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Showing papers on "Plane wave published in 2015"


Journal ArticleDOI
TL;DR: It is shown that spin–orbit coupling, when the spin of the incident circularly polarized light is converted into lateral electromagnetic momentum, leads to a lateral optical force acting on particles placed above a substrate, associated with a recoil mechanical force.
Abstract: Optical forces allow manipulation of small particles and control of nanophotonic structures with light beams. While some techniques rely on structured light to move particles using field intensity gradients, acting locally, other optical forces can 'push' particles on a wide area of illumination but only in the direction of light propagation. Here we show that spin-orbit coupling, when the spin of the incident circularly polarized light is converted into lateral electromagnetic momentum, leads to a lateral optical force acting on particles placed above a substrate, associated with a recoil mechanical force. This counterintuitive force acts in a direction in which the illumination has neither a field gradient nor propagation. The force direction is switchable with the polarization of uniform, plane wave illumination, and its magnitude is comparable to other optical forces.

176 citations


Journal ArticleDOI
TL;DR: It is shown, both theoretically and experimentally, that full-power reflection with general control over the reflected wave phase is possible with a single-layer array of deeply subwavelength inclusions, and it is proved that it is possible using electrically and magnetically polarizable inclusions.
Abstract: Conventional mirrors obey the simple reflection law that a plane wave is reflected as a plane wave, at the same angle. To engineer spatial distributions of fields reflected from a mirror, one can either shape the reflector or position some phase-correcting elements on top of a mirror surface. Here we show, both theoretically and experimentally, that full-power reflection with general control over the reflected wave phase is possible with a single-layer array of deeply subwavelength inclusions. These proposed artificial surfaces, metamirrors, provide various functions of shaped or nonuniform reflectors without utilizing any mirror. This can be achieved only if the forward and backward scattering of the inclusions in the array can be engineered independently, and we prove that it is possible using electrically and magnetically polarizable inclusions. The proposed subwavelength inclusions possess desired reflecting properties at the operational frequency band, while at other frequencies the array is practically transparent. The metamirror concept leads to a variety of applications over the entire electromagnetic spectrum, such as optically transparent focusing antennas for satellites, multifrequency reflector antennas for radio astronomy, low-profile conformal antennas for telecommunications, and nanoreflectarray antennas for integrated optics.

166 citations


Journal ArticleDOI
TL;DR: Using the refractive index spectrum of oceanic turbulence under weak turbulence conditions, analysis of the aperture-averaged scintillation index is carried out, for a horizontally propagating plane wave and spherical wave, the associated probability of fade, mean signal-to-noise ratio, and mean bit error rate are analyzed.
Abstract: In clean ocean water, the performance of a underwater optical communication system is limited mainly by oceanic turbulence, which is defined as the fluctuations in the index of refraction resulting from temperature and salinity fluctuations. In this paper, using the refractive index spectrum of oceanic turbulence under weak turbulence conditions, we carry out, for a horizontally propagating plane wave and spherical wave, analysis of the aperture-averaged scintillation index, the associated probability of fade, mean signal-to-noise ratio, and mean bit error rate. Our theoretical results show that for various values of the rate of dissipation of mean squared temperature and the temperature-salinity balance parameter, the large-aperture receiver leads to a remarkable decrease of scintillation and consequently a significant improvement on the system performance. Such an effect is more noticeable in the plane wave case than in the spherical wave case.

163 citations


Journal ArticleDOI
20 Feb 2015-Science
TL;DR: This work highlights that, even in free space, the invariance of the speed of light only applies to plane waves, and shows a reduction in the group velocity of photons in both a Bessel beam and photons in a focused Gaussian beam.
Abstract: That the speed of light in free space is constant is a cornerstone of modern physics. However, light beams have finite transverse size, which leads to a modification of their wave vectors resulting in a change to their phase and group velocities. We study the group velocity of single photons by measuring a change in their arrival time that results from changing the beam’s transverse spatial structure. Using time-correlated photon pairs, we show a reduction in the group velocity of photons in both a Bessel beam and photons in a focused Gaussian beam. In both cases, the delay is several micrometers over a propagation distance of ~1 meter. Our work highlights that, even in free space, the invariance of the speed of light only applies to plane waves.

142 citations


Book
10 Sep 2015
TL;DR: In this paper, a modified Watson transformation is applied to the amplitude of a scalar plane wave by a totally reflecting sphere (hardcore potential) at high frequencies, and the behavior of the solution both in near and far regions of space is discussed, as well as the accuracy and domain of applicability of the WKB approximation and classical diffraction theory.
Abstract: The scattering of a scalar plane wave by a totally reflecting sphere (hardcore potential) at high frequencies is treated by a modified Watson transformation. The behavior of the solution both in the near and far regions of space is discussed, as well as the accuracy and domain of applicability of the WKB approximation and classical diffraction theory. It is shown that different transformations are required in the forward and backward half-spaces, and corresponding integral representations for the primary wave are derived. The transformations are rigorously proved and the convergence of the residue series is discussed. In the shadow region, the physical interpretation of the complex angular momentum poles in terms of surface waves is in agreement with Keller's geometrical theory of diffraction. In the lit region, sufficiently far from the shadow boundary, the WKB expansion for the wave function is confirmed up to the second order. On the surface of the sphere, Kirchhoff's approximation is accurate, except in the penumbra region, where the behavior is described by Fock's function. The diffraction effects in the neighborhood of the shadow boundary are investigated and the corrections to classical diffraction theory are obtained. The shift of the shadow boundary is evaluated. The expression for the wave function in the Fresnel-Lommel region is derived and applied to the discussion of the Poisson spot and the behavior near the axis. The total scattering amplitude is evaluated for all angles, including the neighborhood of the forward and backward directions. The corrections to the forward diffraction peak and the transition to the region of geometrical reflection are discussed. The modified Watson transformation is also applied directly to the scattering amplitude. The connection between representations valid in different regions is established.

137 citations


Journal ArticleDOI
TL;DR: A whole class of waves that have constant intensity in the presence of linear as well as of nonlinear inhomogeneous media with gain and loss are presented to study the fundamental phenomenon of modulation instability in an inhomogeneity environment.
Abstract: In the presence of a Hermitian potential, a plane wave propagating in free space cannot maintain a constant intensity due to scattering. Here, Makris et al. show that in non-Hermitian potential, waves can propagate with constant intensity through linear and nonlinear inhomogeneous media with gain and loss.

130 citations


Journal ArticleDOI
TL;DR: The results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion.
Abstract: The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectron wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. The results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion.

124 citations


Journal ArticleDOI
TL;DR: 3-D SWE based on ultrafast volumetric imaging in a clinically applicable configuration is demonstrated based on a 32 × 32 matrix phased array driven by a customized, programmable, 1024-channel ultrasound system to perform 4-D shear-wave imaging.
Abstract: Over the last ten years, shear wave elastography (SWE) has seen considerable development and is now routinely used in clinics to provide mechanical characterization of tissues to improve diagnosis. The most advanced technique relies on the use of an ultrafast scanner to generate and image shear waves in real time in a 2-D plane at several thousands of frames per second. We have recently introduced 3-D ultrafast ultrasound imaging to acquire with matrix probes the 3-D propagation of shear waves generated by a dedicated radiation pressure transducer in a single acquisition. In this study, we demonstrate 3-D SWE based on ultrafast volumetric imaging in a clinically applicable configuration. A 32 × 32 matrix phased array driven by a customized, programmable, 1024-channel ultrasound system was designed to perform 4-D shear-wave imaging. A matrix phased array was used to generate and control in 3-D the shear waves inside the medium using the acoustic radiation force. The same matrix array was used with 3-D coherent plane wave compounding to perform high-quality ultrafast imaging of the shear wave propagation. Volumetric ultrafast acquisitions were then beamformed in 3-D using a delay-and-sum algorithm. 3-D volumetric maps of the shear modulus were reconstructed using a time-of-flight algorithm based on local multiscale cross-correlation of shear wave profiles in the three main directions using directional filters. Results are first presented in an isotropic homogeneous and elastic breast phantom. Then, a full 3-D stiffness reconstruction of the breast was performed in vivo on healthy volunteers. This new full 3-D ultrafast ultrasound system paves the way toward real-time 3-D SWE.

92 citations


Journal ArticleDOI
TL;DR: The Fast Irregular Antenna Field Transformation Algorithm (FIAFTA) as discussed by the authors is a spectral domain representation of irregular field transformations with propagating plane waves on the Ewald sphere.
Abstract: Electromagnetic field transformations are important for electromagnetic simulations and for measurements. Especially for field measurements, the influence of the measurement probe must be considered, and this can be achieved by working with weighted field transformations. This paper is a review paper on weighted field transformations, where new information on algorithmic properties and new results are also included. Starting from the spatial domain weighted radiation integral involving free space Green's functions, properties such as uniqueness and the meaning of the weighting function are discussed. Several spectral domain formulations of the weighted field transformation integrals are reviewed. The focus of the paper is on hierarchical multilevel representations of irregular field transformations with propagating plane waves on the Ewald sphere. The resulting Fast Irregular Antenna Field Transformation Algorithm (FIAFTA) is a versatile and efficient transformation technique for arbitrary antenna and scattering fields. The fields can be sampled at arbitrary irregular locations and with arbitrary measurement probes without compromising the accuracy and the efficiency of the algorithm. FIAFTA supports different equivalent sources representations of the radiation or scattering object: 1) equivalent surface current densities discretized on triangular meshes, 2) plane wave representations, 3) spherical harmonics representations. The current densities provide for excellent spatial localization and deliver most diagnostics information about the test object. A priori information about the test object can easily be incorporated, too. Using plane wave and spherical harmonics representations, the spatial localization is not as good as with spatial current densities, but still much better than in the case of conventional modal expansions. Both far-field based expansions lead to faster transformations than the equivalent currents and in particular the orthogonal spherical harmonics expansion is a very attractive and robust choice. All three expansions are well-suited for efficient echo suppression by spatial filtering. Various new field transformation and new computational performance results are shown in order to illustrate some capabilities of the algorithm.

90 citations


Journal ArticleDOI
TL;DR: This work introduces multiplane wave imaging, a new method that strongly improves ultrafast images signal-to-noise ratio by virtually increasing the emission signal amplitude without compromising the frame rate.
Abstract: Ultrafast imaging using plane or diverging waves has recently enabled new ultrasound imaging modes with improved sensitivity and very high frame rates. Some of these new imaging modalities include shear wave elastography, ultrafast Doppler, ultrafast contrast-enhanced imaging and functional ultrasound imaging. Even though ultrafast imaging already encounters clinical success, increasing even more its penetration depth and signal-to-noise ratio for dedicated applications would be valuable. Ultrafast imaging relies on the coherent compounding of backscattered echoes resulting from successive tilted plane waves emissions; this produces high-resolution ultrasound images with a trade-off between final frame rate, contrast and resolution. In this work, we introduce multiplane wave imaging, a new method that strongly improves ultrafast images signal-to-noise ratio by virtually increasing the emission signal amplitude without compromising the frame rate. This method relies on the successive transmissions of multiple plane waves with differently coded amplitudes and emission angles in a single transmit event. Data from each single plane wave of increased amplitude can then be obtained, by recombining the received data of successive events with the proper coefficients. The benefits of multiplane wave for B-mode, shear wave elastography and ultrafast Doppler imaging are experimentally demonstrated. Multiplane wave with 4 plane waves emissions yields a 5.8 ± 0.5 dB increase in signal-to-noise ratio and approximately 10 mm in penetration in a calibrated ultrasound phantom (0.7 d MHz(-1) cm(-1)). In shear wave elastography, the same multiplane wave configuration yields a 2.07 ± 0.05 fold reduction of the particle velocity standard deviation and a two-fold reduction of the shear wave velocity maps standard deviation. In functional ultrasound imaging, the mapping of cerebral blood volume results in a 3 to 6 dB increase of the contrast-to-noise ratio in deep structures of the rodent brain.

85 citations


Proceedings ArticleDOI
01 Dec 2015
TL;DR: This paper proposes an analytical spherical-wave channel model for large linear arrays, which is also compatible with conventional planewave models, and investigates how MSs can be spatially separated in simple line-of-sight (LoS) scenarios.
Abstract: Massive MIMO is considered a key technology for the future wireless communication systems. The promising properties in terms of higher spectral and transmit-energy efficiency are brought by the large number of antennas at the base station(BS). As the number of antennas increases, the aperture of the BS antenna array may become much larger, as compared to today's antenna arrays. In this case, mobile stations (MSs) and significant scatterers can locate inside the Rayleigh distance of large arrays, and spherical wavefronts rather than planar wavefronts are experienced over the arrays. In this paper, we propose an analytical spherical-wave channel model for large linear arrays, which is also compatible with conventional planewave models. Based on the spherical- wave model, we investigate how MSs can be spatially separated in simple line-of-sight (LoS) scenarios. The results theoretically explain the observation in experiments that spherical wavefronts help decorrelate the MS channels more effectively than planar wavefronts.

Journal ArticleDOI
TL;DR: In this paper, bound states in the radiation continuum (BSC) in a linear periodic array of dielectric spheres in air above the light cone were demonstrated. But the results were limited to the case where the radius of the spheres is bounded by a constant.
Abstract: We demonstrate bound states in the radiation continuum (BSC) in a linear periodic array of dielectric spheres in air above the light cone. We classify the BSCs by orbital angular momentum m = 0,±1,±2 according to the rotational symmetry of the array, Bloch wave vector ꞵ directed along the array according to the translational symmetry, and polarization. The most simple symmetry protectedBSCshavem = 0,ꞵ = 0 and occur in a wide range of the radius of the spheres and dielectric constant. More sophisticated BSCs with m 6= 0,ꞵ = 0 exist only for a selected radius of spheres at fixed dielectric constant. We also find robust Bloch BSCs with ꞵ 6= 0,m = 0. All BSCs reside within the first but below the other diffraction continua. We show that the BSCs can be easily detected by bright features in scattering of different plane waves by the array as dependent on type of the BSC. The symmetry protected TE/TMBSCs can be traced by collapsing Fano resonance in cross-sections of normally incident TE/TM plane waves. When plane wave with circular polarization with frequency tuned to the bound states with OAM illuminates the array the spin angular momentum of the incident wave transfers into the orbital angular momentum of the BSC.This ,inturn, gives rise to giant vortical power currents rotating around the array. Incident wave with linear polarization with frequency tuned to the Bloch bound state in the continuum induces giant laminar power currents. At last, the plane wave with linear polarization incident under tilt relative to the axis of array excites Poynting currents spiralling around the array. It is demonstrated numerically that quasi-bound leaky modes of the array can propagate both stationary waves and light pulses to a distance of 60 wavelengths at the frequencies close to the bound states in the radiation continuum. A semi-analytical estimate for decay rates of the guided waves is found to match the numerical data to a good accuracy.

Journal ArticleDOI
TL;DR: In this article, a surface wave antenna with a probe-fed parallel plate waveguide with a modified parabolic reflecting wall and a metallic post is proposed to transform the cylindrical wave to a unidirectional plane wave within a broad frequency range.
Abstract: This paper presents the design of a compact and wideband surface wave antenna that exhibits very low profile and can be flush-mounted on a conformal platform. The proposed antenna comprises a tapered grounded ceramic slab, a unidirectional surface wave launcher, and a tapered impedance transition. The ceramic slab is smoothly tapered to transform the guided surface wave into radiated space wave over a wide frequency range. The surface wave launcher employs a probe-fed parallel plate waveguide with a modified parabolic reflecting wall and a metallic post, which are critical for effectively transforming the cylindrical waves to a unidirectional plane wave within a broad frequency range. Simulated results show that the proposed surface wave antenna achieves a wide operation bandwidth from 6.1 to 18 GHz with a thickness of only ${\bf 0}.{\bf 12}{\lambda _0}$ at the center frequency. Acceptable gain values with stable and quasi end-fire radiation beams are obtained over the entire frequency band. A prototype of the proposed antenna is fabricated and tested. Measured results are in good agreement with simulated ones.

Journal ArticleDOI
TL;DR: In this paper, different integral equation formulations of the problem are investigated, with special attention paid to the stability properties of the resulting system matrix, and the stability of the system matrix is analyzed in terms of the surface impedance boundary condition.
Abstract: Metasurfaces are thin metamaterial layers characterized by unusual dispersion properties of surface/guided wave and/or reflection properties of otherwise incident plane waves. At the scales intervening in their design, metasurfaces can be described through a surface impedance boundary condition. The impedance, possibly tensorial, is often “modulated,” i.e., it can vary from place to place on the surface (by design). We investigate on different integral equation formulations of the problem, with special attention to the stability properties of the resulting system matrix.

Journal ArticleDOI
TL;DR: In this paper, a first-principles approach is used to study the structural, electronic and magnetic properties of Sr2GdReO6, using full-potential linearized augmented plane wave (FP-LAPW) method within the spin density functional theory.

Journal ArticleDOI
Ben King1
TL;DR: In this paper, the two-photon emission of an electron in an electromagnetic plane wave of vanishing frequency is calculated, and the unpolarized probability is split into a two-step process, which is shown to be exactly equal to an integration over polarized subprocesses.
Abstract: Two-photon emission of an electron in an electromagnetic plane wave of vanishing frequency is calculated. The unpolarized probability is split into a two-step process, which is shown to be exactly equal to an integration over polarized subprocesses, and a one-step process, which is found to be dominant over the formation length. The assumptions of neglecting spin and simultaneous emission, commonly used in numerical simulations, are discussed in light of these results.

Journal ArticleDOI
TL;DR: In this article, a simple acoustic metasurface is designed and characterized, whose microstructure is constructed with a cavity filled with air and two elastic membranes on the ends of cavity.
Abstract: Nowadays, the acoustic devices are developing toward miniaturization. However, conventional materials can hardly satisfy the requirements because of their large size and complex manufacturing process. The introduction of acoustic metasurfaces has broken these restrictions, as they are able to manipulate sound waves at will by utilizing ultrathin planar metamaterials. Here, a simple acoustic metasurface is designed and characterized, whose microstructure is constructed with a cavity filled with air and two elastic membranes on the ends of cavity. By appropriately optimizing the configurations of microstructures, the steering of transmitted wave trajectory is demonstrated, and some extraordinary phenomena are realized at 3.5 kHz, such as planar acoustic axicon, acoustic lens, the conversion from spherical waves to plane waves, and the transformation from propagating waves to surface waves.

Journal ArticleDOI
TL;DR: A compact quasi-optical setup based on conventional rectangular horn antennas and two symmetrical parabolic mirrors is designed to provide a plane wave on the material under test and the complex permittivity is presented together with a detailed uncertainty budget.
Abstract: A compact quasi-optical setup based on conventional rectangular horn antennas and two symmetrical parabolic mirrors is designed to provide a plane wave on the material under test. To measure the scattering parameters at millimeter/submillimeter wavelengths, a commercial vector network analyzer and waveguide frequency extension units are used. The calibration of the system is performed with a simple practical deembedding process to determine the S-parameters on the material surface without using high-cost micrometer positioners. A reliable extraction method is presented to derive the material permittivity and calculate the errors and uncertainties as direct functions of the sample and setup geometry and their physical characteristics. Several materials are measured and the complex permittivity is presented together with a detailed uncertainty budget.

Journal ArticleDOI
TL;DR: The ultra-thin optical vortex phase plate (VPP) was designed and investigated based on the metasurface of the metal rectangular split-ring resonators (MRSRRs) array as mentioned in this paper.
Abstract: The ultra-thin optical vortex phase plate (VPP) has been designed and investigated based on the metasurface of the metal rectangular split-ring resonators (MRSRRs) array. The circularly polarized incident light can convert into corresponding cross-polarization transmission light, and the phase and the amplitude of cross-polarization transmission light can be simultaneously governed by modulating two arms of the MRSRR. The MRSRR has been arranged in a special order for forming an ultra-thin optical VPP that can covert a plane wave into a vortex beam with a variety of the topological charges, and the transformation between spin angular momentum (SAM) and orbital angular momentum (OAM) has been discussed in detail. The multi-spectral characteristics of the VPP have also been investigated, and the operating bandwidth of the designed VPP is 190 nm (in the range of 710–900 nm), which enable a potential implication for integrated optics and vortex optics.

Journal ArticleDOI
TL;DR: In this paper, the angular-resolved photoemission spectra (ARPES) from a number of polycyclic aromatic hydrocarbons and graphene were analyzed using ab-initio density functional theory and the one-step model where the matrix element was simplified by assuming a plane wave for the final state.

Journal ArticleDOI
TL;DR: In vivo applications of the transverse oscillation method on the common carotid and the brachial arteries are presented and overall biases lower than 20% when varying the beam-to-flow angle, the peak velocity, and the depth of interest are presented.
Abstract: Transverse oscillation (TO) methods introduce oscillations in the pulse–echo field (PEF) along the direction transverse to the ultrasound propagation direction. This may be exploited to extend flow investigations toward multidimensional estimates. In this paper, the TOs are coupled with the transmission of plane waves (PWs) to reconstruct high-framerate RF images with bidirectional oscillations in the pulse–echo field. Such RF images are then processed by a 2-D phase-based displacement estimator to produce 2-D vector flow maps at thousands of frames per second. First, the capability of generating TOs after PW transmissions was thoroughly investigated by varying the lateral wavelength, the burst length, and the transmission frequency. Over the entire region of interest, the generated lateral wavelengths, compared with the designed ones, presented bias and standard deviation of −3.3 ± 5.7% and 10.6 ± 7.4% in simulations and experiments, respectively. The performance of the ultrafast vector flow mapping method was also assessed by evaluating the differences between the estimated velocities and the expected ones. Both simulations and experiments show overall biases lower than 20% when varying the beam-to-flow angle, the peak velocity, and the depth of interest. In vivo applications of the method on the common carotid and the brachial arteries are also presented.

Journal ArticleDOI
TL;DR: In this paper, the formation of a photonic jet is demonstrated using the recently proposed 3D dielectric cuboids working in the "reflection" mode when the specific, spatially localized region is localized in the direction of the incident wavefront.
Abstract: A photonic jet (a terajet at terahertz frequencies) commonly denotes a specific, spatially localized region in the near field on the front side of a dielectric particle with a diameter comparable with the wavelength illuminated by a plane wave on its back side (i.e., the jet emerges from the shadow surface of a dielectric particle). In this Letter, the formation of a photonic jet is demonstrated using the recently proposed three-dimensional (3D) dielectric cuboids working in the "reflection" mode when the specific, spatially localized region is localized in the direction of the incident wavefront. The results of the simulations based on the Finite Integration Technique are discussed. All dimensions are given in wavelength units so that all results can be scaled to any frequency of interest, including optical frequencies, thus simplifying the fabrication process compared with spherical dielectrics. The results presented here may be of interest for novel applications, including microscopy techniques and sensors.

Journal ArticleDOI
TL;DR: In this paper, a numerical dispersion analysis for the linear two-dimensional elastodynamics equations approximated by means of NURBS-based Isogeometric Analysis in the framework of the Galerkin method is carried out.

Journal ArticleDOI
TL;DR: In this paper, a solution of the paraxial Helmholtz equation that describes a family of three-dimensional and two-dimensional form-invariant half-Pearcey beams (HP-beams) was obtained.
Abstract: We obtain a new solution of the paraxial Helmholtz equation that describes a family of three-dimensional and two-dimensional form-invariant half-Pearcey beams (HP-beams). HP-beams generalize Pearcey beams obtained in Ring et al (2012) Opt. Express 20 18955, since these Pearcey beams can be considered as the sum of two first-order HP-beams. Three-dimensional HP-beams have angular spectra of plane waves, which are non-zero at a half parabola. For functions of HP-beam complex amplitudes, the orthogonality properties have been revealed. Using a spatial phase modulator, we generated superposition of HP-beams. For two-dimensional HP-beam acceleration and deceleration of trajectory has been shown for areas before and beyond the focal plane respectively.

Journal ArticleDOI
TL;DR: In this paper, an analysis of scattering of an electromagnetic linearly polarized plane wave by a multilayered sphere is presented, where the focus is on obtaining a computational form of the Mie coefficients for the scattered field.
Abstract: An analysis is presented of scattering of an electromagnetic linearly polarized plane wave by a multilayered sphere. The focus is on obtaining a computational form of the Mie coefficients for the scattered field. A central role is played by ratios of spherical Bessel functions that can be calculated easily, rapidly, and accurately by recurrence relations whose stabilities are demonstrated. Logarithmic derivatives are not employed. A detailed outline is given of a carefully tested computer program for implementing and validating the analysis. Numerous comparisons are given of numerical results obtained with this program with corresponding results in the literature. Important properties of the Mie coefficients and aspects of the scattered field are discussed including the loci of the Mie coefficients in the complex plane; the resonances of the Mie coefficients; the extinction, scattering, and absorption efficiencies of the scattered field; radiation pressure; the Debye series, and the complex angular momentum (CAM) method.

Journal ArticleDOI
TL;DR: In this article, the results of a combined experimental and numerical study of the generation of internal waves using the novel internal wave generator design of Gostiaux et al. were presented.
Abstract: We present the results of a combined experimental and numerical study of the generation of internal waves using the novel internal wave generator design of Gostiaux et al. (2007). This mechanism, which involves a tunable source comprised of oscillating plates, has so far been used for a few fundamental studies of internal waves, but its full potential has yet to be realized. Our studies reveal that this approach is capable of producing a wide variety of two-dimensional wave fields, including plane waves, wave beams and discrete vertical modes in finite-depth stratifications. The effects of discretization by a finite number of plates, forcing amplitude and angle of propagation are investigated, and it is found that the method is remarkably efficient at generating a complete wave field despite forcing only one velocity component in a controllable manner. We furthermore find that the nature of the radiated wave field is well predicted using Fourier transforms of the spatial structure of the wave generator.

Journal ArticleDOI
TL;DR: In this paper, a two-dimensional periodic pile barrier system was proposed, which can produce low-frequency or middle-frequency attenuation zones (AZs). Periodic pile barriers are composed of periodically arranged hollow piles filled with either soft or hard in-fill materials.
Abstract: The frequency dispersion characteristics of pile barriers are receiving more attention due to their effectiveness and a better understanding of their behavior at attenuating middle and lower frequency ground vibrations. Based on a comprehensive study, this paper proposes a two-dimensional periodic pile barrier system, which can produce low-frequency or middle-frequency attenuation zones (AZs). Periodic pile barriers are composed of periodically arranged hollow piles filled with either soft or hard in-fill materials. Finite element method and plane wave expansion method are first used to study dispersion curves, AZs, and corresponding wave dispersion mechanisms. Influencing factors of the periodic pile barrier on the AZs are then identified based on a parametric study. To further illustrate the effectiveness of the vibration attenuation, a three-dimensional pile–soil finite element model with combined periodic pile barriers is analyzed, and the frequency ranges of vibration reduction are found to b...

Journal ArticleDOI
TL;DR: The theory and implementation of this MTS transformation allows for a deformation of the SW wavefront which addresses the local wavevector along not-rectilinear paths and can be analysed in the framework of transformation optics.
Abstract: Metasurfaces (MTSs) constitute a class of thin metamaterials used for controlling plane waves and surface waves (SWs). At microwave frequencies, they are constituted by a metallic texture with elements of sub-wavelength size printed on thin grounded dielectric substrates. These structures support the propagation of SWs. By averaging the tangential fields, the MTSs can be characterized through homogenized isotropic or anisotropic boundary conditions, which can be described through a homogeneous equivalent impedance. This impedance can be spatially modulated by locally changing the size/orientation of the texture elements. This allows for a deformation of the SW wavefront which addresses the local wavevector along not-rectilinear paths. The effect of the MTS modulation can be analysed in the framework of transformation optics. This article reviews theory and implementation of this MTS transformation and shows some examples at microwave frequencies.

Journal ArticleDOI
TL;DR: This study presents an exact, analytic expression for the two-dimensional Fourier transform description of shear wave propagation in viscoelastic materials following asymmetric Gaussian excitations and uses this expression to evaluate the bias in 2D-FT measurements obtained using the plane or cylindrical wave assumptions.
Abstract: Recent measurements of shear wave propagation in viscoelastic materials have been analyzed by constructing the two-dimensional Fourier transform (2D-FT) of the spatial-temporal shear wave signal and using an analysis procedure derived under the assumption the wave is described as a plane wave, or as the asymptotic form of a wave expanding radially from a cylindrically symmetric source. This study presents an exact, analytic expression for the 2D-FT description of shear wave propagation in viscoelastic materials following asymmetric Gaussian excitations and uses this expression to evaluate the bias in 2D-FT measurements obtained using the plane or cylindrical wave assumptions. A wide range of biases are observed depending on specific values of frequency, aspect ratio R of the source asymmetry, and material properties. These biases can be reduced significantly by weighting the shear wave signal in the spatial domain to correct for the geometric spreading of the shear wavefront using a factor of x(p). The optimal weighting power p is found to be near the theoretical value of 0.5 for the case of a cylindrical source with R = 1, and decreases for asymmetric sources with R > 1.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the ARW method for full-potential electronic structure calculations and presented an error analysis for both linear Schrodinger type equations and nonlinear Kohn−Sham equations.
Abstract: This paper investigates the augmented plane wave methods which are widely used in full-potential electronic structure calculations. These methods introduce basis functions that describe different regions using different discretization schemes. We construct a nonconforming method based on this idea and present an a priori error analysis for both linear Schrodinger type equations and nonlinear Kohn−Sham equations. Some numerical experiments are presented to support our theory.