Transverse Magnetic Research Articles

Ultrawide-Angle Broadband Electromagnetic Window for Both TM- and TE-Polarizations by Synergy of Multimechanism Resonances

As protective apparatus, electromagnetic windows (EMWs) are usually realized utilizing dielectric materials with higher permittivity or larger thickness to perform good mechanical properties. However, due to impedance mismatch, higher insertion loss is inevitably created, especially at large incident angles. It is now still a great challenge to engineer EMWs with stable operating bands and a wide range of incident angles for both transverse electric (TE)-and transverse magnetic (TM)-polarizations. In this article, we propose a method to achieve such EMWs by the synergy of multimechanism resonances, which enables broadband transmissions of both TM-and TE-polarized waves in an ultrawide range of incident angles. Fano resonance is first introduced to expand the bandwidth for TE-polarization on the basis of thickness resonance. Drude resonances are then introduced to suppress adverse influences of the parasitic Lorentz resonance for TM-polarization, to maximize the shared transmission band for TM-and TE-polarizations. The ultrawide-angle broadband functionalities of this EMW are validated by experiments, which agree well with numerical simulations. This work provides an efficient route to realize practical high-performance EMWs, under sufficient consideration of available materials, structures, and fabrication techniques, which may find wide applications in radar, communication, and imaging systems.

Design of a single layer single band 5G FSS as shielding materials

This paper deals with a novel Frequency Selective Surface (FSS) Electromagnetic shield that operates in the low 5G vertical applications. This FSS is designed for the purpose of serving as an electromagnetic shield to eliminate EMI. The FSS designed operates at a frequency of 5GHz with a bandwidth of 1.45GHz providing a shielding of more than 40dB. The proposed FSS uses a polyester sheet as substrate and uses silver for the metallization of the FSS. Since the proposed FSS is symmetric, it behaves similarly when a Transverse Electric (TE) or a Transverse Magnetic (TM) wave is incident. The structure was designed and simulated using CST software. The results show that this FSS blocks electromagnetic radiation at lower frequencies as intended.

Analytical Calculation of Hybrid Excitation Transverse Flux Permanent Magnet Synchronous Linear Motor Based on Schwarz–Christoffel Mapping

An analytical calculation method of thrust and suspension force based on Schwarz–Christoffel (SC) mapping is presented for hybrid excitation transverse flux permanent magnet synchronous linear motor (HETFPMSLM) applied to a maglev train. The effectiveness of the analytical calculation is verified by three-dimensional finite element analysis. Firstly, the structure and principle of HETFPMSLM are analyzed, and its longitudinal two-dimensional SC mapping model is proposed. The magnetic field of HETFPMSLM is calculated by MATLAB’s SC Toolbox. Then the suspension force and thrust are calculated by the Maxwell stress tensor method, which is compared with the 3D finite element to verify the accuracy of the analytical calculation.

Design and Performance Analysis of Permanent Magnet Claw Pole Machine with Hybrid Cores

Permanent magnet claw pole machine (PMCPM) is a special kind of transverse flux permanent magnet machine. Compared with other electrical machines, it has the advantages of high torque density and high efficiency for high speed operation. However, because of its complex irregular structure, the manufacturing process using silicon sheets is complicated. Soft magnetic composite material (SMC) is manufactured by powder metallurgy technology, which can produce various shapes of stator core structures, so it is easier to produce various irregular shapes of the stator core. However, the raw SMC material is relatively expensive, and the mechanical strength of SMC is weak. In this paper, a PMCPM with hybrid cores is proposed. With the adoption of hybrid silicon sheet — SMC cores and amorphous alloy — SMC cores, the torque ability of PMCPM can be improved greatly and it can have higher efficiency for more wide operation frequency. Meanwhile, its mechanical strength has been improved and it can be designed for high torque direct drive applications as it is a modular machine. Furthermore, three methods are proposed to reduce the additional eddy current loss which resulted from the employment of hybrid cores in PMCPM.

Quantum-enhanced sensing on optical transitions through finite-range interactions.

The control over quantum states in atomic systems has led to the most precise optical atomic clocks so far1-3. Their sensitivity is bounded at present by the standard quantum limit, a fundamental floor set by quantum mechanics for uncorrelated particles, which can-nevertheless-be overcome when operated with entangled particles. Yet demonstrating a quantum advantage in real-world sensors is extremely challenging. Here we illustrate a pathway for harnessing large-scale entanglement in an optical transition using 1D chains of up to 51 ions with interactions that decay as a power-law function of the ion separation. We show that our sensor can emulate many features of the one-axis-twisting (OAT) model, an iconic, fully connected model known to generate scalable squeezing4 and Greenberger-Horne-Zeilinger-like states5-8. The collective nature of the state manifests itself in the preservation of the total transverse magnetization, the reduced growth of the structure factor, that is, spin-wave excitations (SWE), at finite momenta, the generation of spin squeezing comparable with OAT (a Wineland parameter9,10 of -3.9 ± 0.3 dB for only N = 12 ions) and the development of non-Gaussian states in the form of multi-headed cat states in the Q-distribution. We demonstrate the metrological utility of the states in a Ramsey-type interferometer, in which we reduce the measurement uncertainty by -3.2 ± 0.5 dB below the standard quantum limit for N = 51 ions.

2D patterned magnetic composite sheets for polarization-insensitive and wide-angle microwave attenuation

Magnetic composite sheets loaded with carbonyl iron powders (CIP) are widely used due to their high-efficiency microwave attenuation at very thin thickness because of their outstanding permeability and magnetic loss. However, their performance varies dramatically at various incident angles and polarization modes, namely transverse electric (TE) and transverse magnetic (TM) modes. In this study, it is demonstrated that two-dimensional (2D) patterning could offer an effective solution for achieving wide-angle performance in both TE and TM modes. Different shapes of the 2D patterns (circles, hexagons, and cross-holes) are investigated and their dimensions are optimized through full-wave simulation. The consistent results with the experiment reveal that these 2D patterns with optimized dimensions could improve TM mode performance significantly to above 20 dB attenuation for an oblique incident angle up to about 40°, thanks to the resulted field resonance revealed by simulation. Due to the improved TM mode performance, the patterned composite sheet could exhibit almost identical high-efficiency attenuation in both modes, becoming polarization-insensitive. The performance improvement also comes with a ∼16% reduction in weight. Given these merits and the ease of fabrication, the low-profile and robust 2D patterned magnetic composite sheets could attract great attenuation in practical applications for wide-angle and polarization-insensitive microwave attenuation.

Incorporating interface permeability into the diffusion MRI signal representation while using impermeable Laplace eigenfunctions

Objective. The complex-valued transverse magnetization due to diffusion-encoding magnetic field gradients acting on a permeable medium can be modeled by the Bloch–Torrey partial differential equation. The diffusion magnetic resonance imaging (MRI) signal has a representation in the basis of the Laplace eigenfunctions of the medium. However, in order to estimate the permeability coefficient from diffusion MRI data, it is desirable that the forward solution can be calculated efficiently for many values of permeability. Approach. In this paper we propose a new formulation of the permeable diffusion MRI signal representation in the basis of the Laplace eigenfunctions of the same medium where the interfaces are made impermeable. Main results. We proved the theoretical equivalence between our new formulation and the original formulation in the case that the full eigendecomposition is used. We validated our method numerically and showed promising numerical results when a partial eigendecomposition is used. Two diffusion MRI sequences were used to illustrate the numerical validity of our new method. Significance. Our approach means that the same basis (the impermeable set) can be used for all permeability values, which reduces the computational time significantly, enabling the study of the effects of the permeability coefficient on the diffusion MRI signal in the future.

A polarization-dependent near-infrared metamaterial absorber based on the hybrid halide perovskite in two orthogonal directions

A wide-angle and polarization-sensitive metamaterial absorber is highly desired for near-infrared optical applications, such as stealth coatings, photovoltaic materials, and detectors. Although current near-infrared metamaterial absorbers achieve high absorption rates, they are typically either polarization-independent or only sensitive to one direction. Herein, a (CH3NH3)PbBr3-based perfect absorber with high absorption in both orthogonal directions and polarization sensitivity has been designed. The maximum absorption in the transverse magnetic (TM)-polarized light exceeds 99.6% at 800–1000 nm. The maximum absorption in the transverse electric (TE)-polarized light exceeds 98.9% at 1500–1800 nm, and the peak absorption is more than 84.3% at 1800–2200 nm using finite-difference time-domain methods. By modifying various structural parameters, the absorption of the absorber could be separately shifted in a wide wavelength region. In addition, the designed absorber maintains good performance at large angles of incidence. This structure can be applied to other hybrid perovskite materials by simply changing the structural parameters. These results present a huge potential for applications based on metamaterial absorbers, such as infrared polarization imaging, selective spectral detection, near-infrared sensing, and polarization multiplexing.

CPW-fed dual-element metamaterial inspired multiband antenna using simple FSS for gain enhancement

This article presents a dual-element metamaterial-inspired co-planar waveguide (CPW) fed elliptical antenna using a simple compact frequency selective surface (FSS) for multiband wireless applications. The designed antenna is fabricated on a cheap FR-4 substrate (εr = 4.4) with 40 × 40×1.6 mm3 dimensions. Dual complementary split ring resonators (CSRRs) loaded in the CPW ground create multiband characteristics, which are analyzed using the quasi-static design equations and the ANSYS HFSS EM simulator. FSS has been proposed as a reflector for the antenna to increase its gain. The FSS unit cell's angular stability has been analyzed using transverse electric (TE) and transverse magnetic (TM) polarization, and it has been determined to be 60°. The FSS integrated antenna offers measured bandwidths of 2.67 – 3.38 GHz (23.66 %), 3.77 – 4.17 GHz (10.25%), 4.91 – 5.93 GHz (19.61 %), and 7.28 – 8.93 GHz (20.24 %). The FSS integrated antenna shows nearly omnidirectional radiation patterns in all resonating bands with the highest gain of 9.72 dBi and measured radiation efficiency greater than 91 % in all the bands. The reported 'antenna with FSS' is appropriate for multiband wireless technologies as it covers IEEE 802.16 WiMAX, n77 5G NR, 5G Wi-Fi, WLAN, ISM and satellite spectrums.

A functionality switchable meta-device: from perfect reflection to perfect absorption

Tunable meta-devices trigger immense interest in many applications like biosensing, thermal camouflage, radiative cooling, thermal emitting, infrared imaging, and energy harvesting. This paper presents a polarization-independent broadband tunable absorbing and reflecting meta-device using a phase change material Germanium-Antimony-Tellurium (GST). The proposed design manifests high absorptivity >80% over a broadband range of wavelength spanning the mid-IR regime. Furthermore, by changing the phase of GST material from crystalline to amorphous with the help of external stimuli, the absorbance of the device was reduced to almost zero in the range from 4 μm to 12 μm. To previse the angular constancy of the meta-absorber, the absorptivity was scrutinized under different incidence angles in both transverse magnetic (TM) and transverse electric (TE) polarizations which manifested the robustness of the proposed meta-absorber. As a result, the proposed absorber has tunable broadband absorbance and angular stability, which proclaim great potential in applications such as thermal camouflage, radiation detection, thermal emitter, and stealth technology, etc.

Programmable nanophotonic planar resonator filter-absorber based on phase-change InSbTe

Reconfigurable plasmonic-photonic electromagnetic devices have been incessantly investigated for their great ability to optically modulate through external stimuli to meet today's emerging needs, with chalcogenide phase-change materials being promising candidates due to their remarkably unique electrical and optics, enabling new perspectives in recent photonic applications. In this work, we propose a reconfigurable resonator using planar layers of stacked ultrathin films based on Metal-dielectric-PCM, which we designed and analyzed numerically by the Finite Element Method (FEM). The structure is based on thin films of Gold (Au), aluminum oxide (Al2O3), and PCM (In3SbTe2) used as substrate. The modulation between the PCM phases (amorphous and crystalline) allows the alternation from the filter to the absorber structure in the infrared (IR) spectrum (1000–2500 nm), with an efficiency greater than 70% in both cases. The influence of the thickness of the material is also analyzed to verify tolerances for manufacturing errors and dynamically control the efficiency of transmittance and absorptance peaks. The physical mechanisms of field coupling and transmitted/absorbed power density are investigated. We also analyzed the effects on polarization angles for Transversal Electric (TE) and Transversal Magnetic (TM) polarized waves for both cases.

Step and graded-index core-based polymer multimode interference splitters for photonic integrated circuits

This paper demonstrates step-index (SI) and graded-index (GI) core-based multimode interference (MMI) splitters realized with polymer materials for photonic integrated circuits (PICs). These SI and GI index-based MMI splitters guide the input light through the multimode waveguide following the self-imaging principles and demonstrate the multiple outputs with the same uniformity when the self-imaging length is obtained. We numerically design and develop (1 ×5) MMI splitters using the beam propagation method (BPM), and we use the RSoft CAD BeamPROP solver for the structural design and waveguide characterization. The structures of the SI and GI MMI splitters are optimized by investigating the structural parameters, particularly the width and length of the multimode waveguide and the core spacing between the output ports with the maximum uniform intensity at the self-imaging length. We also compare the structural design and optical properties of the SI and GI MMI waveguides. The excess losses of the SI MMI splitter are 1.09 and 1.12 dB for transverse electric (TE) and transverse magnetic (TM) modes, respectively, while for the GI MMI splitter, the losses are 0.57 dB and 0.56 dB for TE and TM modes, respectively at 1.55 µm. The power splitting efficiency for the SI MMI splitter is 77%, and for the GI MMI splitter, it is 88%. We also investigate the polarization dependence loss (PDL) for both MMI splitters, and the losses for the SI and GI MMI splitters are 0.024 dB and 0.004 dB, respectively.

Crustal resistivity structures beneath the western flank across the Central Main Ethiopian Rift: Its implications for partial melt and pathways

The Wonji Fault Belt (WFB) and the Silti Debre Zeit Fault Zone (SDFZ) are two linear belts in the Central Main Ethiopian Rift (CMER) where recent magmatic and tectonic activities have been concentrated. To examine deep resistivity patterns, magma storage, and its path beneath the Earth's crust across the CMER, the researchers used a two-dimensional (2D) inversion model of magnetotelluric data. The time series magnetotelluric data ranging from 0.003125 to 1450.0 s were collected during >24 h of installations at 21 sites, with an average station separation of 2.5 km along a profile perpendicular to the rift from the western margin of the rift (near Butajira) to AdamiTulu (near the rift axis). This work describes the use of phase tensor analysis to determine the dimensionality and geoelectrical strike direction, as well as the estimation of geoelectric strike parameters and the 2D inversion model of MT data. The results of dimensionality analysis of the majority of our MT data show a small beta value (|β|<30) at low periods (nearly below 10 s), which indicates 1D or 2D structures, while at long periods (almost above 10 s), the data show 3D structures with a large value of |β| >30. However, from the results of the dimensionality analysis of MT data, the 2D inversion model is suitable to image the resistivity of subsurface structures. The dominant geo-electrical strike is estimated to be N150E using a Z-invariant and phase tensor azimuth. The 2D inversion model was performed after the MT data were rotated to the proper geoelectric strike direction of N150E. The desired 2D inversion of the resistivity model was obtained for the MT profile using joint inversion of TE (transverse electric) and TM (transverse magnetic) mode data with an RMS misfit of 1.11. The results of the 2D inversion model reveal partial melt and upper crustal fracture zone (fault). They are attributed to a large mass of batholithic or magmatic intrusion found at a depth of 12–22 km that is characterised by a resistivity of <5 Ωm. The partial melt extends beneath stations B07 to B11 along SDFZ with a horizontal width of approximately 10 km. It could be related to the source of heat for the Ashute and Aluto geothermal fields.

Comparative Study of Polarization‐Dependent Conversion Efficiency of GaAs and Si Solar Cells at Oblique Incident Angles Using Surface DLAR Coating of MgF2/ZnSe

AbstractThe aim of this work is to minimize reflection losses in order to increase the efficiency of solar cells by using anti‐reflection coatings (ARCs). Despite extensive research on improving solar cell conversion efficiency at normal incidence, development at angle of incidence has received little attention. Thus, the reflectivity of single‐layer ARC (SLARC) MgF2 and ZnSe, double‐layer ARC (DLARC), MgF2/ZnSe on Si, and GaAs substrates at transverse electric (TE) and transverse magnetic (TM) modes of polarization in the visible and near‐IR regions for different angles of incidence is analyzed. The optical and electrical properties of Si and GaAs solar cells are analyzed by using the reflectance spectra of SLARC and DLARC at various angles of incidence for the TM and TE modes of polarization under the solar power spectrum (AM1.5). The achieved results due to the effect of DLARC are compared for Si and GaAs solar cells. From these analyses, it is concluded that MgF2/ZnSe is an appropriate DLARC for the range of wavelengths 400–800 nm at 10°–30° angles of incidence in TM mode for tuning the optical and electrical properties of Si and GaAs substrates for terrestrial applications.

Miniaturization of a Fully Metallic Bandpass Frequency Selective Surface for Millimeter-Wave Band Applications

This article presents a miniaturized all-metallic bandpass frequency selective surface (FSS) for millimeter-wave (mmWave) applications. The designed FSS is realized as a slot-type element that can be easily incorporated into all-metallic device architectures. The miniaturization is achieved by a convoluted or meander slot structure, i.e., a miniaturization technique borrowed from conventional substrate-based FSS design. It is demonstrated that the proposed FSS element provides a stable and wide bandpass performance from 24.9 to 31.4 GHz for both the transverse electric (TE) and the transverse magnetic (TM) polarizations at the broadside direction ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\theta = 0^{\circ }$</tex-math></inline-formula> ). Adequate performance is maintained at oblique incidence angles up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\theta = \pm \,45^{\circ }$</tex-math></inline-formula> . A 25 × 25-elements FSS array prototype has been manufactured using the cost-effective chemical etching technique and experimentally characterized utilizing a free-space measurement setup. The results demonstrate a remarkably good correlation between simulations and measurements. Hence, the proposed miniaturized FSS represents an excellent potential to realize an all-metallic FSS with low insertion loss, low profile, and wideband performance at low fabrication costs for mmWave applications.

Tunable terahertz metamaterial with multi-resonance characteristic for refractive index sensing application

A tunable terahertz (THz) metamaterial (TTM) composed of double connected semicircle-shaped rings and two segregated metallic bars is presented. Through the manipulation of the radius of connected semicircle-shaped rings (R), the transverse electric (TE)-polarization resonance is red-shifted from 1.225 to 0.669 THz. The first and second transverse magnetic (TM)-polarization resonances can be systematically red-shifted from 1.225 to 0.669 THz and from 1.787 to 1.162 THz, respectively. By increasing the R value from 15.0 to 27.5 µm, the tuning trend of the free spectral range is linear over the range of 0.50 THz. Moreover, the TTM device shows polarization-dependent characteristics, which can be modulated by manipulating the distance between the semicircular-shaped ring structure and the metallic bar. The electromagnetic responses of the TTM device can be effectively tuned, enabling the possibility to switch between single-resonance in the TE mode, and dual-, triple-, and quad-resonance in the TM mode. The experiment and simulation results are agreed well. The TTM device can be employed as a sensor for evaluating the change of surrounding refractive index. The sensitivities between resonances and refractive indices are linear in the TE and TM modes. Therefore, TTM devices can be used for single-, dual-, triple-, and quad-resonance switching, polarization switching, and high-efficiency environmental sensing applications.

Simulation of low loss metamaterial based hollow core fiber for guiding mid-infrared (MIR) light

There is a great deal of interest in mid-infrared (MIR) light in diverse fields including spectroscopy, biomedical-applications, medical surgery, and astronomy. Due to higher material absorption, MIR light transmission is generally more difficult than visible light or microwave radiation. Recently, hollow-core MIR fibers are one of the best possibilities among presented several innovations having low Transverse Magnetic (TM) mode losses, although they are many orders of magnitude than Transverse Electric (TE) modes. Studies also have found that metamaterial-based HCF offers excellent potential for transmitting MIR light because of its distinct and flexible optical properties. In this study, a metamaterial-based HCF with an optimized design that uses metal wires with subwavelength spacing embedded in dielectric host, and acts as an effective TM reflector is proposed. In the 3 to 12 μm wavelengths, the effects of the design parameters including shape, number, and spacing of metal wires, dielectric thickness, and the diameter of the core are extensively investigated using finite element method. It is observed that TM01 mode losses are the lowest and a noteworthy confinement loss of 4.69× 10−7 dB/m is found at 9.5 μm wavelength, with an average loss of 5.22× 10−5 dB/m found within the range 8–10 μm wavelength. As the wires are wrapped up in a dielectric, there is a preferred position of 4 μm from the core edge and a number of 40 metal wires that results in the least amount of losses. This analysis could help to design low-loss metamaterial based HCF for guiding MIR light.

Ultrathin Narrowband and Bidirectional Perfect Metasurface Absorber

The conventional design approaches for achieving perfect absorption of electromagnetic (EM) waves using metasurface absorbers (MSAs) are limited to absorbing waves in one direction while reflecting waves in the other. In this study, a novel ultrathin narrowband MSA with bidirectional perfect absorption properties has been proposed, based on a tri-layer metal square-circular-square patch (SCSP) structure. The simulation results demonstrate that the proposed MSA exhibits a remarkable absorbance of 98.1%, which is consistent with the experimental and theoretical calculations. The equivalent constitutive parameters that were retrieved, as well as the simulated surface current and the power loss density distributions, reveal that the perfect absorption of the designed MSA originates from the fundamental dipolar resonance. Furthermore, the proposed MSA demonstrates stable wide-angle absorption properties for both transverse electric (TE) and transverse magnetic (TM) waves under various oblique incidence angles. The absorption characteristics of the MSA can be fine-tuned by adjusting the structural parameters. Additionally, the proposed MSA boasts excellent ultrathin thickness, bidirectional, polarization-insensitive, and wide-angle properties, making it highly suitable for a range of potential applications such as imaging, detection, and sensing.

Polarization-insensitive metamaterial perfect absorber in near-infrared band based on trapezoidal silver array

In this article, we presented our proposal for a metamaterial perfect absorber (MPA) operating in the near-infrared band. Our MPA comprised a trapezoidal silver layer, a substrate layer, and an intermediate alumina layer. The transmission characteristics of MPA were analyzed by the three-dimensional (3D) finite difference time domain method. The simulation results were analyzed by equivalent circuit theory. The results show that the MPA achieved 100% absorption of transverse magnetic (TM) polarization and transverse electric (TE) polarization with resonance wavelength = 1492.5 nm. By varying the length of the bottom side of the trapezoid, the MPA’s resonance wavelength could be effectively tuned, and the absorption was maintained at above 99%. With the incidence angle of 0°–55°, the absorption remains above 90% at TE polarization and above 80% at 55°–70°. The absorption at the TM polarization remains above 99% when the incident angle is 0°–70°. A wide angle of incidence and good absorption were achieved. The sensitivity (S) and figure of merit were 228 nm/refractive index unit and 1378 RIU−1, respectively. The proposed absorber with excellent absorption in the range of infrared spectra has a promising application potential in fields such as energy harvesting and infrared sensors.

Graphene-based polarization insensitive ultrathin broadband terahertz absorber for material sensing applications

In this paper, a tunable broadband electromagnetic absorber for sensing applications at terahertz frequencies is proposed. The proposed design consists of a graphene based multiple slot loaded rectangular resonator, dielectric material and gold based metallic ground plane. The dimensions of proposed absorber’s unit cell are 10 μm × 10 μm. The proposed absorber has more than 90% absorption over a frequency spectrum of 4.86–18.33 THz (% fractional bandwidth > 116.22%). The proposed absorber is symmetric which makes the structure polarization insensitive. It has stable characteristics for incidence angle (θ) ≥ 40∘ for both Transverse-Electric (TE) and Transverse-Magnetic (TM) waves. The effects of different substrate materials, different analyte materials, variations in the graphene parameters and water level on the proposed absorber’s performance are also analyzed. This absorber can be used to detect different materials including water and thickness of water layer present on its top surface. The proposed graphene-based absorber dominates previously reported wideband THz absorbers in terms of relative bandwidth, more than 90% absorption peak values, oblique stability and overall volume.