Incident Plane Research Articles

Bound States and Scattering of Magnons on a Superconducting Vortex in Ferromagnet-superconductor Heterostructures

We study the magnon spectrum in a thin ferromagnetic-superconductor heterostructure in the presence of a single superconducting vortex. We employ the Bogolubov–de Gennes Hamiltonian which describes the magnons in the presence of the stray magnetic field and the non-uniform magnetic texture induced by the vortex. We find that the vortex localizes magnon states approximately in the same way as a charge center produces electron bound states due to screened Coulomb interaction in the two-dimensional electron gas. The number of these localized states is substantially determined by the material parameters of the ferromagnetic film only. We solve the scattering problem for an incident plane spin wave and compute the total and transport cross sections. We demonstrate that the vortex-induced non-uniform magnetic texture in chiral ferromagnetic film produces a skew scattering of magnons. We explore the peculiarities of the quantum scattering problem that correspond to orbiting in the classical limit.

Fractional-order hybridly polarized vector beams: generation, focusing, propagation, and spatial self-phase modulation

As a class of integer-order vector beams, hybridly polarized vector beams (HPVBs) are widely used in focus shaping, femtosecond laser filamentation, linear and nonlinear polarization evolution, etc. Recently, fractional-order vector beams have gained widespread interest due to their more control parameters, rich photophysical properties, and novel nonlinear optical phenomena. In this work, we report the experimental generation, focusing and propagation characteristics, and spatial self-phase modulation (SSPM) phenomenon of fractional-order HPVBs. It is shown that during the focusing and propagation processes, the intensity pattern of fractional-order HPVBs develops from a near-Gaussian structure in the incident plane to an asymmetric structure in both the focal field and the far field. Meanwhile, their distributions of state of polarization (SoP) also evolve, although it remains a hybrid polarization distribution overall. When the focused fractional-order HPVBs pass through the nonlinear optical sample, the far-field self-diffraction intensity pattern displays an irregular concentric multi-ring structure with a hybrid polarization distribution. It is found that the nonlinear medium not only modulates the far-field intensity pattern of fractional-order HPVBs but also controls their SoP distribution. This symmetric breaking HPVB has potential application prospects in optical micro-manipulation, light-matter interaction, optical spin-orbit conversion, etc.

Nonlinear vibro-acoustic analysis of an axially moving submerged circular cylindrical shell

In this study, the nonlinear vibro-acoustic dynamics and stability of doubly-clamped axially moving cylindrical shell are investigated. The exterior surface of the shell is in contact with fluid and subjected to oblique incident plane sound wave. Donnell’s nonlinear shallow shell theory is used to derive the nonlinear partial differential equation of the cylindrical shell for the radial motion. The Galerkin method is employed to discretize the equations of motion into the set of coupled nonlinear nonhomogeneous ordinary second order differential equations. Considering both driven and companion modes, Multiple Scales Method is used to obtain the response of the system. The effects of sound level, incident angle and axially velocity on the frequency response of the system are studied. The results show that, with increase in the shell velocity transmission loss of the circular shell increases. In addition, at low shell axial velocities simultaneous excitation of the driven and companion modes occurs.

Surface resonance enhanced Goos–Hänchen shifts for different orientations of antiferromagnets in the presence of an applied magnetic field

When reflection takes place off the surface of antiferromagnets, surface resonances, considered as an extension of surface polariton dispersion curves into the reflection region, can enhance the lateral shift of the reflected beam in the presence of an external magnetic field. The effect was earlier studied for both the applied field and the antiferromagnet easy axis perpendicular to the plane of incidence in the case of a small applied field. Here, using MnF2 as the antiferromagnet, we extend the work to look at how increasing the field and changing the antiferromagnet orientation affects the results, which always display nonreciprocity. We find that, when the antiferromagnet easy axis is parallel to the surface within the plane of incidence, leading to spin canting, enhanced shifts in the reflection region occur in much the same way as when the easy axis is along the applied field direction, but an applied field an order of magnitude higher is needed. However, when the easy axis is perpendicular to the surface even higher fields are necessary, and it is difficult to achieve such enhanced shifts.

Effects of honeycomb panel's finite dimensions on acoustic performance for lightweight sound insulation

A honeycomb panel is considered as a lightweight sound insulation solution both numerically and experimentally. First, a unit cell with fixed and infinite periodic conditions is modeled, exhibiting high insulation levels up to the membrane's eigenfrequency. Closer to industrial applications, a numerical model is developed, where the fixed conditions are applied only on the sides of the finite honeycomb panel. Taking into account structural modes of longer wavelength with this configuration, the panel's first eigenfrequency occurs at lower frequency than the previous case, yielding to a reduced insulation power. Nevertheless, the low frequency performance obtained numerically on the honeycomb panel is validated with measurements under normal incidence plane waves and diffuse field excitations.

Experimental validation of anomalous acoustic wave refraction using Double layered acoustic gratings

Acoustic metasurfaces (AMSs) have garnered increasing attention over the past decade due to their remarkable capability for wave manipulation. AMSs have been widely applied in diverse domains, including anomalous refraction and extraordinary sound absorption/isolation, among others. However, typical AMS designs, such as Helmholtz resonator-like or labyrinthine structures, are often geometrically complex, limiting their practical usability. In this paper, we introduce an ultracompact Double Layered Acoustic Grating (DLAG) to achieve anomalous acoustic wave refraction. The DLAG comprises double-layered rigid panels with multiple perforated subwavelength slits. By optimizing the positions of these slits on the rigid panels, the acoustic energy of an obliquely incident plane wave can be concentrated within a predetermined region in an arbitrary direction. The paper will first review the theoretical background to predict the wave propagation controlled by DLAGs based on the surface coupling approach. Subsequently, the underlying principle to achieve anomalous refraction using DLAGs will be discussed. A 3D-printed DLAG with the optimized slit positions is used for demonstration. In the experiment, the acoustic energy of a plane wave with an incident angle of 36 degrees was successfully collimated within a predetermined focusing region with a negative refracted angle of -36 degrees.

On the focusing effect and interfacial evolution of incident shock waves impinging on double-layer nested heavy gas bubbles

A detailed numerical study about the planar incident shock wave impinging on heavy bubbles with different components and nested structures was conducted. Results show that the shock wave convergence occurs when the incident shock wave impinging on the pure SF6 bubble or CO2-SF6 nested bubbles, which triggers the shock wave focusing and obtains a high transient pressure. Changing the nested position and radius of the SF6 bubble in CO2-SF6 nested bubbles will change the interactional time and relative position of waves to affect the shock wave focusing time and peak pressure. Specifically, the shock wave focusing effect is enhanced, and the peak pressure is increased when the inner bubble is drifted downstream, high density, and larger sized. Thus, the later the shock wave focusing occurs, the higher the transient maximum pressure. The shock wave focusing process of double-layer nested bubbles is presented as follows: the new small shock wave (SS) formed by the intersection between the incident transmitted shock wave and the transmitted shock wave and another new shock wave formed by the collision of diffracted transmitted shock waves move in opposite directions to squeeze the undisturbed region and finally produce a high instantaneous pressure, where SS plays a major role in shock wave focusing. Further, the greater the intensity and velocity of focusing shock waves, the stronger the focusing effect and the higher the transient pressure.

Metasurface with two-dimensional gradient-index phase distribution constructed by rotation ellipse elements for backward RCS reduction

ABSTRACT In this letter, the realization of minimizing the scattering of the Ku band is investigated by designing a two-dimensional gradient-index metasurface to control the propagation of the incident waves. Through the gradient phase design, the maximum RCS reduction was observed at 14 GHz, the x-polarized plane wave exhibits an RCS reduction of 15.43 dB, while the y-polarized plane wave shows an RCS reduction of 13.13 dB compared to the same size of PEC. The proposed metasurface with low backward RCS shows the capability to scatter the incident plane wave in different directions at both normal and oblique incidence. According to equation 2, by calculating the variable phase distribution of large-scale arrays at different frequencies, the maximum reduction of RCS can be obtained at any frequencies. Therefore, this work effectively designs and suggests the research of low RCS metasurface at different frequencies.

Ultra-wide viewing angle holographic display system based on spherical diffraction

In the field of holographic displays, achieving a large viewing angle (LVA) has long been an essential and formidable challenge due to the limited diffraction angle of planar spatial light modulators (SLMs). Spherical holography, which allows observation from all perspectives, represents a practical approach to achieve the LVA. However, the physical limitations of commercial SLMs constrain direct implementation, making the realization of spherical holographic displays almost impractical and thus hindering technological advancement. This paper introduces an optical solution for spherical holographic display system, enabling the accurate reproduction of ultra-wide viewing angles and large objects. Our system utilizes a novel technique involving a convex parabolic mirror to convert an incident plane wave into a spherical wave. This innovative strategy permits the use of a planar SLM to create a 360°spherical holographic display. Additionally, we address the sampling issue for generating spherical holograms by constraining the point spread function (PSF), reducing the number of samples, and adapting it for visible light. Numerical simulations and optical experiments validate our success in achieving an ultra-wide viewing angle with a 360°horizontal angle and an 80°zenith angle range. Our system outperforms the state-of-the-art holographic-optical-elements approach both in computation speed and object size. We believe that our work significantly advances spherical holographic displays and offers a practical solution with vast potential applications in medicine, geology, and astronomy.

Polarization-independent quasi-BIC supported by non-rotationally symmetric dimer metasurfaces.

Asymmetric metasurfaces supporting quasi-bound states in the continuum (-BICs) have recently attracted significant interest in the field of nanophotonics due to their high quality factor and strong light-matter interaction properties. However, asymmetric metasurface structures are susceptible to the polarization state of the incident light, which constrains their potential applications. In this Letter, we present a new, to our knowledge, scheme of polarization-independent quasi-BIC resonance supported by a non-rotationally symmetric nanorod dimer metasurface. By tuning the asymmetry parameter, the designed metasurface exhibits a consistent quasi-BIC response for incident plane waves of arbitrary polarization. The physical mechanism of the quasi-BIC resonance is elucidated by the study of the far-field multipole decomposition and the near-field electromagnetic distribution. We then point out that the realization of the polarization-independent quasi-BIC resonance depends on the transition between magnetic and electric quadrupoles. Furthermore, the designed metasurface is demonstrated to have excellent refractive index sensing performance. This work provides a new idea for the design of polarization-independent and high-performance resonators.

A contactless in situ EFISH method for measuring electrostatic potential profile of semiconductor/electrolyte junctions.

In photoelectrochemical cells, promising devices for directly converting solar energy into storable chemical fuels, the spatial variation of the electrostatic potential across the semiconductor-electrolyte junction is the key parameter that determines the cell performance. In principle, electric field induced second harmonic generation (EFISH) provides a contactless in situ spectroscopic tool to measure the spatial variation of electrostatic potential. However, the total second harmonic generation (SHG) signal contains the contributions of the EFISH signals of semiconductor space charge layer and the electric double layer, in addition to the SHG signal of the electrode surface. The interference of these complex quantities hinders their analysis. In this work, to understand and deconvolute their contributions to the total SHG signals, bias-dependent SHG measurements are performed on the rutile TiO2(100)-electrolyte junction as a function of light polarization and crystal azimuthal angle (angle of the incident plane relative to the crystal [001] axis). A quadratic response between SHG intensity and the applied potential is observed in both the accumulation and depletion regions of TiO2. The relative phase difference and amplitude ratio are extracted at selected azimuthal angles and light polarizations. At 0° azimuthal angle and s-in-p-out polarization, the SHG intensity minimum has the best match with the TiO2 flatband potential due to the orthogonal relative phase difference between bias-dependent and bias-independent SHG terms. We further measure the pH-dependent flatband potential and probe the photovoltage under open circuit conditions using the EFISH technique, demonstrating the capability of this contactless method for measuring electrostatic potential at semiconductor-electrolyte junctions.

Solute segregation, clustering and interphase precipitation in Ti-Mo-Nb microalloyed steel studied by correlated electron backscattering diffraction and atom probe tomography

Site-specific atom probe tomography coupled with electron back scattering diffraction studies were used for the first time to elucidate the multi-element solute segregation and clustering at austenite-ferrite interface during early stages of phase transformation in Fe-Mn-Si-C steel alloyed with Ti, Mo and Nb. The results have shown the existence of negligible partitioning local equilibrium at interfaces with segregation of C, Mn, Ti and Mo to interfaces having the angle deviation in the range from 2.9 to 12° from Kurdjumov-Sacks orientation relationships (K-S ORs), but either irregular incident planes or the ones not following the matching according to K-S ORs. The segregation of Nb was less common, which was linked to the earlier occupancy of interfaces by Ti and Mo. Variation in solute segregation along the same interfaces is highlighted. Presence of clusters within and in close proximity to the interface is detected. The links between interface orientation, solute segregation, clustering and interphase precipitation are discussed.

Signatures of top versus bottom illuminations and their predicted implications for infrared transmission microspectroscopy.

Since both top and bottom illuminations are widely used in infrared transmission measurements, in this paper, we study the effects of different illuminations on the signatures in infrared microspectroscopy. By simulating a series of dielectric samples, we show that their extinction efficiency, , remains unchanged when the direction of the incident plane wave is reversed, even though the field distributions both inside and outside of the sample may be dramatically different. We find features in that are correlated with whispering gallery modes for one beam direction and correspond to completely different field distributions for the opposite beam direction. In addition, by linking the optical theorem and the reciprocity relation of far-field scattered field, we rigorously prove the invariance of for arbitrary dielectric targets under opposite plane-wave illuminations. Furthermore, we show the difference in the apparent absorbance spectrum for opposite beam directions when considering numerical apertures.

Improving the accuracy of measurement of bistatic scattering characteristics of material samples in various conf gurations

The infl uence of diffraction effects at the edges of fl at samples of small (2–4 wavelengths of incident wave) sizes on the results of measurements of the refl ection coeffi cient of the sample material, a bistatic characteristic that depends on the frequency of radiation in a wide (10–85°) range of incidence angles is considered. To reduce the infl uence of diffraction effects, samples of various confi gurations have been developed, made of magnetodielectric with frequency dispersion of dielectric and magnetic permeability. The samples are a metal plate, on one side of which the material under study is applied, and the other surfaces of the plate are covered with radiation-absorbent material. The scattering characteristics of samples of the developed confi gurations are numerically calculated and experimentally measured on a bistatic facility in an anechoic chamber. The experimental results correspond with the calculated data. A noticeable reduction in the infl uence of diffraction effects on the refl ectivity values in a wide angular and frequency range has been shown. Using numerical methods in the FEKO software package, the infl uence of the sample confi guration on the methodical error in refl ectance measurements was studied. It is shown that this error can be reduced by using a substrate of an extended shape in the plane of incidence (samples of a hybrid confi guration). The results obtained can be used to measure the scattering characteristics of materials in free space.

Unshielded facility testbed for electromagnetic wave attenuation using absorber slabs

AbstractThis paper presents a testbed for unshielded facilities utilizing planar electromagnetic absorbers. These slabs demonstrate comparable shielding effectiveness to that of reinforced concrete in the frequency range from 1 GHz to 6 GHz. The testbed serves as a platform for developing a measurement method to assess unshielded facilities. It can be configured with different materials that have various levels of shielding effectiveness. We evaluate the shielding effectiveness of the absorber slab and extract its electromagnetic parameters. The testbed is implemented in a semi‐anechoic chamber with inner dimensions of 3.00 × 3.06 × 2.50 m3. The electromagnetic wave attenuation for the unshielded facilities is defined as the ratio of received power within the assessment space relative to the incident power. The measurement results provide quantitative information on the attenuation of electromagnetic waves within unshielded facilities. The testbed configured with two types of incident planes is evaluated and compared with the mean attenuation and distribution characteristics.

Manipulation of Helicity-Dependent Photocurrent and Stokes Parameter Detection in Topological Insulator Bi2Te3 Nanowires.

Helicity-dependent photocurrent (HDPC) and its modulation in topological insulator Bi2Te3 nanowires have been investigated. It is revealed that when the incident plane of a laser is perpendicular to the nanowire, the HDPC is an odd function of the incident angle, which is mainly contributed by the circular photogalvanic effect originating from the surface states of Bi2Te3 nanowire. When the incident plane of a laser is parallel to the nanowire, the HDPC is approximately an even function of the incident angle, which is due to the circular photon drag effect coming from the surface states. It is found that the HDPC can be effectively tuned by the back gate and the ionic liquid top gate. By analyzing the substrate dependence of the HDPC, we find that the HDPC of the Bi2Te3 nanowire on the Si substrate is an order of magnitude larger than that on SiO2, which may be due to the spin injection from the Si substrate to the Bi2Te3 nanowire. In addition, by applying different biases, the Stokes parameters of a polarized light can be extracted by arithmetic operation of the photocurrents measured in the Bi2Te3 nanowire. This work suggests that topological insulator Bi2Te3 nanowires may provide a good platform for opto-spintronic devices, especially in chirality and polarimtry detection.

The role of the foundation flexibility on the seismic response of a modern tall building: Vertically incident plane waves

The soil-structure interaction (SSI) is an integral part of the seismic response of structures. The knowledge about its effects is based largely on numerical simulations involving simplified models. In this paper, we examine the consequence of several assumptions in SSI models of buildings, with emphasis on the rigid foundation assumption. To this end, we analyze several variants of a linear three-dimensional finite element model of the structure and soil corresponding to a uniquely instrumented 50-story skyscraper, with a basement on a pile foundation, located in southwest China. The models are excited by triaxial motion due to a vertically incident plane wave. The most realistic model (with basement and piles, both with bond contact with the soil), predicted an 8 % reduction of the apparent frequency and a 30 %–50 % increase in the apparent damping ratio of the 1st mode of vibration, relative to the model with fixed basement. The model with a rigid foundation (basement) embedded in the soil underestimated the reduction in apparent frequency by a factor of two. The SSI effects were the most pronounced for the model with flexible basement and no piles (16 %–19 % reduction in apparent frequency and 73 %–86 % increase in apparent damping ratio). The basement-structure interaction reduced the apparent frequency by 5 %–8 % depending on the direction. It is concluded that, for such a building, a detailed model of the structure and its foundation is needed to predict reliably the SSI effects.

Analytical solution to 2D dynamic soil-tunnel-building interaction under seismic SH-wave excitation considering the influence of the stiffness of tunnel and building's foundation

This investigation examines the structure-soil-structure interaction (SSSI) problem between a tunnel and nearby aboveground building, considering the impact of the stiffness of tunnel and building's foundation. A two-dimensional (2D) model is utilized, which includes a flexible circular tunnel and a three-story building anchored by a flexible semi-circular foundation embedded in a homogeneous half-space. The response of the system to incident plane SH-wave excitation is solved analytically using the wave function expansion method. The analysis focuses on how the system response is affected by the stiffness of the tunnel and the building's foundation. Tunnel stiffness plays a leading role in tunnel response analysis. The model with a rigid tunnel and rigid foundation can offer a reasonable system response overall, but it fails to accurately represent tunnel deformation and stress distribution. Depending on the stiffness of the building's foundation, the maximum value of the inter-story displacement of the first floor can be overestimated by around 70 %, with even greater overestimations for higher floors. The results help understand observed seismic behaviors and provide insight into the effects of foundation and tunnel stiffness on the tunnel-building interaction system.

To a dispersion law of an electromagnetic wave in a medium having a double anisotropy

Dispersion relations for a transverse electromagnetic wave in a hypothetical medium having a low crystalline symmetry and double anisotropy are formulated phenomenological based on the general concepts of Maxwell's equations. Formalism for electrical and magnetic ordering of a medium is represented by tensor coefficients of the second rank in a general coordinate system corresponding to an external problem of incidence, reflection and refraction of a transverse wave at the interface. Based on the obtained dispersion law, the Snell law of refraction for the wave vector is displayed, as well as, some special cases for a section of a wave surface and a ray surface in the plane of incidence. Following Fresnel approach as usual, two characteristic types of linear polarization of an electric induction vector of a propagating wave are considered for a wave entering a double anisotropic medium at an arbitrary angle to the interface. Based on a character of a cross-section of a wave surface and of a ray surface for the plane of incidence, the degree of influence of anisotropy on a propagating field is discussed in terms of external/internal conic refraction of ordinary/extraordinary waves in a transparent medium. Following to initially general form of the permittivity ε^ and the magnetic permeability μ^ tensors some particular cases of a more favorable choice of coordinate system are analyzed to decrease a number of non-zero components in mentioned tensors, as well as to decrease in the number of elements in vector relations.

Dielectric terahertz metasurface governed by symmetry-protected BIC for ultrasensitive sensing

The non-radiative bound states in the continuum (BIC) have attracted much attention in achieving theoretically infinite quality (Q) factor. In this paper, a dielectric terahertz metasurface with C 4v symmetry is proposed, and a toroidal dipole resonance is easily obtained under incident plane wave. Moreover, by slightly tuning the asymmetry parameter δ to break the in-plane symmetry of the structure (side length perturbation), a magnetic dipole BIC mode radiates as quasi-BIC (QBIC) with extremely narrow linewidth and ultrahigh Q of 1.2 × 104 at δ = 0.4 μm. It shows significant performance in THz sensing with the sensitivity around 446 GHz/RIU and figure of merit (FoM) up to 2267. The designed metasurface in the case of symmetry-breaking by position perturbation also achieves ultrasensitive sensing. Additionally, the effects of geometric parameters on the resonance modes have been comprehensively investigated. Our work provides a route to design symmetry-protected BIC metasurface with simple structure, and the Q factor as well as resonant frequency can be controlled using a single geometric parameter, which may facilitate designing high-performance metasurface in sensing applications.