Field Polarization Vector Research Articles

Observation of accurately designed bound states in the continuum in momentum space

Bound states in the continuum (BICs) in artificial photonic structures have received considerable attention since they offer unique methods for the extreme field localization and enhancement of light-matter interactions. Usually, the symmetry-protected BICs are located at high symmetric points, while the positions of accidental BICs achieved by tuning the parameters will appear at some points in momentum space. Up to now, to accurately design the position of the accidental BIC in momentum space is still a challenge. Here, we theoretically and experimentally demonstrate an accurately designed accidental BIC in a two-coupled-oscillator system consisting of bilayer gratings, where the optical response of each grating can be described by a single resonator model. By changing the interlayer distance between the gratings to tune the propagation phase shift related to wave vectors, the position of the accidental BIC can be arbitrarily controlled in momentum space. Moreover, we present a general method and rigorous numerical analyses for extracting the polarization vector fields to observe the topological properties of BICs from the polarization-resolved transmission spectra. Finally, an application of the highly efficient second harmonic generation assisted by quasi-BIC is demonstrated. Our work provides a straightforward strategy for manipulating BICs and studying their topological properties in momentum space.

Image Encryption Through Dual-Pass Modulated Azimuthally Polarized Vector Field

Image Encryption Through Dual-Pass Modulated Azimuthally Polarized Vector Field

Spatial self-phase modulation excited by fractional-order linearly polarized vector fields.

Compared to the integer-order vector field, the fractional-order vector field has an additional degree of control freedom, which will bring rich photophysical properties and what we believe to be novel nonlinear optical phenomena. In this work, we theoretically and experimentally investigate the focusing, propagation, and spatial self-phase modulation (SSPM) of fractional-order linearly polarized vector fields (FLPVFs). It is shown that the weak focusing field of FLPVF exhibits an asymmetric intensity distribution. Intriguingly, its state of polarization (SoP) has a hybrid polarization distribution. When this focused FLPVF propagates to the far field in free space, its SoP degenerates into a localized linearly polarization distribution. However, after the focused FLPVF passes through an isotropic nonlinear Kerr medium, its SoP exhibits a hybrid polarization distribution. Additionally, unlike the self-diffraction intensity pattern of integer-order linearly polarized vector field (ILPVF) with a concentric multi-ring structure, the SSPM pattern of FLPVF is a symmetry broken self-diffraction intensity pattern. The presented work provides a nonlinear optics approach for manipulating both the SoP and intensity distributions of the light field.

A generalizable TCAD framework for silicon FinFET spin qubit devices with electrical control

We present a TCAD-based simulation framework established for quantum dot spin qubits in a silicon FinFET platform with all-electrical control of the spin state. The framework works down to 1K and consists of a two-step simulation chain, from definition of the quantum dot confinement potential with DC bias voltages, to calculation of microwave response electric field at qubit locations using small-signal AC analysis. An average field polarization vector at each quantum dot is extracted via a post-processing step. We demonstrate functionality of this approach by simulation of a recently reported two-qubit device in the form of a 5-gate silicon FinFET. The impact of the number of holes in each quantum dot on the MW response E-field polarization direction is further investigated for this device. The framework is easily generalizable to study future multi-qubit large-scale systems.

Dynamic polarization rotation and vector field steering based on phase change metasurface

Dynamic polarization rotation and vector field steering based on phase change metasurface

Temporal and Spatial Characteristics of the Global Skylight Polarization Vector Field

There are two widely recognized global fields in nature: the gravity field and the geomagnetic field. Universal gravitation and Earth rotation are important sources of the Earth’s gravity and geomagnetic fields, which are well known to us. After years of long-term observation, global research, and analysis, it was discovered that we have neglected a direct incident energy of the universe on the Earth. Solar radiation, leading to energy exchange from the atmosphere 100 km above the land surface, is the energy source of the Earth. Polarization is one of the four basic physical properties of solar radiation. After the solar radiation reaches the surface of these media, it reflects, scatters or refracts, and exhibits different degrees of polarization. The polarized solar light forms the Earth–sky polarization vector field. The polarized light dispersion is expected to become a new method for global analysis of the human environment. Polarization detection is the best way to accurately explore the atmospheric effects. Local polarized skylight distribution was found in different sites in the world; however, the global distribution of the polarized sunlight radiation has never been explored. In this paper, we investigate the Global Skylight Polarization Field. This study aimed at providing new insight into the laws of polarization over our Earth. We use a Rayleigh scattering model to obtain the simulation results of the sky polarization field. Rayleigh scattering occurs when the particle size is much smaller than the wavelength of the incident electromagnetic wave. We also use a polarized fisheye camera to collect the sky polarization image and calculate the distribution pattern of the DOLP (degree of linear polarization) and AOLP (azimuth of linear polarization) of the skylight. The stability and gradual change in the degree of polarization in the zenith direction are verified, and the distribution law and daily change law of the degree of polarization in the sky are obtained. With the increase in the solar altitude angle, the degree of polarization will decrease. We also observed the skylight polarization in different weather conditions. Our results demonstrate the physical basis, characteristics, and usability of the polarization field. They show an inevitable trend from optical remote sensing to polarization remote sensing.

Laser-assisted charge transfer in positronium collisions with protons and antiprotons

We study the process of laser-assisted charge transfer in collisions of positronium atoms with protons (antiprotons) with formation of Rydberg hydrogen (antihydrogen) atoms by the use of classical trajectories Monte Carlo simulations of Ps-$p$ dynamics in a linearly polarized infrared field. We do not observe a drastic enhancement of the cross sections similar to that predicted before in laser-assisted electron bremsstrahlung and electron recombination since in the present charge-transfer process the Coulomb focusing effect is absent. Still we see a substantial enhancement up to a factor of 3 in the energy range between ${10}^{\ensuremath{-}4}$ and 0.1 eV for the field of intensity between 10 $\mathrm{MW}/{\mathrm{cm}}^{2}$ and 10 $\mathrm{GW}/{\mathrm{cm}}^{2}$. The effect depends weakly on the orientation of the incident Ps velocity relative to the field polarization vector. Rydberg states of the produced hydrogen atoms whose orbits are close to circular can survive against ionization by laser field and decay spontaneously to lower states. This is favorable for spectroscopic studies of antihydrogen atoms.

Phase field model for cell spreading dynamics.

We suggest a 3D phase field model to describe 3D cell spreading on a flat substrate. The model is a simplified version of a minimal model that was developed in Winkler (Commun Phys 2:82, 2019). Our model couples the order parameter u with 3D polarization (orientation) vector field [Formula: see text] of the actin network. We derive a closed integro-differential equation governing the 3D cell spreading dynamics on a flat substrate, which includes the normal velocity of the membrane, curvature, volume relaxation rate, a function determined by the molecular effects of the subcell level, and the adhesion effect. This equation is easily solved numerically. The results are in agreement with the early fast phase observed experimentally in Dobereiner (Phys Rev Lett 93:108105, 2004). Also we find agreement with the universal power law (Cuvelier in Curr Biol 17:694-699, 2007) which suggest that cell adhesion or contact area versus time behave as [Formula: see text] in the early stage of cell spreading dynamics, and slow down at the next stages.

Polarization vector formalism of plasma weak turbulence

This paper formulates the plasma weak turbulent theory based on the unit electric field polarization vector. This concept is not intrinsically new, and partial formulations of weak turbulence processes based on the polarization vector approach are found in the literature. However, the present paper applies such a method uniformly to all the relevant processes for the first time, thus unifying the existing formalisms. The present result potentially provides many advantages including the fact that it facilitates the complex manipulations of various tensor coupling coefficients that dictate the wave–wave and nonlinear wave–particle interactions. To demonstrate its validity, the limit of unmagnetized plasmas is considered, and it is shown that the known results are recovered. The present formalism can be extended to more complex situations including magnetized plasmas, which is a subject of future work.

Electromagnetic curves and Rytov curves based on the hyperbolic split quaternion algebra

This paper aims to investigate the hyperbolically the motion of the polarization plane traveling along the linearly polarized light wave in the optical fiber via the hyperbolic split quaternion algebra. The motion of the electric field (polarization vector) about an axis on the general hyperboloid is described by the Lorentzian scalar product space Ra1,a2,a32,1. The hyperbolic geometric (Berry) phase models are generated through the pseudo-spheres of Ra1,a2,a32,1. Then, the parametric representations of the Rytov curves are obtained via the hyperbolic split quaternion product and one-parameter homothetic motion. Then, the hyperbolically motion of the electric field is expressed by the Fermi–Walker parallel transportation law. Moreover, the electromagnetic curves (EM-curves) associated with the electric field E are determined via the hyperbolic geometric phase models in the optical fiber. Furthermore, some motivating examples are presented by using the MAPLE program.

Manipulating light radiation from a topological perspective

Manipulating radiation is important for a variety of optoelectronic applications, such as on-chip lasers, energy-efficient grating couplers, and antennas for light detection and ranging. Although designing and optimizing those optoelectronic devices are usually believed to be an engineering-oriented task, recent research reveals that the principles underlying radiation manipulation are closely connected to the concept of topology—the study of properties that are invariant under continuous deformations. In this review, we summarize a series of advances of the physics, phenomena, and applications related to radiation manipulation, in which topological concepts were adopted. Radiation could carry energy escaping from the system, breaking the energy conservation. The non-Hermiticity of such systems brings quite different physical consequences when comparing with the Hermitian counterparts and, hence, also results in the emergence of many interesting and extraordinary phenomena. In particular, it is found that the perfect trapping of light can still be realized in such non-Hermitian systems because of the photonic realization of bound states in the continuum. The fundamental nature of bound states in the continuum has been identified to be topological: they are essentially topological defects of the polarization vector field in momentum space, depicted by a kind of topological invariant named topological charges. Therefore, manipulation of radiation channels can be realized by controlling the topological charge evolution in momentum space. It is also demonstrated that the photonic states accompanied with different topological charges generate vortex beams with unique far-field radiation patterns, and ultra-fast switching of such vortex beams is demonstrated according to this principle. The progresses of topological photonics upon light radiation show that the topology is not just mathematical convenience for depicting photonic systems, but has brought realistic consequences in manipulating light and will boost the applications of photonics and optoelectronics in many aspects.

Local atomic geometry and Ti 1s near-edge spectra in PbTiO3 and SrTiO3.

We study Ti 1s near-edge spectroscopy in PbTiO3 at various temperatures above and below its tetragonal-to-cubic phase transition, and in SrTiO3 at room temperature. Ab initio molecular dynamics (AIMD) runs on 80-atom supercells are used to determine the average internal coordinates and their fluctuations. We determine that one vector local order parameter is the dominant contributor to changes in spectral features: the displacement of the Ti ion with respect to its axial O neighbors in each Cartesian direction, as these displacements enhance the cross section for transitions to Eg-derived core-hole exciton levels. Using periodic five-atom structures whose relative Ti-O displacements match the root-mean-square values from the AIMD simulations, and core-hole Bethe-Salpeter equation (BSE) calculations, we quantitatively predict the respective Ti 1s near-edge spectra. Properly accounting for atomic fluctuations greatly improves the agreement between theoretical and experimental spectra. The evolution of relative strengths of spectral features vs temperature and electric field polarization vector are captured in considerable detail. This work shows that local structure can be characterized from first-principles sufficiently well to aid both the prediction and the interpretation of near-edge spectra.

Theoretical investigation on asymmetrical spinning and orbiting motions of particles in a tightly focused power-exponent azimuthal-variant vector field.

We generate a new kind of azimuthal-variant vector field with a distribution of states of polarization (SoPs) described by the square of the azimuthal angle. Owing to asymmetrical SoPs distribution of this localized linearly polarized vector field, the tightly focused field exhibits a double half-moon shaped pattern with the localized elliptical polarization in the cross section of field at the focal plane. Moreover, we study the three-dimensional distributions of spin and orbital linear and angular momenta in the focal region. We numerically investigate the gradient force, radiation force, spin torque, and orbital torque on a dielectric Rayleigh particle produced by the tightly focused vector field. It is found that asymmetrical spinning and orbiting motions of trapped Rayleigh particles can be realized by the use of a tight vector field with power-exponent azimuthal-variant SoPs.

An Extended Newmark-FDTD Method for Complex Dispersive Media

Based on polarizability in the form of a complex quadratic rational function, a novel finite-difference time-domain (FDTD) approach combined with the Newmark algorithm is presented for dealing with a complex dispersive medium. In this paper, the time-stepping equation of the polarization vector is derived by applying simultaneously the Newmark algorithm to the two sides of a second-order time-domain differential equation obtained from the relation between the polarization vector and electric field intensity in the frequency domain by the inverse Fourier transform. Then, its accuracy and stability are discussed from the two aspects of theoretical analysis and numerical computation. It is observed that this method possesses the advantages of high accuracy, high stability, and a wide application scope and can thus be applied to the treatment of many complex dispersion models, including the complex conjugate pole residue model, critical point model, modified Lorentz model, and complex quadratic rational function.

Electrostatic built-in fields in wurtzite III-N nanostructures: Impact of growth plane on second-order piezoelectricity

In this work we present a detailed analysis of the second-order piezoelectric effect in wurtzite III-N heterostructures, such as quantum wells and quantum dots, grown on different substrate orientations. Our analysis is based on a continuum model using a here derived analytic expression for the second-order piezoelectric polarization vector field as a function of the incline angle $\ensuremath{\theta}$ to the wurtzite $c$ axis. This expression allows for a straightforward implementation in existing quantum well and quantum dot codes. Our calculations on III-N quantum well systems reveal that especially for semipolar structures with high incline angle values (${55}^{\ensuremath{\circ}}\ensuremath{\le}\ensuremath{\theta}\ensuremath{\le}{80}^{\ensuremath{\circ}}$ and ${105}^{\ensuremath{\circ}}\phantom{\rule{0.16em}{0ex}}\ensuremath{\le}\phantom{\rule{0.16em}{0ex}}\ensuremath{\theta}\phantom{\rule{0.16em}{0ex}}\ensuremath{\le}\phantom{\rule{0.16em}{0ex}}{120}^{\ensuremath{\circ}}$), second-order piezoelectricity noticeably contributes to the overall electric built-in field. For instance, in an InGaN/GaN multiple quantum well system with 22% In, the electric field increases by approximately 20% due to second-order piezoelectricity. Overall, when including second-order piezoelectric effects in the calculation of electric fields in GaN/AlN and InGaN/GaN quantum well systems an improved agreement between our theory and experimental literature data is observed. When studying quantum dots, at least for the here considered model geometry and growth planes, we observe that for GaN/AlN structures second-order effects are of secondary importance. The situation is different for non-$c$-plane ${\mathrm{In}}_{0.2}{\mathrm{Ga}}_{0.8}\mathrm{N}$/GaN quantum dots. For example, inside a nonpolar ${\mathrm{In}}_{0.2}{\mathrm{Ga}}_{0.8}\mathrm{N}$/GaN dot the built-in potential arising from second-order piezoelectricity is comparable in magnitude to the built-in potential originating from spontaneous and first-order piezoelectric polarization, but opposite in sign. This feature leads to a change in the built-in potential profile both in and around the ${\mathrm{In}}_{0.2}{\mathrm{Ga}}_{0.8}\mathrm{N}$/GaN quantum dot structure, which in general is relevant for electronic and optical properties of these systems.

Unveiling stability of multiple filamentation caused by axial symmetry breaking of polarization

Femtosecond laser filamentation is generally initialized from unpredictable symmetry breaking caused by random noise, causing it to be barely controlled. However, it is always anticipated for stable and controllable filamentation. We present and demonstrate the idea that hybridly polarized vector fields with axial symmetry broken polarization, associated with a pair of orthogonally linearly polarized vortices carrying the opposite-handed orbital angular momenta, could achieve controllable and robust multiple filamentation. Here, our motivation is to unveil the underlying physics behind such controllable and robust multiple filamentation. The symmetry breaking should first be actively controllable and then be able to effectively inhibit random noise. Robust multiple filamentation is inseparable from the fact that the phases between the multiple filaments are always locked. In contrast, uncontrollable multiple filamentation is always accompanied with loss of phase, i.e., the multiple filaments become incoherent to each other. Our results may offer a suggestion for achieving controllable and robust multiple filamentation in other systems.

Arbitrarily tunable orbital angular momentum of photons.

Orbital angular momentum (OAM) of photons, as a new fundamental degree of freedom, has excited a great diversity of interest, because of a variety of emerging applications. Arbitrarily tunable OAM has gained much attention, but its creation remains still a tremendous challenge. We demonstrate the realization of well-controlled arbitrarily tunable OAM in both theory and experiment. We present the concept of general OAM, which extends the OAM carried by the scalar vortex field to the OAM carried by the azimuthally varying polarized vector field. The arbitrarily tunable OAM we presented has the same characteristics as the well-defined integer OAM: intrinsic OAM, uniform local OAM and intensity ring, and propagation stability. The arbitrarily tunable OAM has unique natures: it is allowed to be flexibly tailored and the radius of the focusing ring can have various choices for a desired OAM, which are of great significance to the benefit of surprising applications of the arbitrary OAM.

The Sensitivity of the Distance Dependent Plasmonic Coupling between Two Nanocubes to their Orientation: Edge-to-Edge versus Face-to-Face

Using DDA calculations, the electromagnetic field distribution and polarization vector plots were calculated as functions of the separation distance between a pair of 42-nm Ag nanocube dimers oriented in either an edge-to-edge or face-to-face configuration. We found that, as the separation distance of the nanocube dimer is decreased, the orientation of the dimer dramatically affects its near-field coupling behavior. The expected dipole–dipole exponential coupling behavior between the surfaces of the two nanocubes was found to fail at a separation distance of 6 nm for the face–to-face configuration and 14 nm for the edge-to-edge arrangement. The failure of the dipole–dipole coupling mechanism results from an increased contribution from the higher-order multipoles (e.g., quadrupole–dipole). Because this failure occurs at a larger separation distance for the edge-to-edge orientation, the relative ratio of the multipole to the dipole moment generated by the edge-to-edge dimer must be larger than the ratio for...

Hyperbolic-symmetry vector fields.

We present and construct a new kind of orthogonal coordinate system, hyperbolic coordinate system. We present and design a new kind of local linearly polarized vector fields, which is defined as the hyperbolic-symmetry vector fields because the points with the same polarization form a series of hyperbolae. We experimentally demonstrate the generation of such a kind of hyperbolic-symmetry vector optical fields. In particular, we also study the modified hyperbolic-symmetry vector optical fields with the twofold and fourfold symmetric states of polarization when introducing the mirror symmetry. The tight focusing behaviors of these vector fields are also investigated. In addition, we also fabricate micro-structures on the K9 glass surfaces by several tightly focused (modified) hyperbolic-symmetry vector fields patterns, which demonstrate that the simulated tightly focused fields are in good agreement with the fabricated micro-structures.

Manipulation of dielectric Rayleigh particles using highly focused elliptically polarized vector fields.

Generation of vectorial optical fields with arbitrary polarization distribution is of great interest in areas where exotic optical fields are desired. In this work, we experimentally demonstrate the versatile generation of linearly polarized vector fields, elliptically polarized vector fields, and circularly polarized vortex beams through introducing attenuators in a common-path interferometer. By means of Richards-Wolf vectorial diffraction method, the characteristics of the highly focused elliptically polarized vector fields are studied. The optical force and torque on a dielectric Rayleigh particle produced by these tightly focused vector fields are calculated and exploited for the stable trapping of dielectric Rayleigh particles. It is shown that the additional degree of freedom provided by the elliptically polarized vector field allows one to control the spatial structure of polarization, to engineer the focusing field, and to tailor the optical force and torque on a dielectric Rayleigh particle.