Surface Electric Field Distribution Research Articles

Design of 2.5-D Miniaturized Frequency Selective Surface with Enhanced Oblique Stability

Abstract This paper presents a miniaturized 2.5-D frequency selective surface (FSS) that exhibits a band stop response at frequency of 1.5 GHz. In the unit cell, the meander patterns on both sides of the substrate are connected in series by four vias. Moreover, the meandered pattern in each quadrant is also connected with one of the meander patterns of the adjacent unit cell. In this manner, a 2.5-D closed loop is created with large perimeter. The enlarged perimeter amplifies the effective inductance and leads to a decrease in both the resonant frequency and the dimensions of unit cell. Subsequently, the proposed FSS demonstrates excellent miniaturization with an overall size of 0.038 λ0 × 0.038 λ0. Moreover, the frequency response is highly stable up to 86° for both TE and TM polarization. The resonance mechanism of the designed FSS is explicated through distribution of surface current and electric field. The testing board of the proposed FSS has been fabricated for the verification of the design. The measured frequency response of the prototype are congruent with the simulation results. The distinguished features of the constructed structure are enhanced angular stability, miniaturized unit cell, low profile, simple geometry and easy fabrication.

A bifunctional metamaterial with broadband properties of absorption and linear-to-linear polarization conversion

This paper proposes, measures, and investigates a bifunctional metamaterial capable of achieving absorption and reflective linear-to-linear polarization conversion simultaneously, which both exhibit the characteristics of broadband. The unit cell consists of a metal pattern with resistors, a dielectric plate, an air layer, and a metal backplate. The simulation results demonstrate that the designed metamaterial acquires over 90% absorption in the microwave band of 6.5–9.3 GHz. Within the frequency range of 12.7 GHz–17.2 GHz, the polarization conversion rate exceeds 90%, effectively converting y-polarized incident waves into x-polarized reflected waves. The experimental results align with the simulation data. The surface current and electric field distributions are utilized to analyze the absorption and polarization conversion phenomena. This bifunctional metamaterial exhibits potential application in radar imaging, enhancing data transmission rates, and wireless communication.

SiC-on-insulator based lateral power device and it’ s analytical models

This paper proposes the concept of SiC-on-insulator (SiCOI) lateral power device and its analytical models. The SiCOI technology provides dielectric isolation and improves the vertical breakdown. The analytical models provide the physic insight of the surface potential and electric field distributions for both full and partial depletion cases. The optimal breakdown voltage and doping concentration are deduced to analyze the breakdown mechanism qualitatively. The specific on-resistance in the drift region was also calculated to analyze the conduction characteristics. The influences of the structure parameters on the performances of the SiCOI lateral power device are investigated by the analytical model and numerical simulation. The analytical results of the proposed model are well agreement with the numerical results, confirming the validity of the proposed unified analytical model. Both the analytical and numerical results provide the physical explanation and effective solution for optimizing the electric field and improving breakdown voltage for the SiCOI lateral power device.

In situ Implanting 3D Carbon Network Reinforced Zinc Composite by Powder Metallurgy for Highly Reversible Zn-based Battery Anodes.

Aqueous Zn-based batteries have emerged as compelling candidates for grid-scale energy storage, owing to their intrinsic safety, remarkable theoretical energy density and cost-effectiveness. Nonetheless, the dendrite formation, side reactions, and corrosion on anode have overshadowed their practical applications. Herein, we present an in situ grown carbon network reinforcing Zn matrix anode prepared by powder metallurgy. This carbon network provides an uninterrupted internal electron transport pathway and optimize the surface electric field distribution, thereby enabling highly reversible Zn deposition. Consequently, symmetrical cells demonstrate impressive stability, running for over 880 h with a low voltage hysteresis (≈32 mV). Furthermore, this Zn matrix composite anode exhibits enhanced performance in both the aqueous Zn-ion and the Zn-air batteries. Notably, Zn//MnO2 cells display superior rate capabilities, while Zn-air batteries deliver high power density and impressive Zn utilization rate (84.9 %). This work provides a new idea of powder metallurgy method for modified Zn anodes, showcasing potential for large-scale production.

In situ Implanting 3D Carbon Network Reinforced Zinc Composite by Powder Metallurgy for Highly Reversible Zn‐based Battery Anodes

AbstractAqueous Zn‐based batteries have emerged as compelling candidates for grid‐scale energy storage, owing to their intrinsic safety, remarkable theoretical energy density and cost‐effectiveness. Nonetheless, the dendrite formation, side reactions, and corrosion on anode have overshadowed their practical applications. Herein, we present an in situ grown carbon network reinforcing Zn matrix anode prepared by powder metallurgy. This carbon network provides an uninterrupted internal electron transport pathway and optimize the surface electric field distribution, thereby enabling highly reversible Zn deposition. Consequently, symmetrical cells demonstrate impressive stability, running for over 880 h with a low voltage hysteresis (≈32 mV). Furthermore, this Zn matrix composite anode exhibits enhanced performance in both the aqueous Zn‐ion and the Zn‐air batteries. Notably, Zn//MnO2 cells display superior rate capabilities, while Zn‐air batteries deliver high power density and impressive Zn utilization rate (84.9 %). This work provides a new idea of powder metallurgy method for modified Zn anodes, showcasing potential for large‐scale production.

Ni-PI-Ni based nanoarchitectonics near-perfect metamaterial absorber with incident angle stability for visible and near-infrared applications

This article presents a wideband metamaterial absorber (WMMA) for the visible and near-infrared (NIR) region application. The proposed metamaterial absorber comprises three layers of sandwiched (metal-dielectric-metal) model based on Nickel-Polyamide-Nickel. The multiple resonators on top layers achieve an average absorption of 98.16% over a range from 380 to 2300 nm with a compact unit cell size of 100 × 100 × 42 nm3. The designed WMMA shows 99% perfect absorption for a large bandwidth of 685 nm. Considering its wideband absorption, the physical absorption phenomenon was also explained in terms of the proposed WMMA's surface electric field, magnetic field, and current distribution. Also, the effects of materials and structural parameters on absorption performance with a FOM have been studied. The absorption performance is analysed with various polarization angles to demonstrate polarization insensitivity. The designed WMMA shows the absorption of >70% at large incident angles of 70°. The perceptible contribution of this WMMA is large unity absorption bandwidth at visible to NIR region with high incident angle stability, polarisation insensitivity, thermal robustness of the constituting metal and simple nanostructure geometry. Therefore, the proposed WMMA has good potential in sensors, thermal emitters, photodetectors, and absorber applications.

Hierarchical porous carbon fibers for broadband and tunable high-performance microwave absorption

Constructing multiple polarization losses and improving impedance matching in carbon materials is essential for improving electromagnetic wave absorption performance of carbon materials. Meanwhile, surface contamination of electromagnetic wave absorbers has a significant impact on their absorption performance. Herein, a pod-like macroporous carbon nanofibers with self-cleaning function are successfully prepared by Electrospinning-etching strategy. Through the adjustment of SiO2 and pore structure, conduction loss, dipole polarization loss, interface polarization loss, and impedance matching of carbon nanofibers are optimized simultaneously. The optimized a pod-like macroporous carbon nanofibers has strong absorption and wide effective absorption bandwidth. With a cavity content of 4 %, the minimum reflection loss at 2.29 mm is -49.36 dB, and the effective absorption bandwidth is 7.6 GHz and the matched thickness is 2.16 mm. This result indicates that cavity and pod-like structure can significantly improve dielectric properties and enhance interface polarization loss and conductivity loss. The simulation results verify that the pod structure has a greater impact on surface electric field distribution, which shows that interface polarization is caused by the cavity structure. In addition, the contact angle of absorber is 105 °, which proves its self-cleaning ability. This functional absorbing material has potential to meet future practical applications.

Ultrafast All-Optical Switching Modulation of Terahertz Polarization Conversion Metasurfaces Based on Silicon.

With the development of ultrafast optics, all-optical control of terahertz wave modulation based on semiconductors has become an important technology of terahertz wave regulation. In this article, an ultrawideband terahertz linear polarization converter consisting of a double-layered metasurface is first proposed. The polarization conversion ratio of the device is ∼ 100% at 0.2-2.2 THz, and the transmission of copolarization approaches zero in the full band, which demonstrates the ability of high-purity output with rotating input linear polarization of 90° over an ultrawideband. By analysis of the surface current and electric field distribution, the physical mechanism of polarization conversion is elucidated. In addition, the influence of important geometric parameters on the device is discussed and analyzed in detail, which provides theoretical support for the design of high-performance polarization converters. More importantly, by introducing semiconductor silicon to construct an actively controllable metasurface, we design all-optical polarization converters based on a meta-atomic molecularization metasurface and all-dielectric metasurface; the dynamically tunable ultrawideband linear polarization conversion is realized under optical pumping, which solves the inherent problem of the performance of the metasurface polarization converters. Numerical simulation shows that the switching response of the two types of actively controllable devices under optical pumping is about 700 and 1800 ps, respectively, and can manipulate polarized wave conversion ultrafast, which brings new opportunities for all-optical controlled ultrafast terahertz polarization converters. Our results provide a feasible scheme for the development of state-of-the-art active and controllable ultrafast terahertz metasurface polarization converters, which have great application potential in short-range wireless terahertz communication, ultrafast optical switches, the transient spectrum, and optical polarization control devices.

A high-quality broadband tunable terahertz metamaterial absorber based on graphene

We design a graphene-based broadband tunable terahertz metamaterial absorber (MMA). Its structure consists of a surface graphene pattern layer, a medium layer and an underlying metal film. CST simulation results show that the absorption bandwidth for more than 90% absorption rate reaches 2.12 THz, and the range is 3.2–5.32 THz. The absorption bandwidth for more than 99% absorption rate reaches 1.38 THz, and the range is 3.45–4.83 THz, which was not achieved by most of the previous MMA. Multiple reflection interference theory is used to confirm the simulation results. In order to explore the physical mechanism of wideband absorption, we study the surface electric field distribution of the structure. We also find that the absorber has polarization insensitivity and wide-angle incidence characteristics. The absorption frequency of the absorber can be adjusted by changing the chemical potential of graphene. Therefore, the absorber has potential applications in terahertz absorption, filtering and sensing.

Dielectric exposed on DC-pulsed helium plasma jet: Hollow distribution of the surface electric field

In this study, the electric field distribution on the dielectric surface exposed to helium atmospheric pressure plasma jets with varying operating parameters was investigated. The study considered the effect of applied voltage (7–10 kV), pulse width (0.9–150 μs), and rate (400–2000 sccm), with the investigation based on the Pockels effect. The results suggest that the surface electric field arises from the charge transfer by ionization waves and the expansion of surface discharges. The evolution of the electric field can be segmented into three phases: establishment, maintenance, and dissipation. The gas flow rate determines the mixing “boundary” between helium and air, and consequently affects the shape of the surface electric field distribution. At 400 sccm, the field structure exhibits a solid, elongated shape. At 800–1200 sccm, the field takes on a hollow-ring appearance, and at 1600–2000 sccm, it is presented as two channels. As the applied voltage increases, the surface discharge can be extended further, even surpassing the designated boundary. At 10 kV, the maximum surface electric field and total deposited charge are 5.9 kV/cm and 4.3 nC, respectively. At a fixed frequency of 5 kHz, changing the pulse width affects charging time. The maximum value of the surface electric field and the total deposited charge exhibits an initial increase followed by a decrease. Short pulses (0.9–2 μs) result in incomplete charge transfer, while long pulses (100–150 μs) form a “dark channel” of predominantly negative charge at falling edge of the pulse, which neutralizes the positive charge in the subsequent pulse. A pulse width of 20 μs allows complete charge transfer with less influence from the dark channel.

Investigation of electric field distribution on dielectric exposed to DC-pulsed He plasma jet with shielding gas

Atmospheric pressure plasma jets (APPJs) produce reactive species and electric fields for biomedical applications. Gas shields control plasma plume-surrounding gas interactions, regulating reactive species generation and electric field strength. However, the surface electric field distribution is still unclear and needs urgent attention. Here, the electric field distribution on the surface exposed to a helium APPJ with shielding gas is investigated using the Pockels technique. This study considers the influence of the type of shielding gas (ambient air, dry air, nitrogen, oxygen, nitrogen-oxygen mixture) and the flow rate (2000–6000 sccm). The results show that the surface electric field develops in three phases: establishment, maintenance, and dissipation. Both flow rate and oxygen content of the shielding gas significantly influence surface discharge behavior and the maximum electric field value. The analysis suggests that the establishment phase of the electric field results from charge transfer by ionization waves to the dielectric, while the maintenance of the electric field depends on pulse duration. During the dissipation phase, the positive surface charge attracts negatively charged species to the surface (electrons and negative ions), which causes charge neutralization at the surface. The oxygen content in the shielding gas impacts the electric field establishment phase, with a low oxygen content leading to lower photo-ionization rates and, consequently, surface discharges with branching. Shielding gas flow rates affect the amount of shielding gas mixed into the helium channel. Mixing less oxygen into the APPJ increases the electric field strength, as the ionization potential is lower than nitrogen. Excessive oxygen mixing traps more free electrons due to electronegativity, causing fewer ionized collisions and more negative ions in APPJ, ultimately lowering the electric field strength. This study shows that shielding gas type and flow rates can adjust surface charging, aiding in optimizing biomedical APPJ.

Collaborative Optimization of Conductivity and Permittivity on GIL Spacer Surface for Electric Field Regulation Under DC Superimposed Impulse Voltages

The gas-solid interface electric field distortion is an essential factor leading to surface insulation failure. This study proposes the conductivity and permittivity-graded coating layer (ε/γ-layer) method, aiming at regulating surface charge and electric field distribution on GIL spacers under DC/ DC superimposed impulse voltages. The iteration optimization algorithm is developed to obtain the optimal conductivity and permittivity distribution of the ε/γ-layer. The surface charge and electric field behavior on GIL spacers with the ε/γ-layer are investigated through the numerical simulation approach. The polarity of the accumulated surface charges reverses on both the convex and concave sides as the conductivity of the ε/γ-layer increases under DC voltages, indicating the dominant mechanism changing from the bulk conductivity model to the surface conductivity model. The electric field distribution is also improved with the ε/γ-layer at the optimal permittivity and conductivity distribution. Compared with the raw spacer, the maximum electric field strength with ε/γ-layer is reduced by about 31.97% under DC, 20.56% under DC superimposed positive impulse (DC+Po.Im), 42.68% under DC superimposed negative impulse (DC+Ne.Im) on the convex surface, about 64.22% under DC, 21.37% under DC+Po.Im, 36.46% under DC+Ne.Im on the concave surface, correspondingly. It is hoped that the results of this study could spark off novel ideas for the optimal design of DC GIL spacers.

Active Control and Sensing Application of Ultra-Narrowband Circular Dichroism in Multilayer Chiral Nanorod Arrays.

Narrowband circular dichroism (CD) has attracted wide attention for its high sensitivity in detecting chiral molecules and catalysis. However, designing a chiral metasurface with excellent sensing performance that can be dynamically tuned still poses challenges. This paper introduces lithium niobate, an electrically tunable material, and a distributed Bragg reflector into chiral nanorod structures to form multilayer chiral nanorod arrays (MCNAs). Simulation results show that MCNAs can generate four strong ultra-narrowband (UNB) CD signals in the visible light spectrum. The UNB CD signal intensity was up to 0.86, and the minimum full width at half-maximum (FWHM) was up to 0.21 nm. The surface electric field and current distribution of MCNAs indicate that the four UNB CD signals mainly originate from the x and y direction Tamm resonances in the chiral nanorod layer. The refractive index of lithium niobate can be tuned by changing the electric field, allowing the active tuning of UNB CD signals. In addition, the sensing performance of MCNAs in the SARS-CoV-2 solution was analyzed, and the figure of merit (FOM) can reach an astonishing 2092. These findings not only assist with the design of UNB chiral devices but also offer new possibilities for the environmental monitoring and ultrasensitive detection of chiral molecules.

Improved electrical resistivity-temperature characteristics of oriented hBN composites for inhibiting temperature-dependence DC surface breakdown

In this paper, oriented hBN composites with anisotropic thermal conductivity are employed to improve electrical resistivity-temperature characteristics, thus inhibiting the occurrence of DC surface flashover under the temperature gradient by directionally manipulating heat flow. The DC surface flashover performance, electrical resistivity, carrier mobility, and electric field distribution of composites depending on the hBN orientation are studied at different temperatures. When the angle between the hBN basal plane and the axis of the electrodes is 90°, the out-of-plane oriented hBN composite shows the best electrical resistivity-temperature characteristics than that of the polymer filled with ceramic particles of positive temperature coefficient, whose surface flashover voltage is 28% higher than that of the out-of-plane oriented hBN composite with the angle of 0° between the hBN basal plane and the axis of the electrodes under the high-voltage electrode heated at 160 °C. The least rise in carrier mobility and electric field intensity near the GND electrode is the main factor in inhibiting the occurrence of DC surface flashover of the oriented hBN composites at high temperatures. The work presented in this paper will notably influence future research directions and modification solutions for DC dielectric materials.

Multiband Metasurface‐Based Absorber for Applications in X, Ku, and K Bands

AbstractIn this paper, a slotted‐circle patch metasurface that can efficiently absorb electromagnetic (EM) waves in three different bands is proposed. Based on the fundamental resonance of a single circular patch, EM resonances are generated making slits in the circular patch leading to multi‐band operation. Simulation results show that the proposed structure can absorb signals in three different bands, namely at 8.10, 15.39, and 19.7 GHz with absorption peaks of 99.8%, 99.7%, and 99.8%, and absorption bandwidths of 132, 181, and 90 MHz, respectively. The absorption mechanism is discussed on the basis of the single‐layer effective medium model and the analysis of surface current and electric field distributions. Furthermore, the experimental results show good agreement with the numerical simulations, with an average absorption greater than 99%. The 2‐mm thick absorber is electrically thin, corresponding to ∼λ/18 at its lowest operating frequency. Compared to other published designs, the proposed absorber has a single resonator with simple geometry, but operates in multiband. Therefore, it can be used in many applications such as anechoic chambers, scattering control, photodetectors, microbolometers, and solar cells. The proposed metasurface absorber can be used for microwave energy harvesting as well as sensor and radar cross‐section reduction applications.

High-conductivity nickel shells encapsulated wood-derived porous carbon for improved electromagnetic interference shielding

Biomass-derived carbon materials, especially from wood, have attracted great interests in electromagnetic interference (EMI) shielding ascribed to their sustainability and unique porous structures. However, it still lacks an effective approach to optimize its shielding performance through the microstructure design. Here, core@shell structure nickel encapsulated wood-derived porous carbon (PC) is prepared to improve the EMI shielding performance of porous carbon, in which the high-conductivity nickel shells is obtained through a chemical plating approach. The shielding effectiveness (SE) can reach 83 dB at 9.5 GHz, which is much higher than other reported shielding materials. Experimental results coupled with numerical simulations indicate that the surface and interface electric field distributions could result in a rapid transportation of EM energy and thus enhance the EMI shielding performance. Moreover, the shielding thin films prepared by such microparticles could demonstrate a superior SE of 104.5 dB with a normalized SE of 139.4 dB/mm. Our study opens a new pathway for designing EMI shielding materials based on biomass-derived core@shell structural carbon materials.

Experimental and numerical investigation of surface streamers in a nanosecond pulsed packed bed reactor

Packed bed reactor (PBR) is the commonly used configuration in plasma catalysis, and its plasma characteristics have been extensively investigated. The filled catalysts in PBR make it challenging to carry out in-situ measurements of electric fields, and limited experimental data have been obtained. We investigated the surface streamer propagation and electric field distribution in a simplified PBR through simulations and experiments. The simplified PBR in the experiments is comprised of a blade-plate electrode structure filled with an Al2O3 column (ϵr = 9) in the discharge gap. An ICCD camera and an electric field diagnosis method called EFISH (electric field induced second harmonic generation) were employed, and a two-dimensional fluid model was established for the simulation. Four discharge types in the PBR were identified based on ICCD images and simulation results, including polar discharge at the contact areas, surface streamer along the dielectric column, expansion of surface discharge along the dielectric column, and surface ionization waves along the dielectric plate. Surface streamers with opposite propagation directions were found in the model, namely the forward streamer during the pulse rising time and the reverse streamer during the pulse falling time. Notably, the reverse streamer exhibits a significantly lower velocity compared to the forward streamer. Both experimental measurements and simulation were conducted to investigate the spatiotemporal electric field near the surface of the packing material. The results of both E exp and E sim showed peaks with opposite polarities, and exhibited similar trends. In the simulation, the forward streamer head showed a higher electric field compared to the reverse streamer head. Moreover, during the rest pulse time, the surface electric field was more intense at the contact areas than in other regions. The findings of this work provide valuable insights into the discharge mechanism and electric field on the catalytic material surface within the PBR.

Collective-Coupling Enhanced Ultrabroadband Linear Polarization Conversion on Zigzag-Split Metasurfaces

Polarization manipulation plays a pivotal role in integrated multifunctional devices. Various metasurface-based polarization converters successfully demonstrated high efficiency and broad bandwidth. However, new mechanisms to aggressively enhance performance are still in dire need. Herein, theoretical and experimental evidence corroborates an efficient ultra-wideband transmissive polarization converter based on a topological design method. The triple-layer meta-device consists of a layer of anisotropic zigzag-split resonator array amid two orthogonal wire-grating layers. By splitting double zigzag lines into compound 90°V-shaped resonators, the intra-unit cross-coupling extends to strong inter-unit cross-coupling, giving birth to the multi-resonances enhancement and significant bandwidth broadening. This polarization converter can efficiently convert linearly polarized incident waves into 90° cross-polarized transmitted waves, with a conversion efficiency above 80% over 3.98-22.71 GHz, reaching a fractional bandwidth of 140.4%. The proposed meta-device enables strong cross-coupling in mutual transition from intra-unit to inter-unit. From a physical viewpoint, the novel mechanism is elucidated by the surface current and electric field distributions upon constructive interferences stemming from V-shape-resonator combinations and the Fabry-Pérot-like cavity effect. With both spectrum and function extensions, the proposed polarization conversion strategy finds essential applications in polarization-related systematic scenarios, such as 6G communication, radar imaging, anti-interference, chiral sensing, etc.

Dual-mode bidirectional multifunctional chiral metamaterial based on self-complementary resonators

In this paper, we propose an intrinsic chiral metamaterial (ICM) consisting of two metal self-complementary resonators, dielectric layer, and an embedded continuous vanadium dioxide (VO2) layer, which can operate in reflection and transmission modes and tailor different polarization manipulations for circular and linear polarized waves in opposite incident directions. When VO2 is in metallic state, the ICM can achieve broadband and narrowband circular polarization conversions at 1.52–2.50 THz and 2.93 THz for opposite propagating directions, respectively; when VO2 is in an insulating state, it shows a strong asymmetric transmission (AT) effect at 2.43 and 3.19 THz for forward and backward linear polarized waves. In addition, the physical mechanisms of different polarization operations are explained by analyzing the surface current and electric field distributions, multiple interference model, and near-field distributions in detail, and the circuit models are introduced to verify the simulated results. Furthermore, we investigate the influence of structural parameters on performance. The proposed ICM has important implications for the development of polarization detectors, frequency selectors, etc.

An Advanced Ceramic Material for Internal Insulation Used in Gas-Insulated HVDC Apparatus

The traditional polymer insulating material has encountered a bottleneck in improving the surface insulation performance in gas-insulated high voltage direct current (HVDC) apparatus. In this article, an advanced ceramic insulating material is proposed, which has great potential to be utilized in HVDC apparatus. The short-time and long-time surface insulation properties of the ceramic material are researched and compared with those of epoxy composite widely used at present. The conductivity and temperature dependence of the ceramic material is significantly lower than the epoxy composite. The surface charge accumulation and trap evolution characteristics of the ceramic can improve the surface electric field distribution. The long-time test further verifies its reliability, where the failure probability of the ceramic is 74% lower than that of the traditional material. This work may provide a basis for the application of the ceramic material in gas-insulated HVDC apparatus and may be helpful in understanding the surface insulation failure mechanisms in electro-thermal conditions.