Showing papers on "Plane wave published in 2017"
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30 Oct 2017
TL;DR: In this paper, the authors present a theory based on power balance for aperture excitation of electrically large, lossy cavities, which yields expressions for shielding effectiveness, cavity Q, and cavity time constant.
Abstract: We present a theory based on power balance for aperture excitation of electrically large, lossy cavities. The theory yields expressions for shielding effectiveness, cavity Q, and cavity time constant. In shielding effectiveness calculations, the incident field can be either a single plane wave or a uniformly random field to model reverberation chamber or random field illumination. The Q theory includes wall loss, absorption by lossy objects within the cavity, aperture leakage, and power received by antennas within the cavity. Extensive measurements of shielding effectiveness, cavity Q, and cavity time constant were made on a rectangular cavity, and good agreement with theory was obtained for frequencies from 1 to 18 GHz. >
389 citations
TL;DR: A coherent perfect absorber is a system in which complete absorption of electromagnetic radiation is achieved by controlling the interference of multiple incident waves as discussed by the authors, which can be made much more efficient by exploiting wave interference.
Abstract: Absorption of electromagnetic energy by a material is a phenomenon that underlies many applied problems, including molecular sensing, photocurrent generation and photodetection. Commonly, the incident energy is delivered to the system through a single channel, for example by a plane wave incident on one side of an absorber. However, absorption can be made much more efficient by exploiting wave interference. A coherent perfect absorber is a system in which complete absorption of electromagnetic radiation is achieved by controlling the interference of multiple incident waves. Here, we review recent advances in the design and applications of such devices. We present the theoretical principles underlying the phenomenon of coherent perfect absorption and give an overview of the photonic structures in which it can be realized, including planar and guided-mode structures, graphene-based systems, parity- and time-symmetric structures, 3D structures and quantum-mechanical systems. We then discuss possible applications of coherent perfect absorption in nanophotonics and, finally, we survey the perspectives for the future of this field.
240 citations
TL;DR: A coherent perfect absorber is a system in which the complete absorption of electromagnetic radiation is achieved by controlling the interference of multiple incident waves as mentioned in this paper, which is a phenomenon that underlies many applications including molecular sensing, photocurrent generation and photodetection.
Abstract: The absorption of electromagnetic energy by a material is a phenomenon that underlies many applications, including molecular sensing, photocurrent generation and photodetection. Typically, the incident energy is delivered to the system through a single channel, for example, by a plane wave incident on one side of an absorber. However, absorption can be made much more efficient by exploiting wave interference. A coherent perfect absorber is a system in which the complete absorption of electromagnetic radiation is achieved by controlling the interference of multiple incident waves. Here, we review recent advances in the design and applications of such devices. We present the theoretical principles underlying the phenomenon of coherent perfect absorption and give an overview of the photonic structures in which it can be realized, including planar and guided-mode structures, graphene-based systems, parity-symmetric and time-symmetric structures, 3D structures and quantum-mechanical systems. We then discuss possible applications of coherent perfect absorption in nanophotonics, and, finally, we survey the perspectives for the future of this field.
204 citations
TL;DR: This work develops a powerful strategy to realize chiral microstructures in isotropic material by coaxial interference of a vortex beam and a plane wave, which produces three-dimensional (3D) spiral optical fields.
Abstract: Optical vortices, a type of structured beam with helical phase wavefronts and ‘doughnut’-shaped intensity distributions, have been used to fabricate chiral structures in metals and spiral patterns in anisotropic polarization-dependent azobenzene polymers. However, in isotropic polymers, the fabricated microstructures are typically confined to non-chiral cylindrical geometry due to the two-dimensional ‘doughnut’-shaped intensity profile of the optical vortices. Here we develop a powerful strategy to realize chiral microstructures in isotropic material by coaxial interference of a vortex beam and a plane wave, which produces three-dimensional (3D) spiral optical fields. These coaxial interference beams are generated by designing contrivable holograms consisting of an azimuthal phase and an equiphase loaded on a liquid-crystal spatial light modulator. In isotropic polymers, 3D chiral microstructures are achieved under illumination using coaxial interference femtosecond laser beams with their chirality controlled by the topological charge. Our further investigation reveals that the spiral lobes and chirality are caused by interfering patterns and helical phase wavefronts, respectively. This technique is simple, stable and easy to perform, and it offers broad applications in optical tweezers, optical communications and fast metamaterial fabrication. Helical microstructures can be directly polymerized into standard photoresists using beams derived from interfering holograms. Recent studies have shown that optical vortices can pattern polymer surfaces with the same left- or right-handed chirality of the spinning light beam, but only if the material’s structure has a built-in asymmetry. Dong Wu and co-workers from the University of Science and Technology of China report that optical vortices generated by liquid-crystal devices called spatial light modulators (SLMs) are stable enough to engrave chiral microstructures into more-common isotropic polymers. Directing femtosecond laser pulses onto an SLM produced holograms and plane waves that interfered and co-propagated into helices without the phase sensitivity of typical split-beam setups. This approach enabled controllable fabrication of spiral patterns with different lobes and orientations over large areas with a 100-nanometer-scale precision.
172 citations
TL;DR: In this article, the authors proposed an ultrathin complementary metasurface that converts a left-handed (right-handed) circularly polarized plane wave without orbital angular momentum (OAM), which is associated with the azimuthal phase of the complex electric field.
Abstract: Electromagnetic (EM) waves with helical wave front carry orbital angular momentum (OAM), which is associated with the azimuthal phase of the complex electric field. OAM is a new degree of freedom in EM waves and is promising for channel multiplexing in the communication system. Although the OAM-carrying EM wave attracts more and more attention, the method of OAM generation at microwave frequencies still faces challenges, such as efficiency and simulation time. In this communication, by using the circuit theory and equivalence principle, we build two simplified models, one for a single scatter and one for the whole metasurface to predict their EM responses. Both of the models significantly simplify the design procedure and reduce the simulation time. In this communication, we propose an ultrathin complementary metasurface that converts a left-handed (right-handed) circularly polarized plane wave without OAM to a right-handed (left-handed) circularly polarized wave with OAM of arbitrary orders, and a high transmission efficiency can be achieved.
123 citations
Abstract: The “gravitational memory effect” due to an exact plane wave provides us with an elementary description of the diffeomorphisms associated with the analogue of “soft gravitons for this nonasymptotically flat system. We explain how the presence of the latter may be detected by observing the motion of freely falling particles or other forms of gravitational wave detection. Numerical calculations confirm the relevance of the first, second and third time integrals of the Riemann tensor pointed out earlier. Solutions for various profiles are constructed. It is also shown how to extend our treatment to Einstein-Maxwell plane waves and a midisuperspace quantization is given.
119 citations
TL;DR: In this article, an account of the velocities of soft gravitons in the presence of the exact plane wave solution of Einstein's vacuum equations is given, and a non-vanishing asymptotic relative velocity is used to detect gravitational waves through the velocity memory effect, considered by Braginsky, Thorne, Grishchuk and Polnarev.
119 citations
TL;DR: In this article, the first and higher harmonic components of the resonant fluid response in the gap between two identical fixed rectangular boxes are experimentally investigated in a wave basin and it is shown that for an incident group with appropriate frequency content, the linear gap response may be substantially smaller than the second-harmonic component, which is strongly driven via quadratic coupling of the linear terms from the incident wave and occurs in gap resonant modes.
Abstract: The first- and higher-harmonic components of the resonant fluid response in the gap between two identical fixed rectangular boxes are experimentally investigated in a wave basin. Gap response is excited by transient wave groups (being based on scaled versions of the autocorrelation function of sea state spectra, representing NewWaves, the average shape of large waves in a sea state). Several different wave groups with different maximum surface elevations, spectral peak frequencies and bandwidths are used, while the bilge shape of the boxes and approach angle of the waves are also varied. Unlike a simple regular wave, it is complicated to separate the harmonic components for a transient wave group due to non-linear wave-wave and wave-structure interactions. A four-phase combination methodology is used to separate the first four harmonic components, and this also allows higher-harmonic components to be isolated with simple digital frequency filtering. Harmonic components up to 14th order in the incident wave amplitude have been extracted. It is shown that for an incident group with appropriate frequency content, the linear gap response may be substantially smaller than the second-harmonic component, which is strongly driven via quadratic coupling of the linear terms from the incident wave and occurs in the gap resonant modes. Double frequency excitation may have important practical implications for offshore operations. Fourth and zeroth (long wave) harmonics in the gap are further driven via quadratic coupling of the second-harmonic itself. Linear damping coefficients for the first few modes of the gap resonant response are derived from measured time series using a numerical fit and shown to be higher than those from linear diffraction calculations.
101 citations
TL;DR: In this paper, a traveling-wave circular slot antenna that can generate plane spiral OAM waves is developed and experimentally demonstrated, and the antenna is excited by a 90 $^\circ$ hybrid coupler.
Abstract: Plane spiral orbital angular momentum (OAM) wave is a new form of OAM-carrying electromagnetic wave that propagates along the transverse direction. A traveling-wave circular slot antenna that can generate plane spiral OAM waves is developed and experimentally demonstrated in this letter. The antenna is excited by a 90 $^\circ$ hybrid coupler. In order to ensure that the OAM waves are propagating along the transverse plane, a ring horn is added outside the antenna. A prototype with OAM states l = $\pm$ 3 for 10-GHz operation is fabricated and measured. The near-field phase distributions clearly indicate the azimuth phase shifting, and the radiation patterns show the characteristic of transverse propagation, respectively. The proposed antenna provides a novel approach to implement an OAM wireless communication link that has no phase singularity or divergence problem.
99 citations
TL;DR: In this article, the wave propagation of size-dependent functionally graded (FG) nanobeams resting on elastic foundation subjected to axial magnetic field based on the nonlocal strain gradient theory and Euler-Bernoulli beam model was investigated by using an analytical approach.
Abstract: This paper investigates wave propagation of size-dependent functionally graded (FG) nanobeams resting on elastic foundation subjected to axial magnetic field based on the nonlocal strain gradient theory and Euler–Bernoulli beam model by using an analytical approach. The nonlocal beam model has a length scale parameter and captures the size influences. Material properties are spatially graded according to sigmoid distribution. A derivation of the governing equations for the wave propagation analysis of nanoscale S-FGM beams is conducted. Then, the dispersion relations between wave frequency and phase velocity with the wave number is investigated. It is found that wave propagation characteristics of nonlocal S-FGM beams are influenced by various parameters including length scale parameter, material graduation, elastic foundation parameters and magnetic field intensity.
90 citations
TL;DR: A mixed density fitting scheme is introduced that uses both a Gaussian and a plane-wave fitting basis to accurately evaluate electron repulsion integrals in crystalline systems to enable efficient all-electron Gaussian based periodic density functional and Hartree-Fock calculations.
Abstract: We introduce a mixed density fitting scheme that uses both a Gaussian and a plane-wave fitting basis to accurately evaluate electron repulsion integrals in crystalline systems. We use this scheme to enable efficient all-electron Gaussian based periodic density functional and Hartree-Fock calculations.
TL;DR: In this article, the authors identified the 5-parameter isometry group of plane gravitational waves in $4$ dimensions as Levy-Leblond's Carroll group in $2+1$ dimensions with no rotations.
Abstract: The well-known 5-parameter isometry group of plane gravitational waves in $4$ dimensions is identified as Levy-Leblond's Carroll group in $2+1$ dimensions with no rotations. Our clue is that plane waves are Bargmann spaces into which Carroll manifolds can be embedded. We also comment on the scattering of light by a gravitational wave and calculate its electric permittivity considered as an impedance-matched metamaterial.
TL;DR: In this article, a general bi-Helmholtz nonlocal strain-gradient elasticity model is developed for wave dispersion analysis of porous double-nanobeam systems in thermal environments.
TL;DR: In this paper, the propagation of time harmonic plane waves is investigated in an infinite nonlocal elastic solid material with voids, and the governing relations and equations are derived for nonlinear elastic solid with void.
Abstract: In this paper, the governing relations and equations are derived for nonlocal elastic solid with voids. The propagation of time harmonic plane waves is investigated in an infinite nonlocal elastic solid material with voids. It has been found that three basic waves consisting of two sets of coupled longitudinal waves and one independent transverse wave may travel with distinct speeds. The sets of coupled waves are found to be dispersive, attenuating and influenced by the presence of voids and nonlocality parameters in the medium. The transverse wave is dispersive but non-attenuating, influenced by the nonlocality and independent of void parameters. Furthermore, the transverse wave is found to face critical frequency, while the coupled waves may face critical frequencies conditionally. Beyond each critical frequency, the respective wave is no more a propagating wave. Reflection phenomenon of an incident coupled longitudinal waves from stress-free boundary surface of a nonlocal elastic solid half-space with voids has also been studied. Using appropriate boundary conditions, the formulae for various reflection coefficients and their respective energy ratios are presented. For a particular model, the effects of non-locality and dissipation parameter (
$\tau $
) have been depicted on phase speeds and attenuation coefficients of propagating waves. The effect of nonlocality on reflection coefficients has also been observed and shown graphically.
TL;DR: In this paper, the same set of molecules were inspected using the projector augmented wave method and the Vienna ab initio simulation package (VASP) for the ionization potential, and the basis set extrapolated plane wave results agree very well with the Gaussian basis sets, often reaching better than 50 meV agreement.
Abstract: In a recent work, van Setten and co-workers have presented a carefully converged G0W0 study of 100 closed shell molecules [J. Chem. Theory Comput. 2015, 11, 5665−5687]. For two different codes they found excellent agreement to within a few 10 meV if identical Gaussian basis sets were used. We inspect the same set of molecules using the projector augmented wave method and the Vienna ab initio simulation package (VASP). For the ionization potential, the basis set extrapolated plane wave results agree very well with the Gaussian basis sets, often reaching better than 50 meV agreement. In order to achieve this agreement, we correct for finite basis set errors as well as errors introduced by periodically repeated images. For positive electron affinities differences between Gaussian basis sets and VASP are slightly larger. We attribute this to larger basis set extrapolation errors for the Gaussian basis sets. For quasi particle (QP) resonances above the vacuum level, differences between VASP and Gaussian basis ...
TL;DR: named KGEC ([K]ubo [G]reenwood [E]lectronic [C]onductivity], the code calculates the full complex conductivity tensor (not just the average trace), and provides both Gaussian and Lorentzian representations of the Dirac delta function (though the LorentZian is preferable on basic grounds).
TL;DR: In this article, the axial and transverse radiation force cross-sections of optical tractor Bessel polarized beams are theoretically investigated for a dielectric sphere with particular emphasis on the beam topological charge (or order), half-cone angle and polarization.
Abstract: Axial and transverse radiation force cross-sections of optical tractor Bessel polarized beams are theoretically investigated for a dielectric sphere with particular emphasis on the beam topological charge (or order), half-cone angle and polarization. The angular spectrum decomposition method (ASDM) is used to derive the non-paraxial electromagnetic (EM) field components of the Bessel beams. The multipole expansion method using vector spherical harmonics is utilized and appropriate beam-shape coefficients are derived in order to compute the radiation force cross-sections. The analysis has no limitation to a particular range of frequencies such that the Rayleigh, Mie or geometrical optics regimes can all be considered effectively using the present rigorous formalism. The focus of this investigation is to identify some of the tractor beam conditions so as to achieve retrograde motion of a dielectric sphere located arbitrarily in space. Numerical computations for the axial and transverse radiation force cross-sections are presented for linear, right-circular, radial, azimuthal and mixed polarizations of the individual plane waves forming the Bessel beams of zeroth- and first-order (with positive or negative helicity), respectively. As the sphere shifts off the beam׳s axis, the axial pulling (tractor) force is weakened. Moreover, the transverse radiation force cross-section field changes with the sphere׳s size factor ka (where k is the wavenumber and a is the sphere radius). Both stable and unstable equilibrium regions around the beam׳s axis are found, depending on the choice of ka and the half-cone angle α0. These results are particularly important in the development of emergent technologies for the photophoretic assembly of optically-engineered (meta)materials with designed properties using optical tractor (vortex) beams, particle manipulation, levitation and positioning, and other applications.
TL;DR: In this article, a distributed circuit modeling based on analytical study of the tunable enhanced lateral displacement of electromagnetic waves in total reflection of light beams from a graphene containing structure is presented, which can be used in designing graphene plasmonic based integrated optical devices such as optical switches.
TL;DR: In this article, a simple and efficient approach for multipole expansion of a circularly symmetric Bessel beam is derived, and the convergence and correctness of the beam shape coefficients are verified numerically in detail for both on-axis and off-axis cases.
TL;DR: In this article, an extended trial equation method was employed to retrieve nematicons in liquid crystals from its governing equation and several other forms of solution naturally emerged from the integration algorithm.
Abstract: This paper employs extended trial equation method to retrieve nematicons in liquid crystals from its governing equation. In addition, several other forms of solution naturally emerged from the integration algorithm. These are shock waves, singular solitons, snoidal waves, periodic singular waves, plane waves and others. These variety of solutions are being reported for the first time in the context of liquid crystals.
TL;DR: In this article, the scattering and absorption of the H and E-polarized plane waves by an infinite flat graphene strip grating placed in a dielectric slab, in the THz range, were considered.
Abstract: We considered the scattering and absorption of the H and E-polarized plane waves by an infinite flat graphene strip grating placed in a dielectric slab, in the THz range. Accurate numerical treatment was based on the singular integral equations and their projection to specially tailored orthogonal polynomials. The resulting numerical algorithm possessed guaranteed convergence and provided controlled accuracy. Reflectance, transmittance, and absorbance were studied, and the resonances on the surface-plasmon modes, the grating modes, and the slab modes were identified. The grating or lattice modes are caused by the periodicity. Their complex frequencies are extremely close to Rayleigh anomalies and therefore the Q-factors are extraordinarily high, which makes them promising in various applications.
TL;DR: The mathematics of multiple component shear wave fields are explored and the basic properties are derived, from which efficient estimators can be obtained, and the expected value of displacement patterns in shear reverberant fields are derived.
Abstract: The determination of shear wave speed is an important subject in the field of elastography, since elevated shear wave speeds can be directly linked to increased stiffness of tissues. MRI and ultrasound scanners are frequently used to detect shear waves and a variety of estimators are applied to calculate the underlying shear wave speed. The estimators can be relatively simple if plane wave behavior is assumed with a known direction of propagation. However, multiple reflections from organ boundaries and internal inhomogeneities and mode conversions can create a complicated field in time and space. Thus, we explore the mathematics of multiple component shear wave fields and derive the basic properties, from which efficient estimators can be obtained. We approach this problem from the historic perspective of reverberant fields, a conceptual framework used in architectural acoustics and related fields. The framework can be recast for the alternative case of shear waves in a bounded elastic media, and the expected value of displacement patterns in shear reverberant fields are derived, along with some practical estimators of shear wave speed. These are applied to finite element models and phantoms to illustrate the characteristics of reverberant fields and provide preliminary confirmation of the overall framework.
TL;DR: In this article, a closed-form semi-analytical solution for the vibrations due to a moving point load in a tunnel embedded in a half-space is given, where the tunnel is modelled as an elastic hollow cylinder and the ground surrounding the tunnel as a linear viscoelastic material.
TL;DR: In this article, the authors consider the question of how to extend this relationship to curved scattering backgrounds, focusing on certain'sandwich' plane waves and calculate the 3-point amplitudes on these backgrounds and find that a notion of double copy remains in the presence of background curvature.
Abstract: Perturbatively around flat space, the scattering amplitudes of gravity are related to those of Yang-Mills by colour-kinematic duality, under which gravitational amplitudes are obtained as the 'double copy' of the corresponding gauge theory amplitudes. We consider the question of how to extend this relationship to curved scattering backgrounds, focusing on certain 'sandwich' plane waves. We calculate the 3-point amplitudes on these backgrounds and find that a notion of double copy remains in the presence of background curvature: graviton amplitudes on a gravitational plane wave are the double copy of gluon amplitudes on a gauge field plane wave. This is non-trivial in that it requires a non-local replacement rule for the background fields and the momenta and polarization vectors of the fields scattering on the backgrounds. It must also account for new 'tail' terms arising from scattering off the background. These encode a memory effect in the scattering amplitudes, which naturally double copies as well.
TL;DR: In this paper, the authors present a procedure for the systematic estimation of the dispersion properties of linear discrete systems with periodic time-varying coefficients, which relies on the analysis of a single unit cell, making use of Bloch theorem along with the application of a harmonic balance methodology over an imposed solution ansatz.
TL;DR: Using the calculated transmission, the “tau”, the optical thickness, which describes the magnitude of the transmission is derived, and the NMM3D results are in close agreement with those of EP, DBA, and RTE.
Abstract: Transmission, scattering, and absorption by a layer of dielectric cylinders are studied in the context of microwave propagation through vegetation. The electromagnetic fields are calculated by numerical solutions of 3D Maxwell equations (NMM3D) using the method of Foldy-Lax multiple scattering equations combined with the method of the body of revolution (BOR). Using the calculated transmission, we derive, the “tau”, the optical thickness, which describes the magnitude of the transmission. Two cases are considered: the short-cylinder case and the extended-cylinder case. The case of short cylinders is that the lengths of cylinders are much smaller than the layer thickness, while the case of extended cylinders is that the lengths of the cylinders are the same as or comparable to the layer thickness. Numerical results are illustrated for vertically polarized plane waves obliquely incident on the layer of cylinders. The NMM3D results for the extended-cylinder case show large differences of transmission from the results of the other approaches, such as the effective permittivity (EP), the distorted Born approximation (DBA), and the radiative transfer equation (RTE). For the case of short cylinders, the NMM3D results are in close agreement with those of EP, DBA, and RTE.
TL;DR: In this paper, it is proved that the translation invariance property of the phaseless far-field pattern can indeed be broken if superpositions of two plane waves are used as the incident fields for all wave numbers in a finite interval.
TL;DR: In this paper, a radial/azimuthal polarization converter (S-wave plate) placed near the focal plane of the lens is used to create three interfering plane waves and the interference pattern is found to host C-points and V-points in a hexagonal lattice.
TL;DR: In this article, the effect of lateral shift between layers is considered and closed-form expressions for the equivalent layer reactance are derived for the higher order interaction between shifted layers, which can be used to derive an equivalent circuit model that describes the scattering parameters of a plane wave impinging on a slab composed by an arbitrary finite number of metal layers.
Abstract: In this paper, we present analytical models to describe artificial dielectric layers (ADLs), when a lateral shift between layers is present. The alternate lateral displacement between layers is an important parameter to engineer the desired effective electromagnetic properties of the equivalent homogeneous material realized with the ADLs. More specifically, the equivalent dielectric constants that can be realized by alternatively shifting the layers are higher compared with the aligned case. Closed-form expressions are derived for the equivalent layer reactance that includes the higher order interaction between shifted layers. The given analytical formulas can be used to derive an equivalent circuit model that describes the scattering parameters of a plane wave impinging on a slab composed by an arbitrary finite number of metal layers. To aid the design of artificial dielectric slabs, the effective permittivity and permeability tensors are also retrieved from the scattering parameters.
TL;DR: In this paper, a constitutive equation and a governing equation for in-plane wave propagation in viscoelastic monolayer graphene were developed by employing Hamilton's principle and nonlocal strain gradient theory.
Abstract: The behaviors of monolayer graphene sheet have attracted increasing attention of many scientists and researchers. In this study, the propagation behaviors of in-plane wave in viscoelastic monolayer graphene are investigated. The constitutive equation and governing equation for in-plane wave propagation is developed by employing Hamilton’s principle and nonlocal strain gradient theory. By solving the governing equation of motion, the closed-form dispersion relation between phase velocity and wave number is derived and an asymptotic phase velocity can be acquired. The effects of wave number, material length scale parameter, nonlocal parameter and damping coefficient on in-plane wave propagation behaviors are discussed in the numerical studies. It is found that, when exciting wavelengths or structural dimensions become comparable to the material length scale parameters and nonlocal parameters, the scaling effects on wave propagation behaviors are significant. For nanoscaled graphene sheet, the effects of nonlocal parameter, material length scale parameter and damping coefficient on phase velocity are tiny at low wave numbers while significant at high wave numbers. The phase velocity would increase with the increase of material length scale parameter or the decrease of nonlocal parameter and damping coefficient. Furthermore, results indicate that the asymptotic phase velocity can be increase by increasing material length scale parameter or decreasing nonlocal parameter.