Transverse Electric Field Components Research Articles

Atmospheric pressure uniform dielectric barrier discharge (DBD) in a wide air gap initiated from a narrow starting point

Generating a uniform non-equilibrium plasma in atmospheric pressure air has always been a challenge. It is believed that the maximum spacing for generating a uniform non-equilibrium plasma in atmospheric pressure air, whether using AC or nanosecond pulse drive, is 4 mm. Discharges are always non-uniform when the spacing is greater than 4 mm. In this paper, we propose a new type of dielectric barrier discharge structure to address this challenge. The left end of the structure rapidly increases the discharge spacing from 0.5 mm to 6 mm, while the right side of the main discharge gap maintains a uniform spacing of 6 mm. Nanosecond pulse voltage is used to drive the plasma, an ICCD camera is used to capture the image of the plasma during a discharge pulse cycle, which indicates that a uniform plasma within the 6 mm spacing of the main discharge gap is generated. Upon further reducing the ICCD camera’s exposure time to 20 ns, it is revealed that the uniform plasma is formed due to the rapid propagation of the plasma from left to right at a speed of order of 105 m s−1. Due to the small transverse component of the external electric field, this rapid propagation behavior cannot be due to the external electric field. Therefore, this paper further proposes the hypothesis of electric dipole formation leading to this fast propagation. The hypothesis suggests that the charge separation on the surface of the anode forms an electric dipole, which generates a local discharge at its right end. This local discharge further triggers the discharge in the main gap, and the main gap discharge, in turn, forms a dipole due to charge separation again, by repeating this cycle, the plasma propagates rapidly to the right. Further analysis demonstrates that this dipole can indeed produce a strong electric field of up to 41 kV cm−1 at its right end, which is sufficient to induce a local discharge. Moreover, under such a strong electric field, the electron migration rate can indeed reach 105 m s−1. These findings support the plausibility of this hypothesis.

Vectorial characterization of surface wave via one-dimensional photonic-atomic structure

Quantitative assessment of polarization properties of waves opens up the way for effective exploitation of them in many amazing applications. Tamm surface waves (TSW) that propagate on the interface of periodic dielectric media are proposed for many applications in numerous reports. The polarization state of TSW is not simply intuitive and would not be extracted from reflection spectra. Here considering orientation sensitive nature of the interaction between polarized electromagnetic wave and atom, we try to quantitatively characterize the polarization state of TSWs, excited on the surface of the 1D photonic crystal. To do this we performed direct contact between TSW and rubidium atomic gas by fabrication of a one-dimensional photonic crystal-atomic vapor cell and applied a moderate external magnetic field to create geometrical meaning and a sense of directionality to dark lines in reflection intensity. Our experimental results indicate that transition lines in the reflection spectrum of our hybrid system modify dependent on the orientation of the applied magnetic field and the transverse spin of TSW. We have used these changes to redefine the geometry of Voigt and Faraday for evanescent waves, especially Tamm surface waves. In the end, we performed simple mathematical operations on absorption spectra and extract the ratio of longitudinal and transverse electric field components of the polarization vector of TSW equal to 25\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\frac{2}{5}$$\\end{document}.

Control over polarization of vertically emitting random lasers based on dye doped nematic liquid crystals by applying a transverse electric field locally

Flexible control over random lasers (RLs) is highly desired. In this manuscript, a control over the polarization of random lasing emitted vertically from dye doped nematic liquid crystal (NLC) cell by the transverse component of a local ac electric field was demonstrated. The polarizing direction of the RL could be tuned continuously and monotonously with the increase of the field strength, from the direction along the NLC director without an applied electric field. The maximum rotation angle of the polarizing direction reached nearly 90° at the applied voltage of 200 V (root-mean-square value) across the 230 μm wide slit. The degree of polarization declined from 1 at zero voltage, and after reaching the minimum rose with the field strength. The lasing spectrum consists of sharp spikes corresponding to the resonant modes for all the applied voltages. The mechanisms responsible for electrically tuning the polarization of the RL were discussed. Optimizing the voltage characteristic of the polarization tunability was suggested by the preliminary experimental results.

Structured Vector Field Manipulation of Terahertz Wave along the Propagation Direction Based on Dielectric Metasurfaces

AbstractThe generation and manipulation of vector light fields are of great significance for both fundamental research and industrial applications of polarized optics. In recent years, the spatial domain control of structured vector fields has gradually expanded from two‐ to three‐dimensional, including traditional optics and meta‐optics. Here, a new method to generate and manipulate structured vector light fields along the propagation direction is proposed, and the functionality in terahertz band using all‐silicon metasurfaces is demonstrated. The coherent superposition of orthogonal circularly polarized terahertz waves through long focal depth and multifocal metalens is completed, and varying phase differences between them in the propagation direction via path accumulation or initial phase design are introduced, thereby continuous variation or independently designed vector polarization distributions in multiple planes are obtained. It is worth mentioning that the proposed scheme is not only for the design of transverse electric field components, but also shows a strong ability for manipulation of the longitudinal component. This scheme realizes the polarization distribution designs of three‐dimensional vector fields in three‐dimensional space, and provides a new inspiration for the generation and manipulation of vector beams based on meta‐optics.

Analysis and Design of Bessel Beam Launchers: Transverse Polarization

In this communication, we present a theoretical analysis, design, and fabrication of a limited-diffractive planar Bessel beam launcher, that exhibits a zeroth-order Bessel profile in the transverse electric field component with respect to the z-propagation axis. The launcher is designed by synthesizing a finite zeroth-order, first kind Hankel aperture distribution, polarized along a fixed polarization unit vector. The field radiated by such an aperture distribution is derived by following an approximate model based on the geometric theory of diffraction, thus allowing to highlight the relevant wave constituents involved in transverse Bessel beam generation, also including the effect of aperture truncation on the radiated beam. Moreover, the theoretical analysis has been profitably applied to the design of a circular-polarized planar transverse Bessel beam launcher by means of a slotted radial waveguide. A prototype of right-handed circular polarized (RHCP) transverse Bessel beam launcher has then been fabricated at f = 30 GHz. The measured transverse electric field component shows a satisfactory agreement with full-wave numerical simulations.

A blue phase liquid crystal Fresnel lens with large transverse electric field component

ABSTRACT A Fresnel lens with blue phase liquid crystal (BPLC) material is proposed, and the mainly electrical field in BPLC layer is parallel to substrates. The structure and proportion of the applied voltage on every Fresnel zones is constant, through adjusting the voltage applied on the edges of Fresnel zones, the focal length can be tuned. Moreover, by increasing the number of the identical Fresnel zones of the BPLC lens, a BPLC lens with a larger aperture can be easily obtained, and the light control power is also high while maintaining a fast response time and a thin BPLC layer.

Role of scattering and birefringence in phase retardation revealed by locus of Stokes vector on Poincaré sphere.

.Significance: Biological tissues are typically characterized by high anisotropic scattering and may also exhibit linear form birefringence. Both scattering and birefringence bias the phase shift between transverse electric field components of polarized light. These phase alterations are associated with particular structural malformations in the tissue. In fact, the majority of polarization-based techniques are unable to distinguish the nature of the phase shift induced by birefringence or scattering of light.Aim: We explore the distinct contributions of scattering and birefringence in the phase retardation of circularly polarized light propagated in turbid tissue-like scattering medium.Approach: The circularly polarized light in frame of Stokes polarimetry approach is used for the screening of biotissue phantoms and chicken skin samples. The change of optical properties in chicken skin is accomplished by optical clearing, which reduces scattering, and mechanical stretch, which induces birefringence. The change of optical properties of skin tissue is confirmed by spectrophotometric measurements and second-harmonic generation imaging.Results: The contributions of scattering and birefringence in the phase retardation of circularly polarized light propagated in biological tissues are distinguished by the locus of the Stokes vector mapped on the Poincaré sphere. The phase retardation of circularly polarized light due to scattering alterations is assessed. The value of birefringence in chicken skin is estimated as , which agrees with alternative studies. The change of birefringence of skin tissue due to mechanical stretch in the order of is detected.Conclusions: While the polarimetric parameters on their own do not allow distinguishing the contributions of scattering and birefringence, the resultant Stokes vector trajectory on the Poincaré sphere reveals the role of scattering and birefringence in the total phase retardation. The described approach, applied independently or in combination with Mueller polarimetry, can be beneficial for the advanced characterization of various types of malformations within biological tissues.

Multipolar, polarization-shaped high-order harmonic generation by intense vector beams

High harmonic generation (HHG) is a manifestation of the strongly nonlinear response of matter to intense laser fields and has, as the basis for coherent XUV sources a variety of applications. Recently, HHG from atoms in a phase and polarization structured laser was demonstrated and interpreted based on the transverse electric field component of the driving pulse. Here we point out that as dictated by Maxwell equations, such fields have a longitudinal component which in general has a fundamental influence on the charge dynamics. For instance, its interplay with the transversal field component enables endowing the emitted radiation locally with circular polarization and a defined polarity. It is shown that the time-dependent Stokes parameters defining the polarization state of HHG can be tuned by varying the waist of the driving field which in turn, changes the ratio between the longitudinal and transverse electric-field components of the driving laser. In addition, employing a multipole expansion of the produced harmonics exposes the specific multipolar character and the relation to the spatial structure of the driving field polarization states. The scheme proposed here allows a full polarization control of the emitted harmonics by only one driving laser. A tighter focusing of the driving pulse renders possible the emission of harmonics with both even and odd spatial symmetry. The underlying mechanism is due to the fundamental interplay between the transverse and longitudinal components of the laser's electromagnetic vector potential. The ratio between those components is controllable by just focusing the laser spot, pointing to an accessible tool for polarization and polarity control of the high harmonics.

Towards polarization-based excitation tailoring for extended Raman spectroscopy.

Undoubtedly, Raman spectroscopy is one of the most elaborate spectroscopy tools in materials science, chemistry, medicine and optics. However, when it comes to the analysis of nanostructured specimens or individual sub-wavelength-sized systems, the access to Raman spectra resulting from different excitation schemes is usually very limited. For instance, the excitation with an electric field component oriented perpendicularly to the substrate plane is a difficult task. Conventionally, this can only be achieved by mechanically tilting the sample or by sophisticated sample preparation. Here, we propose a novel experimental method based on the utilization of polarization tailored light for Raman spectroscopy of individual nanostructures. As a proof of principle, we create three-dimensional electromagnetic field distributions at the nanoscale using tightly focused cylindrical vector beams impinging normally onto the specimen, hence keeping the traditional beam-path of commercial Raman systems. In order to demonstrate the convenience of this excitation scheme, we use a sub-wavelength diameter gallium-nitride nanostructure as a test platform and show experimentally that its Raman spectra depend sensitively on its location relative to the focal vector field. The observed Raman spectra can be attributed to the interaction with transverse and pure longitudinal electric field components. This novel technique may pave the way towards a characterization of Raman active nanosystems, granting direct access to growth-related parameters such as strain or defects in the material by using the full information of all Raman modes.

Tight-focusing properties of linearly polarized circular Airy Gaussian vortex beam

We show the tight-focusing properties of a linearly polarized circular Airy Gaussian vortex beam (CAiGVB) with a high-numerical-aperture objective lens; the light intensity distributions exhibit diversity with different positions of the vortex pairs (on-axis or off-axis vortex pairs). By choosing different optical distribution factors, the CAiGVB turns into a circular Airy vortex beam or Gaussian vortex beam, and the depth of focus can also be controlled. It is known that the vortex beam possesses both orbital and spin angular momentum. The spin density vector changes its direction in three-dimensional space during beam propagation, as long as it is not purely transverse or longitudinal, which would cause 3D polarization ellipse topologies. In contrast, the polarization topologies degenerate into 2D when the spin density vector is purely transverse or longitudinal. Furthermore, the direction of the spin density vector is closely related to the Gouy phase difference between longitudinal and transverse electric field components of the vectorial beam.

Slowly spreading propagation characteristics of flying electromagnetic toroid

As a new kind of electromagnetic pulses with finite energy, the flying electromagnetic toroid (FET), also called as the flying electromagnetic doughnut, has significant potential applications, such as the excitation of anapole non-radiation mode and the acceleration of charged particles. To show the propagation characteristic of FET, the spatial distribution and spectrum characteristic of the transverse and longitudinal components of FET and its topology evolution in the propagation process are discussed in this paper. Without loss of generality, we theoretically research the longitudinal field and transverse field of the transverse magnetic (TM) FET based on the real part of FET’s propagation equations. The field distribution, topology, and spectrum when the FET propagates to different positions can be calculated by assigning corresponding values to the time variable in FET’s propagation equations, therefore, the propagation characteristics of FET can be studied accurately in theory. The magnetic field of TM FET is distributed into rings in the plane vertical to the propagation direction and the electric field of TM FET is rotated around the magnetic field, which means the FET has a hypertorus topology. All the field components of FET are rotationally symmetric in the plane vertical to the propagation direction. The FET’s center is the maximum position of the longitudinal electric field component and the null position of the transverse electric and magnetic field components. Maximum values of FET’s longitudinal field are always located on the central line of FET’s propagation path and decrease gradually in the propagation process. Different from the longitudinal field, the maximum value of FET’s transverse field gradually moves away from FET’s center. The theoretical research indicates that the FET spreads quite slowly in its early propagation state and spreads linearly after propagating a long distance, which has the slowly spreading propagation characteristic even in the so-called focused range with stable toroidal topological structure. The further spectrum analysis shows that the high-frequency components spread less than the low-frequency components and the high-frequency components play a vital role in the topology retention of FET in the focused range, which may provide a basis for the generation and application of FET. At present, the theoretical research on FET’s characteristics is increasingly improved. To apply the attractive characteristics of FET in actual systems, it is necessary to actually generate FET. Therefore, the generation method of FET should become the next research emphasis.

Spatial autoresonance acceleration physical scheme based on magnetic rings system

The spatial auto-resonant acceleration scheme consists in the acceleration of an electrons beam by the transverse electric field component of a standing microwave field and an external inhomogeneous magnetostatic field, whose longitudinal profile is fitted to maintain the electron cyclotron resonance condition along of its helical trajectories. In practice, the external magnetic profile can be generated by a system of current coils. In order to save energy and the possibility to reduce space, we study the option to replace the coils by a magnetic rings system of uniform axial magnetization. In this work, we present both, the results of the magnetostatic field generated by a magnets system, which is calculated from the magnetization currents using the Biot-Savart law, and the acceleration of an electrons beam in the spatial auto-resonant acceleration regime employing said magnetostatic field. The electron trajectory, its velocity and energy are obtained from the numerical solution of the relativistic Newton-Lorentz equation, showing that is possible to accelerate electrons injected with energies about of some electronvolts to values about of 250 keV.

Effective light polarization insensitive and omnidirectional properties of Si nanowire arrays developed on different crystallographic planes

In this paper, fabrication of vertical Si nanowire arrays (SiNWAs) by a facile metal assisted chemical etching approach on different crystallographic planes of Si has been reported. A very low specular reflectance (Rspec) of 0.04% and 0.03% has been achieved in the whole visible range for SiNWAs grown on Si(100) and Si(111) oriented substrates, respectively. High broadband enhancement has been detected for vertical SiNWAs due to multiple scattering paths inside the nanowire arrays. On the other hand, inclined nanowires showed a fascinating behavior at the longer wavelength regime, where light gets the longer path to reflect back-forth and ease to reflect back outward at normal incidence. Moreover, for [100] SiNWAs, transverse electric field component demonstrates the strong polarization insensitive properties at the expense of transverse magnetic field component with a minimum reflectance of <2% up to 1200 nm. The [100] SiNWAs demonstrates extraordinary omnidirectional properties at θB ≥ 58°. Theoretical validation of COMSOL with an effective medium approach reveal the effective dipole coupling and the presence of strong absorption modes for vertical SiNWs at a typical wavelength regime. The highly bound states of the particle tunneling through classical forbidden region shows a strong dependence on the gradient in the refractive index (mi) from 1 to 3.4. The high order scattering effect is observed at ∼520 cm−1 in a disordered optical medium. This novel finding of light localization properties for SiNWAs with different orientation gives a new route to support various photonic applications.

An intuitive approach to structuring the three electric field components of light

This paper presents intuitive interpretations of tightly focused beams of light by drawing analogies with two-dimensional electrostatics, magnetostatics and fluid dynamics. We use a Helmholtz decomposition of the transverse electric field components in the transverse plane to introduce generalized radial and azimuthal polarization states. This reveals the interplay between transverse and longitudinal electric field components in a transparent fashion. Our approach yields a comprehensive understanding of tightly focused laser beams, which we illustrate through several insightful examples.

Performance analysis of a liquid-filled glass prism-coupled metal-clad planar waveguide sensor

The performance of a metal-clad planar waveguide-based sensor coupled with a liquid-filled prism is studied and is compared with a similar waveguide sensor coupled with a solid prism. The characteristic equations of these waveguides are obtained by matching field components at various boundaries, and the reflectivity of these waveguides is obtained using transfer matrix method. The obtained dispersion characteristic shows that the transverse electric field components are loosely bound in liquid-filled prism-coupled waveguide-based sensor. Unlike to solid prism-coupled waveguide sensor, the performance of liquid-filled prism-coupled waveguide sensor increases with increase of effective refractive index. Hence, the proposed liquid-filled prism-coupled waveguide-based sensor shows better performance at high effective refractive index.

Separating intracycle interferences in photoelectron momentum distributions by a polarization-gated pulse

We theoretically demonstrate the feasibility of separation of various of intracycle interferences in photoelectron momentum distributions (PMDs) with a polarization-gated (PG) pulse constructed by a left-circularly polarized and a time-delayed right-circularly polarized few-cycle laser pulse. By numerically solving the time-dependent Schrodinger equation, our simulations show that the intercycle interference pattern is suppressed and a clear interference pattern with rightward curved stripes emerges in PMDs with appropriate laser parameters. This interference pattern can be well reproduced by a quantum-trajectory Monte Carlo (QTMC) simulation and, moreover, with the help of QTMC analysis, up to three types of intracycle interferences can be identified. It is further revealed that the nonvanishing transverse electric-field component in the PG pulse plays an important role in separating various of intracycle interferences in PMDs by properly distributing the interference stripes of electron wave packets, emitted within different time windows, into different momentum regions and suppressing the forward-rescattering photoelectron holography.

Electromagnetic Waves in Multilayered Generalized Anisotropic Media

This paper presents the formulations for calculating the electromagnetic (EM) fields in multilayered generalized anisotropic media. Maxwell’s equations are written into a first-order differential (in $z$ ) equation concerning the transverse electric and magnetic field components in the spectral domain. The equation can be solved to obtain the EM fields in a homogeneous anisotropic medium. For fields in layered anisotropic media, the local transmission and reflection matrices, the global reflection matrices, and the recursion relations of the wave amplitudes at interfaces are derived and used to express the EM fields in arbitrary layers. The electric and magnetic dipole sources can locate in arbitrary layers, and the medium can have both full-tensor magnetic and dielectric anisotropy. The singular behavior of the solution in the close vicinity of the dipole source is subtracted to make the integrands decay rapidly as functions of $k_{x}$ and $k_{y}$ . The contributions of the subtracted part are calculated analytically. A three-layer anisotropic medium is modeled to show the convergence of the integrals with the singularity subtraction. To validate the algorithm for multilayered generalized anisotropic media, a five-layer medium is modeled and compared with finite element method results. The algorithm is also applied in geophysical EM well logging by modeling the triaxial induction logging tool. The responses in vertical and deviated wells are computed and compared with finite element results. The good agreement between the two results further validates the algorithm and demonstrates its capability to model induction logging tools in multilayered generalized anisotropic media.

Calculations of second harmonic generation with radially polarized excitations by elliptical mirror focusing.

Second harmonic generation (SHG) polarization intensity distribution illuminated with radially polarized beams by lens focusing appears two peaks, when the nonlinear optical coefficients dominate that is relevant to the transverse electric field components. Such two peaks pattern may result in ghosting and the decrement of imaging resolution. In this paper, an elliptical mirror based system is proposed in the case of radially polarized beams illumination for SHG. The calculated predictions and numerical simulations demonstrate that for radially polarized beams, the proportion of transverse field components at the focal plane under the condition of elliptical mirror focusing is 2.6 times smaller than that with lens focusing when its numerical aperture (NA) is 1. Furthermore, the full width at half maximum (FWHM) of the total field intensity profile is approximately 81% of that in a lens focusing system. Due to the enhancement of longitudinal components of incident field, the distribution of SHG polarization presents a single-peak pattern, in which two peaks can be observed with lens focusing. The SHG polarizations in collagen fiber, KTiOPO4 , and LiNbO3 have been numerical simulated and discussed in detail to verify the validity of the proposed method. LAY DESCRIPTION: A novel focusing mode for second harmonic generation (SHG) microscopy is described in this paper. In the case of radially polarized excitations, the SHG polarization distributions of some specimens appear two peaks pattern with traditional lens focusing. Such two peaks pattern may result in ghosting and the decrement of imaging resolution. By introducing elliptical mirror, the modulation of electric field at the focal plane can be realized. Thus, the distribution of SHG polarization is converted into a single-peak pattern which eliminates the ghosting and improves the spatial resolution on SHG images. This proposed method can be used for SHG in various materials and the full width at half maximum (FWHM) of SHG polarization will compress in different degrees. Besides, there is a significant improvement on signal-to-noise ratio in SHG imaging when an annular aperture illumination is applied. The focusing mode with elliptical mirror can also be utilized in other nonlinear optics areas such as polarized third harmonic generation (THG) measurements and two-photon fluorescence (TPF) microscopy.

Resonant Hall effect under generation of a self-sustaining mode of spin current in nonmagnetic bipolar conductors with identical characters between holes and electrons

We have proposed an enhancement mechanism of the Hall effect, the signal of which is amplified due to the generation of a sustaining mode of spin current. Our analytic derivations of the Hall resistivity revealed the conditions indispensable for the observation of the effect: (i) the presence of the transverse component of an effective electric field due to spin splitting in chemical potential in addition to the longitudinal component; (ii) the simultaneous presence of holes and electrons each having approximately the same characteristics; (iii) spin-polarized current injection from magnetized electrodes; (iv) the boundary condition for the transverse current (Jc,y = 0). The model proposed in this study was experimentally verified by using van der Pauw-type Hall devices consisting of the nonmagnetic bipolar conductor YHx (x ≃ 2) and TbFeCo electrodes. Replacing Au electrodes with TbFeCo electrodes alters the Hall resistivity from the ordinary Hall effect to the anomalous Hall-like effect with an enhancement factor of approximately 50 at 4 T. We interpreted the enhancement phenomenon in terms of the present model.

Study of the transverse and longitudinal electric field components of surface plasmon polaritons on flat metal film by polarization-resolved Fourier-space microscopy

We have employed a polarization-resolved Fourier-space surface plasmon resonance microscope to determine the electric field component ratio of surface plasmon polaritons (SPPs) propagating on a flat gold film. By using a metallic nanoparticle as a probe to capture the radiation damping of the SPP scattered waves, we find the angular far-field distribution is related to the transverse and longitudinal fields of SPPs. The experiment is supported by analytical and numerical calculations. Our results present a simple but useful approach to probe the behaviors of SPPs such as the transverse spin density as well as the energy density.