Electromagnetic Waves Research Articles

Assorted optical solitons of the (1+1)- and (2+1)-dimensional Chiral nonlinear Schrödinger equations using modified extended tanh-function technique

In this research article, the (1+1)- and (2+1)-dimensional Chiral nonlinear Schrödinger equations (CNLSEs) are studied, which play an important role in the development of quantum mechanics, particularly in the field of quantum Hall effect. Our primary goal is to obtain the analytical solutions utilizing novel methodology, particularly the modified extended tanh-function technique. We concentrate on the search to solitary wave solutions inside the (1+1)- and (2+1)-dimensional CNLSEs, which are relevant in domains such as optics, electro-magnetic wave propagation, plasma physics, optics and quantum mechanics. Our objective is to increase knowledge of this equation and give insight into the behavior of solitary waves by employing a novel mathematical technique. This will be accomplished by displaying our findings in 2D and 3D graphics. We believe that our results would pave a way for future research generating optical memories based on the nonlinear solitons.

The frequency spectrum and energy content in a pulse flux of terahertz radiation generated by a relativistic electron beam in a plasma column with different density distributions

This paper reports on the generation of a directed flux of electromagnetic radiation with an energy content of 10 J in the frequency range of 0.2—0.3 THz at a microsecond pulse duration in a beam-plasma system. The flux is generated when a relativistic electron beam (REB) pumps electron plasma waves in a magnetized plasma column. In the described experiments, this fundamentally new approach to generate terahertz radiation was carried out at the GOL-PET facility in the conditions of varying the beam current density and the plasma density in the appropriate ranges of 1—2 kA/cm2 and 1014—1015 cm−3. From the comparison of the flux energy spectrum measured experimentally in the frequency range 0.15—0.45 THz with the calculated one obtained using the previously proposed model of radiation generation in a beam–plasma system, it was shown that this process occurs through resonant pumping by REB of precisely the branch of upper-hybrid plasma waves. Mastering this new method to generate terahertz radiation opens the prospect of its use to obtain multi-megawatt radiation fluxes in the frequency range up to 1 terahertz and higher. For such a development approach the most promising beam for pumping plasma oscillations seems to be a kiloampere REB generated in a linear induction accelerator.

Far-infrared irradiation inhibits proliferation of human upper airway epithelial cells via protein phosphatase 2A-promoted dephosphorylation of p70 S6 kinase.

Far-infrared (FIR) ray, an invisible electromagnetic radiation with a wavelength of 3‒1000μm, elicits various biological effects. Excessive proliferation of human upper airway epithelial cells (HUAEpCs) contributes to the development and exacerbation of nasal narrowing diseases, including nasal polyposis and chronic rhinosinusitis with nasal polyps (CRSwNP). Here, we investigated the molecular mechanisms through which FIR irradiation inhibits the proliferation of HUAEpCs. FIR irradiation significantly inhibited the proliferation of NCI-H292 cells without alteration in cell viability. The anti-proliferative effect of FIR radiation was accompanied by decreased phosphorylation of p70S6K at Thr389 (p-p70S6K-Thr389), without changes in the phosphorylation of mammalian target of rapamycin and adenosine monophosphate-activated protein kinase (AMPK). Overexpression of p70S6K-T389E mutant gene, not dominant negative-AMPKα1 gene, significantly reversed FIR irradiation-inhibited p-p70S6K-Thr389 and cell proliferation. Cotreatment with okadaic acid or knockdown of protein phosphatase 2A catalytic subunit (PP2Ac) gene expression significantly reversed FIR irradiation-decreased p-p70S6K-Thr389 and cell proliferation. FIR irradiation remarkably promoted the physical association of p70S6K and PP2Ac without change in total PP2Ac expression. Hyperthermal stimulus (39°C) did not alter p-p70S6K-Thr389 and cell proliferation. In line with NCI-H292 cell results, FIR irradiation, not hyperthermal stimulus, significantly decreased p-p70S6K-Thr389 and cell proliferation in primary human nasal turbinate and polyp epithelial cells. These results demonstrated that FIR irradiation decreased the proliferation of HUAEpCs through PP2A-mediated inhibition of p70S6K phosphorylation, independent of its hyperthermal effect. Our data suggest that FIR therapy can be used to treat upper airway narrowing epithelial hyperplastic diseases, including nasal polyposis and CRSwNP.

Effect of ultrahigh frequency ozone therapy on oxidative metabolism in the blood of rats with ischemic skin flaps: A preclinical experimental randomized study

Background. Maintaining and restoring skin microcirculation in surgical flaps, as well as accelerating rehabilitation after skin flap transplantation, in order to mitigate the consequences of burns and injuries, remain a pressing issue. In addition to various timings and techniques for plastic surgery, physiotherapeutic approaches prove to be efficient and include low-intensity electromagnetic radiation in millimeter waves as their prominent techniques. In recent years, experts have paid an increasing attention to the application of low-intensity electromagnetic radiation across different frequency ranges for the enhancement of microcirculation in patients after surgical correction of burn consequences. However, this approach is yet to be further validated. Objective. To investigate the effect of different combinations of ultrahigh frequency electromagnetic radiation with ozone therapy on the oxidative metabolism of blood in rats using a model of ischemic skin flaps. Methods. A preclinical experimental randomized study was conducted on 100 adult male Wistar rats weighing between 200 and 250 grams. Five equal-sized groups of animals were formed in the study: Group 1: intact (no interventions), and Groups 2, 3, 4, and 5: after surgical intervention (modeling of ischemic skin flaps). Animals in Group 2 (control group) received no therapeutic procedures. Rats in Groups 3 and 5 underwent a 10-minute course of electromagnetic radiation exposure with a dose of 0.06 mJ for seven days. Animals in Group 3 were exposed to electromagnetic radiation of ultrahigh frequency with a range of 53–78 GHz. Animals in Group 4 received injections of ozonized saline solution (with a saturating ozone concentration in the ozonized oxygen mixture of 3000 µg/L) daily for 7 days, administered intraperitoneally at a volume of 1 mL. Group 5 underwent a combined treatment: daily exposure to ultrahigh frequency electromagnetic radiation along with intraperitoneal ozone therapy (the application modalities of these treatments were similar to those used in Groups 3 and 4, respectively). The intensity of lipid peroxidation, peroxide resistance in erythrocytes, and overall antioxidant system activity were assessed in order to investigate the balance of pro- and antioxidant systems in plasma and erythrocytes. Additionally, the study involved determination of the level of malondialdehyde content and evaluation of the activity of superoxide dismutase and catalase in erythrocytes. The obtained date were analyzed, using MS Office 2013 (Microsoft Corporation, USA) and Statistica 10 (StatSoft, USA). Results. The conducted analysis revealed an antioxidant effect from ultrahigh frequency electromagnetic radiation, with this effect being enhanced by ozone therapy. In addition, the study detected the inhibition of free radical oxidation under the ultrahigh frequency electromagnetic radiation and ozone therapy. Conclusion. Thus, the positive effects of the studied therapeutic factors manifest at the systemic level, as evidenced by the optimization of biochemical parameters and indicators of oxidative metabolism in the plasma of animal blood. It has been established that ultrahigh frequency electromagnetic radiation, administered in a noise mode, exerts a regulatory effect on pro- and antioxidant systems in the body, as demonstrated in a model of transplanted skin flap. This intervention leads to a reduction in the severity of oxidative stress and an enhancement of antioxidant reserves in the blood. The observed effect is further amplified with the additional application of ozone therapy.

MoS2 Decorated on 1D MoS2@Co/NC@CF Hierarchical Fibrous Membranes for Enhanced Microwave Absorption.

The design and development of high-quality electromagnetic waves (EMW) absorbing materials play a vital role in combating the escalating negative effects of microwave radiation and interference. Herein, MoS2@Co/NC@CF fibrous membranes are successfully fabricated by electrospinning technology and carbonization, and a molybdenum disulfide (MoS2) layer is synthesized on the surface of these fibers via hydrothermal method. The seed-assisted growth method not only effectively avoids the accumulation and improves the loading of ZIF-67 particles, so as to ensure that the magnetic components in the fibers are evenly distributed in a wider range, rather than only intermittently present in some sites. Meanwhile, the introduction of semiconductor MoS2 as the shell further optimizes the impedance matching and improves the EMW absorption performance of the carbon fibrous membranes: the minimum reflection loss (RLmin) is -67.56dB, and the maximum effective absorption bandwidth (EABmax) is further expanded to 6.56GHz (2.1mm, 11.44-18GHz). This work provides a feasible method for developing high-efficient EMW-absorbing materials.

The glow of axion quark nugget dark matter

Context. The existence of axion quark nuggets is a potential consequence of the axion field, which provides a possible solution to the charge-conjugation parity violation in quantum chromodynamics. In addition to explaining the cosmological discrepancy of matter-antimatter asymmetry and a visible-to-dark-matter ratio of Ωdark/Ωvisible ≃ 5, these composite compact objects are expected to represent a potentially ubiquitous electromagnetic background radiation by interacting with ordinary baryonic matter. We conducted an in-depth analysis of axion quark nugget-baryonic matter interactions in the environment of the intracluster medium in the constrained cosmological Simulation of the LOcal Web (SLOW). Aims. Here, we aim to provide upper limit predictions on electromagnetic counterparts of axion quark nuggets in the environment of galaxy clusters by inferring their thermal and non-thermal emission spectrum originating from axion quark nugget-cluster gas interactions. Methods. We analyzed the emission of axion quark nuggets in a large sample of 161 simulated galaxy clusters using the SLOW simulation. These clusters are divided into a sub-sample of 150 galaxy clusters, ordered in five mass bins ranging from 0.8 to 31.7 × 1014 M⊙, along with 11 cross-identified galaxy clusters from observations. We investigated dark matter-baryonic matter interactions in galaxy clusters in their present stage at the redshift of z = 0 by assuming all dark matter consists of axion quark nuggets. The resulting electromagnetic signatures were compared to thermal Bremsstrahlung and non-thermal cosmic ray (CR) synchrotron emission in each galaxy cluster. We further investigated individual frequency bands imitating the observable range of the WMAP, Planck, Euclid, and XRISM telescopes for the most promising cross-identified galaxy clusters hosting detectable signatures of axion quark nugget emission. Results. We observed a positive excess in the low- and high-energy frequency windows, where thermal and non-thermal axion quark nugget emission can significantly contribute to (or even outshine) the emission of the intracluster medium (ICM) in frequencies up to νT ≲ 3842.19 GHz and νT ϵ [3.97, 10.99] × 1010GHz, respectively. Emission signatures of axion quark nuggets are found to be observable if CR synchrotron emission of individual clusters is sufficiently low. The degeneracy in the parameters contributing to an emission excess makes it challenging to offer predictions with respect to pinpointing specific regions of a positive axion quark nugget excess; however, a general increase in the total galaxy cluster emission is expected based on this dark matter model. Axion quark nuggets constitute an increment of 4.80% of the total galaxy cluster emission in the low-energy regime of νT ≲ 3842.19 GHz for a selection of cross-identified galaxy clusters. We propose that the Fornax and Virgo clusters represent the most promising candidates in the search for axion quark nugget emission signatures. Conclusions. The results from our simulations point towards the possibility of detecting an axion quark nugget excess in galaxy clusters in observations if their signatures can be sufficiently disentangled from the ICM radiation. While this model proposes a promising explanation for the composition of dark matter, with the potential to have this outcome verified by observations, we propose further changes that are aimed at refining our methods. Our ultimate goal is to identify the extracted electromagnetic counterparts of axion quark nuggets with even greater precision in the near future.

Multifunctional ANF/ CNT/FCIP aerogels with superior sound and electromagnetic wave absorption and mechanical properties

Aerogels exhibit bright prospect for multifunctional applications in noise reduction, radar stealth, load bearing, etc. Existing aerogels however suffer from poor sound absorption at low frequencies, narrow-band electromagnetic wave absorption and low structural strength. Here, we propose a novel lightweight aerogel composed of aromatic polyamide nanofiber (ANF)/ carbon nanotubes (CNT)/ flake carbonyl iron powder (FCIP) to boost acoustic/electromagnetic absorption and mechanical performance simultaneously. The FCIP additives create surface roughness and enlarge the pore size of the aerogel. As a result of the enhanced viscous energy dissipation by surface roughness and better impedance match achieved due to the enlarged pores, sound absorption at low frequency is significantly improved. Besides, the electrically and magnetically conductive network generated by embedded FCIP brings about effective electromagnetic absorption covering the whole X-band. Moreover, the aerogels undergo an increase in skeleton thickness and pore size by FCIP, resulting in maximum compressive stress increment. Our study provides clear guidance for the performance enhancement of aerogels that advances the development of aerogels for multifunctional applications.

Ionospheric Absorption Variation Based on Ionosonde and Riometer Data and the NOAA D-RAP Model over Europe During Intense Solar Flares in September 2017

A novel method was developed based on the amplitude data of the EM waves measured by Digisondes to calculate and investigate the relative ionospheric absorption changes. The effect of 13 solar flares (>C8) that occurred from 4 to 10 September 2017 were studied at three European Digisonde stations (Juliusruh (54.63°N, 13.37°E), Průhonice (49.98°N, 14.55°E) and San Vito (40.6°N, 17.8°E)). The present study compares the results of the amplitude method with the absorption changes measured by the Finnish Riometer Network and determined by the NOAA D-RAP model during the same events. The X-class flares caused 1.5–2.5 dB of attenuation at 30–32.5 MHz based on the riometer data, while the absorption changes were between 10 and 15 dB in the 2.5–4.5 MHz frequency range according to the amplitude data. The impact caused by energetic particles after the solar flares are clearly seen in the riometer data, while among the Digisonde stations it can be observed only at Juliusruh in some certain cases. Comparing the results of the amplitude method with the D-RAP model it seems evident that the observed absorption values almost always exceed the values given by the model both at 2.5 MHz and at 4 MHz during the investigated period. According to the comparison between the riometer data with the D-RAP, generally, the model underestimates the absorption values obtained from the riometers during solar flares except at the highest latitude stations, while D-RAP overestimates the impact during the particle events.

A Closer Look at Dwarf Galaxies Exhibiting Mid-infrared Variability: Active Galactic Nuclei Confirmation and Comparison With Nonvariable Dwarf Galaxies

Detecting active black holes in dwarf galaxies has proven to be a challenge due to their small size and weak electromagnetic signatures. Mid-infrared variability has emerged as a promising tool that can be used to detect active low-mass black holes in dwarf galaxies. We analyzed 10.4 yr of photometry from the AllWISE/NEOWISE multiepoch catalogs, identifying 25 objects with active galactic nuclei (AGN)-like variability. Independent confirmation of AGN activity was found in 68% of these objects using optical and near-infrared diagnostics. Notably, we discover a near-infrared coronal line [S ix] λ 1.252 μm in J1205, the galaxy with the lowest stellar mass (log M * = 7.5 M ⊙) and low metallicity (12 + log(O/H) = 7.46) in our sample. Additionally, we find broad Paα potentially from the broad-line region in two targets, and their implied black hole masses are consistent with black hole-stellar mass relations. Comparing nonvariable galaxies with similar stellar masses and Wide-field Infrared Survey Explorer W1 − W2 colors, we find no clear trends between variability and large-scale galaxy properties. However, we find that AGN activity likely causes redder W1 − W2 colors in variable targets, while for the nonvariable galaxies, the contribution stems from strong star formation activity. A high incidence of optical broad lines was also observed in variable targets. Our results suggest that mid-infrared variability is an effective method for detecting AGN activity in low-mass galaxies and can help uncover a larger sample of active low-mass (<106 M ⊙) black holes in the Universe.

Functionalized Nanodiamonds for Targeted Neuronal Electromagnetic Signal Detection.

Intracellular sensing technologies necessitate a delicate balance of spatial resolution, sensitivity, biocompatibility, and stability. While existing methods partially fulfill these criteria, none offer a comprehensive solution. Nanodiamonds (NDs) harboring nitrogen-vacancy (NV) centers have emerged as promising candidates due to their sensing capabilities under biological conditions and their ability to meet all aforementioned requirements. This study focuses on expanding the application of NDs and NV center-based sensing to neuronal contexts by investigating their functionalization and subsequent effects on three distinct cell lines relevant to neurodegenerative disease research. Our study concentrates on positioning fluorescent NDs (FNDs) with NV center point defects onto neuronal cell surfaces. Achieving this through specific antibody attachment enhances the proximity of FND to neurites, facilitating the detection of local action potentials. Targeting voltage-dependent calcium channels (Cav2.2) with biotin-streptavidin-bound antibodies enables the precise positioning of FNDs. The functionalized FNDs (f-FNDs) show increased size and zeta potential, confirming the antibody presence without compromising cell viability. Two-color confocal imaging and co-localization algorithms are employed to further attest to the success of the functionalization. The f-FNDs are applied to cell cultures of three cell lines: SH-SY5Y, differentiated dopaminergic neurons, and hippocampal rat neurons; their biocompatibility and effects on synaptic activity are explored. Moreover, preliminary total internal reflection fluorescence - optically detected magnetic resonance (TIRF-ODMR) experiments across cellular sites demonstrate the magnetic field sensitivity of our sensor network. The successful establishment of this sensor network provides a platform for characterizing neuronal signaling in healthy models and conditions mimicking Parkinson's disease.

A novel artificial intelligence‐based antenna designing model for optimizing 5G mobile communication

AbstractAntenna designing involves the creation of devices to transmit or receive electromagnetic signals for various applications. It encompasses optimizing parameters such as size, shape, and frequency response to achieve desired performance characteristics, including signal strength, bandwidth, and efficiency, across diverse communication systems and frequencies. In this research, we intend to establish a novel artificial intelligence (AI)‐based antenna designing model for optimizing 5th generation (5G) mobile communication. We proposed Multi‐Objective Zebra Optimization (MOZO) to enhance 5G antenna design, aiming to minimize return loss () and maximize gain (G) concurrently. MOZO efficiently explores design space, offering Pareto‐optimal solutions that balance objectives. This approach ensures optimal antenna performance across the desired frequency range, advancing 5G communication efficiency. Our model enhances the functionality of a small, rectangular patch antenna designed for the 5G band, specifically operating at 30 GHz. Additionally, we conducted a comparative analysis between the performance of our optimized rectangular 5G antenna and several recently employed 5G‐millimeter wave (mmWave) antennas. This comparison sheds light on the efficacy and competitiveness of our optimized design within the 5G‐mmWave antenna landscape.

Interlayer growth of magnetic nanocomponent in Ti3C2Tx MXene EMW absorbers for periodic electromagnetic synergetic network

Transition metal carbides/carbonitrides (MXene) exhibit huge potential as electromagnetic wave (EMW) absorbers in dealing with electromagnetic radiation problem that rise due to the rapid development of 5G era. The incorporation of magnetic materials can effectively mitigate the impedance mismatch and singular loss mechanisms inherent in pure MXenes (PMs). However, challenges persist due to issues such as random distribution, complex preparation processes, and inadequate interaction. In this study, Ti3C2Tx/Ni hybrids were synthesized using a one-pot method, wherein Ni, derived from molten salt, replaces Al layer of MXene, facilitating the in-situ growth of Ni nanocomponents within the interlayered region. The periodic electromagnetic synergetic network of “MXene-Ni-MXene-Ni-MXene” provides substantial magnetic resonance, eddy current loss, interface polarization, defect polarization, and dipole polarization, enriching the loss mechanism. By regulating the concentration of Ni, the intrinsic poor impedance matching of MXene was improved. Consequently, Ti3C2Tx/Ni hybrid exhibited exceptional electromagnetic wave absorption (EMA) performance, achieving a reflection loss (RL) of −64.51 dB and an effective absorption bandwidth (EAB) of 4.96 GHz at a matching thickness of 1.98 mm. Additionally, the super radar cross-section (RCS value = −15.73 dB m2) endow it potential in practical application. This work provides a facile method for achieving unique electromagnetic synergetic loss mechanism, thus paving the way for exploring high-efficient MXene-based EMW absorbers.

Influence of carbon nanotubes on the absorption performance and mechanical behavior of basalt fiber composite materials

AbstractBasalt fibers (BF) are widely used in shipbuilding due to their excellent corrosion resistance. However, basalt fibers do not possess good electromagnetic wave absorption properties, failing to meet the stealth performance requirements of ships. Therefore, this study focuses on basalt fiber composite materials, modifying the matrix by adding different amounts of carbon nanotubes (CNTs). Carbon nanotube‐basalt fiber‐epoxy resin absorptive composite materials are prepared using Vacuum Assisted Resin Transfer Molding (VARTM) technique to investigate the influence of CNT content on the materials. Samples with added CNTs can effectively absorb electromagnetic waves in the low‐frequency range, reducing surface reflectivity. In the high‐frequency range, the impedance matching value of the samples initially increases slowly. When the CNT content reaches 1.5 wt%, at a thickness of 2.5 mm and a frequency of 9.6 GHz, the minimum reflection loss of the sample is −14.40 dB, with an effective absorption bandwidth of 0.7 GHz. Also, CNTs can enhance the mechanical properties of composite materials. With increasing CNT content, both the bending strength and tensile strength of the composite materials are improved. When the CNT content reaches 1.5 wt%, the average tensile fracture strength of the material increases by 21%, and the bending strength increases by 9%.Highlights Enhanced low‐frequency electromagnetic wave absorption from CNTs and reduced polarization. Improved impedance matching and attenuation at high frequencies with CNTs. Significant enhancement in flexural and tensile strength due to CNTs and basalt fibers.

Effects of radiofrequency electromagnetic radiation with a focus on haematology parameters

The use of radiofrequency electromagnetic radiation (RF-EMR) has steadily increased since the 1950s. RF-EMR is used in medicine, industry, household appliances, security and navigation, and especially in wireless elecommunications and animal husbandry. The widespread use of RF-EMR, especially with the introduction of 5G networks, raises concerns about potential adverse effects on human and animal health. The effects and mechanisms of RF-EMR impacts of 5G network frequencies on human and animal health are still unknown orpoorly understood. Current research findings include the biological effects of RF-EMR on genotoxicity, cell proliferation, gene expression, cell signalling, cell membrane function, and the function of immune, ematopoietic, and reproductive systems. Exposure of humans and laboratory animals to RF-EMR emitted from cell phones and many other electronic devices of 4G and older technologies has been shown to have detrimental effects on blood cells and to cause changes in the complete blood count. This depends on the type of organisms exposed, sources,frequency, electric field level and duration of exposure. There is sparse data in the available literature on the effects of RF-EMR on haematology indicators and erythrocyte morphometry in domestic animals. Therefore, the aim of this scientific review is to highlight the effects of RF-EMR on haematology indicators, erythrocyte morphometry, and platelet activation in humans and animals, taking into account the findings on the effects of 5G electromagnetic radiation on these indicators. Considering the ubiquitous electromagnetic pollution, it is important to gain knowledge about the effects of RF-EMR on human and animal health. In addition, it is necessary to determine the effects following in vitro exposure of blood to RF-EMR, especially due to the storage and use of blood and blood products in transfusion medicine.

High‐efficiency electromagnetic absorption of HfC–SiCf ceramics with a 3D reticular structure

AbstractThe development of high‐temperature electromagnetic (EM) wave absorbing materials is an important direction for achieving radar stealth in high‐speed aircraft. In this study, HfC–SiCf composite ceramics with 3D reticular structure were synthesized in one‐step using the molten‐salt‐assisted carbon thermal reduction method. During the synthesis process, SiC grew in situ into a fibrous structure with a diameter of 500 nm and lengths ranging from 2 to 30 µm. By adjusting the molar ratio of HfC to SiC, the HfC‐30 mol% SiC (HS30) exhibited the best EM absorption performance at room temperature, with a minimum reflection loss (RLmin) of −31.4 dB at 16.1 GHz and an effective absorption bandwidth (EAB) of 4.6 GHz. The excellent absorption performance was attributed to the 3D reticular structure composed of SiC fibers, HfC bulk, and HfC nanoparticles, which significantly increased the number of pores and heterogeneous interfaces in the material. These microinterfaces induced interface polarization effects, thereby effectively enhancing the EM absorption. As the temperature increased, the EM absorption performance declined. At 900°C, the HS30 sample exhibited an EAB of 1.18 GHz from 12.4 to 13.58 GHz and an RLmin of 22.6 dB at 13.0 GHz. This research provides references for understanding the effects of material composition and structure on EM absorption performance.

Full-space trifunctional metasurface with independent control of amplitude and phase for circularly polarized waves

Abstract Flexible and diverse manipulation of electromagnetic (EM) waves in half space (reflection or transmission) has facilitated strong aspiration toward full-space wave control. However, it remains challenging to achieve independent amplitude and phase control, which seriously hinder the real-world applications. Herein, an innovative strategy of trifunctional metasurface is proposed to independently and simultaneously manipulate the amplitude and phase of circular polarized waves in full space. The multifunctional design is composed of double-layer anisotropic metasurface sandwiched with a bandpass frequency selective surface, with a frequency-direction multiplexed paradigm for on-demand control of both amplitude and phase across three independent channels. To validate the concept, a multifunctional metadevice is designed and verified by simulations and experiments, showcasing arbitrary near-field and far-field power modulation in full space. Lateral and axial bifocal metalenses with desired intensity distribution are designed in two reflection channels at 9 GHz, while multibeam generator with desired spatial scatterings and power allocations is designed in transmissive channel at 13 GHz. The finding paves the way for attaining multifunctional metadevices with amplitude and phase modulation in full space, which have potential applications in high-quality imaging and high-capacity communication systems.

Metasurface with high cross-polarization isolation using rectangular split rings for simultaneous amplitude and phase controls

Metasurfaces have demonstrated significant potential for versatile modulation of electromagnetic waves. To enhance the control of electromagnetic waves, simultaneous control of amplitudes and phases is often essential in certain applications. The C-shaped split ring (SR) with polarization conversion and its deformed structures can fulfill this requirement; however, such structures encounter the challenge of low polarization isolation, which is mainly reflected in its inherent characteristics of low polarization isolation and the deterioration of polarization isolation in amplitude control. In this paper, a reflective metasurface with improved polarization isolation is proposed. The designed metasurface consists of rectangular split ring (R-SR) elements, which can realize both amplitude and phase controls simultaneously and independently while exhibiting higher polarization isolation than the conventional SR element. Furthermore, an alternating mirror rotation method (AMRM) for the arrangement of amplitude-control elements is proposed to suppress the degradation of polarization isolation caused by amplitude control. Several metasurfaces are designed to verify the characteristics of the proposed R-SR structure and the effectiveness of the AMRM. Finally, two reflective metasurfaces composed of R-SR elements and SR elements with identical configurations are designed and manufactured. Both the simulation and measured results demonstrate the versatility of the proposed design and its advantages in terms of polarization isolation and transfer efficiency.

Ultralight Cellulose-Derived Carbon Nanofibers from Freeze-Drying Emulsion Towards Superior Microwave Absorption

Carbon nanofibers (CNFs) are usually prepared by the carbonization of cellulose aerogels obtained from freeze-drying. However, cellulose with low concentration (below 1 wt%) is required to maintain the good porosity of the aerogels due to the strong hydrogen bonding between the cellulose molecules. In order to address this problem, here, ultralight cellulose-derived CNFs have been fabricated by freeze-drying cyclohexane (CHE)/cellulose nanofiber emulsions and carbonization. Field emission scanning electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy are used to characterize the resulting CNFs. It is found that the CNFs consist of three-dimensional carbon networks, whose microstructure is easily adjusted by changing the CHE ratio (from 0 to 25 vol%) in the emulsions. The CNFs with high porosity are attributed to the fact that CHE as the oil phase can effectively weaken the hydrogen bonding and reduce the aggregation of the cellulose nanofibers. Carbon lattice defects and residual oxygen-containing functional groups are regarded as polarization centers, leading to the enhancement of dielectric loss. The conductive carbon networks also improve the conductive loss. All these factors improve the microwave absorption performance of the CNFs. So, the produced CNFs exhibit a superior electromagnetic wave performance with a minimum reflection loss of −42.18 dB and effective absorption bandwidth up to 4.9 GHz at 2 mm with a filling ratio of 2 wt%. This work provides a simple, low-cost, and sustainable synthesis route for CNFs used for ultralight high-performance microwave absorption materials.

Self-Assembly Hybrid Manufacture of Nanoarrays for Metasurfaces.

The development of metasurfaces necessitates the rapid fabrication of nanoarrays on diverse substrates at large scales, the preparation of patterned nanoarrays on both planar and curved surfaces, and even the creation of nanoarrays on prefabricated structures to form multiscale metastructures. However, conventional fabrication methods fall short of these rigorous requirements. In this work, a novel self-assembly hybrid manufacturing (SAHM) method is introduced for the rapid and scalable fabrication of shape-controllable nanoarrays on various rigid and flexible substrates. This method can be easily integrated with other fabrication techniques, such as lithography and screen printing, to produce patterned nanoarrays on both planar and non-developable surfaces. Utilizing the SAHM method, nanoarrays are fabricated on prefabricated micropillars to create multiscale pillar-nanoarray metastructures. Measurements indicate that these multiscale metastructures can manipulate electromagnetic waves across a range of wavelengths. Therefore, the SAHM method demonstrates the potential of multiscale structures as a new paradigm for the design and fabrication of metasurfaces.

Energy in the heart of EM waves: modelling, measurements and management—Foreword

Energy in the heart of EM waves: modelling, measurements and management—Foreword