground geological models with arbitrary surface topography. Different from previous adaptive finite element software working on unstructured tetrahedral grids, we have utilized a novel mesh refinement technique named the longest edge bisection method to generate hierarchically refined grids. As the refined grids are nested into the coarse grids, the refinement technique can precisely map the electrical parameters of inversion grids onto the forward modelling grids so that the extra numerical errors generated by the inconsistency of electrical parameters between inversion grids and forward modelling grids are eliminated. In addition, we use the parallel domain-decomposition technique to further accelerate the computations, and the flexible generalized minimum residual solver (FGMRES) with an auxiliary Maxwell solver pre-conditioner to solve the final large-scale system of linear equations. In the end, we validate the performance of the proposed scheme using two synthetic models and one realistic model. We demonstrate that accurate electromagnetic fields can be obtained by comparison with the analytic solutions and that the code is highly scalable for large-scale problems with millions or even hundreds of millions of unknowns. For the synthetic 3-D model and the realistic model with complex geometry, our solutions match well with the results calculated by an existing 3-D CSEM forward modelling code. Both synthetic and realistic examples demonstrate that our newly developed code is an effective, efficient forward modelling engine for interpreting CSEM field data acquired in areas of complex geology and topography.

Nanoparticle Shape Optimization for Tamm-Plasmon-Polariton-Based Organic Solar Cells in the Visible Spectral Range

The effect of the shape of the nanoparticles and the polarization of incident light on the surface current density and the efficiency of an organic solar cell based on the Tamm plasmon polariton is investigated. In the cases of both elongated and flattened nanoparticles, it is shown that the efficiency of such a solar cell is increased when the electric field vector is parallel to the largest axis of the spheroid.

Direct Synthesis and Design of Wideband Linear-to-Circular Polarizers on 3-D Frequency Selective Structures

A novel direct synthesis method for wideband linear-to-circular polarizers on 3-D frequency selective structures is presented. The proposed linear-to-circular polarizer consists of two orthogonal linearly polarized (LP) transmission paths, both of which are comprised by three cascaded sections of slotline structures. Under the incidence of an LP wave with its electric-field ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula> -field) vector of a titled angle 45°, each path can achieve a transmission passband for one of the two orthogonal components decomposed by the incident <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula> -field vector. To obtain a transmitted wave with circularly polarized (CP) property, the well-known conditions on magnitude and phase difference of these two paths are presented. Then, to develop a unified synthesis method, two new conditions of phase difference and phase slope at the center frequency are introduced to replace the typical phase condition. The closed-form equations are derived, and a synthesis procedure is given. It can be obtained that all the involved circuit parameters can be derived from the specifications of these two paths, such as in-band insertion loss (IL) ripples and fractional bandwidths. Moreover, the phase difference condition of these two paths is further modified to obtain an arbitrary axial ratio (AR) at the center frequency and enhance the AR bandwidth of the polarizer. A group of design examples are theoretically investigated to demonstrate and verify the design concept. An alternative design example is finally selected and fabricated. Good agreement between simulated and measured results features its advantages of wide AR bandwidth and low IL. Therefore, the proposed synthesis method can provide a promising solution to design many other types of wideband linear-to-circular polarizers.

THE NOTES ON ENERGY AND ELECTROMAGNETIC FIELD VECTORS IN THE NULL CONE Q2

In this paper, we characterize the directional derivatives in accordance with the asymptotic orthonormal frame {x,α,y} in Q^2. Also, we express the extended Serret-Frenet relations by using cone Frenet formulas and we explain the geometrical understanding of energy on each asymptotic orthonormal vector fields in null cone. Furthermore, we express the bending elastic energy function for the same particle according to curve x(s,ξ,η) and we finalize our results by providing energy variation sketches according to directional derivatives for different cases. Additionally, we explain a geometrical interpretation of the energy for unit vector fields and we express Maxwell’s equations for the electric and magnetic field vectors in null cone 3-space.

Scattering analysis of two-dimensional Airy beams by typical non-spherical particles.

The scattering of structured light beams by various particles is an important subject of research with myriad practical applications, such as the manipulation, measurement, and diagnosis of small particles. We carry out an analysis of the scattering of two-dimensional (2D) Airy beams by typical non-spherical particles. The electric and magnetic field vectors of the incident Airy beams are derived by introducing a vector potential in the Lorenz gauge. The scattered fields of the particles are obtained by utilizing the method of moments based on surface integral equations. Some numerical simulations for the scattering of 2D Airy beams by several selected non-spherical particles are performed and analyzed. Especially, a spheroidal particle is taken as an example, and the effects of various parameters describing the 2D Airy beams on its differential scattering cross section are examined. It is expected that this work will be helpful for understanding the interactions of 2D Airy beams with non-spherical particles and their further applications.

Electric fields control water-gated proton transfer in cytochrome c oxidase

Aerobic life is powered by membrane-bound enzymes that catalyze the transfer of electrons to oxygen and protons across a biological membrane. Cytochrome c oxidase (CcO) functions as a terminal electron acceptor in mitochondrial and bacterial respiratory chains, driving cellular respiration and transducing the free energy from O2 reduction into proton pumping. Here we show that CcO creates orientated electric fields around a nonpolar cavity next to the active site, establishing a molecular switch that directs the protons along distinct pathways. By combining large-scale quantum chemical density functional theory (DFT) calculations with hybrid quantum mechanics/molecular mechanics (QM/MM) simulations and atomistic molecular dynamics (MD) explorations, we find that reduction of the electron donor, heme a, leads to dissociation of an arginine (Arg438)-heme a3 D-propionate ion-pair. This ion-pair dissociation creates a strong electric field of up to 1 V Å-1 along a water-mediated proton array leading to a transient proton loading site (PLS) near the active site. Protonation of the PLS triggers the reduction of the active site, which in turn aligns the electric field vectors along a second, "chemical," proton pathway. We find a linear energy relationship of the proton transfer barrier with the electric field strength that explains the effectivity of the gating process. Our mechanism shows distinct similarities to principles also found in other energy-converting enzymes, suggesting that orientated electric fields generally control enzyme catalysis.

The seasonal variation in the polarization (E x /E y ) of the characteristic wave in ionosphere plasma

Abstract Light is a well-known electromagnetic wave that propagates, transmits, reflects, and polarizes in any medium. Waves have a huge technical impact as a determinant of human life because of their qualities. Using real geometrical Earth’s magnetic field, this article investigates the latitude and seasonal fluctuation of polarization magnitude of a polarized characteristic wave (no electric flux in the wave’s propagation direction) in the ionospheric plasma (the examined conditions). Both the volume polarization and wave polarization have been solved analytically in the ionospheric plasma, taking into account the accepted parameters. Furthermore, the volume and wave polarization were mathematically proven to be connected, and numerical wave polarization values were produced in the ionospheric plasma under the considered parameters. When a magnetic field operates on a medium, it causes the medium to become anisotropic. The wave polarization is ecliptic and the electric field vector does not sweep a circle as understood from analytical solutions when the Earth’s magnetic field and particle collisions are taken into account. There is a real and an imaginary element to the wave’s electric field ratio (E x /E y = a + ib). The real and imaginary parts of wave polarization in the x and y planes form the shape of the elliptic structure, and the real component is associated with advancing, while the imaginary part is related to attentiveness. The ionosphere of Earth, all physical parameters, such as refractive index, dielectric structure, and conductivity, have a complicated structure. According to the study, the real part of the polarization of the characteristic wave is related to the absorption coefficient and the imaginary part is proportional to the refractive index of the medium.

Jet Effusion from a Metal Droplet Irradiated by a Polarized Ultrashort Laser Pulse

Fragmentation of liquid-metal droplets irradiated by linearly and circularly polarized femtosecond laser pulses is observed in our experiment. The obtained shadowgraph snapshots demonstrate that a circularly polarized pulse may produce several randomly oriented jets effused from the expanding droplets, while a linearly polarized laser pulse generates strictly the cruciform jets. The latter orientation is tied with polarization plane, rotation of which causes rotation of the cruciform jets by the same angle. To shed light on the experimental data we perform molecular dynamics simulation of droplet expansion induced by angle-dependent heating. Our simulation shows that the jet directions are determined by an oriented angle-dependent energy distribution within a frontal hemisphere layer of droplet after absorption of linearly polarized light. As a result, the produced flow velocity field guided by surface tension forms two high-speed opposite jets oriented across the electric field vector as in our experiment. A shock-wave pulse generated in the frontal layer has angle-dependent amplitude inherited from the oriented energy deposition. The release part of shock pulse produces a cavitation zone nearby the droplet center, and thus an expanding spherical shell is formed from the droplet. The flow velocities within a rearside hemisphere of the shell, produced after reflection of the shock wave from the rear side of droplet, generate two low-speed opposite jets oriented along the electric field vector. Thus we find that the cruciform jets are originated independently from the frontal and rear sides of droplet, and a pair of frontal jets is faster than a pair of rearside jets.