Band Electromagnetic Wave Research Articles

Multifunctional Radiation Conditioning Emitter for Laser and Infrared with Adaptive Radiative Cooling.

With the development of technology, multifunctional multiband emitters have been paid much attention due to their wide range of applications, such as LIDAR detection, spectroscopic sensing, and infrared thermal management. However, the development of such emitters is impeded by incompatible structural requirements of different electromagnetic wavebands. Here, we demonstrate coupled modulation between near-infrared (NIR) laser-wavelength and long-wavelength-infrared by constructing a multifunctional emitter (MFE) with a structure of Al/HfO2/VO2, utilizing the phase transition of VO2. The MFE displays excellent thermal modulation capability within the 8-14 μm range, achieving a thermal insulation effect (ε8-14μm = 0.18) at low temperatures, and heat dissipation effect (ε8-14μm = 0.64) at high temperatures. The MFE's radiation power regulation capability is 145.06 W m-2 between a temperature of 0 to 60 °C. Moreover, the MFE possesses a large reflectivity modulation value of 0.78 at NIR laser-wavelength (1.06 μm) with a short phase transition time of 1003 ms under 3 W cm-2 laser irradiation. This study provides a guideline for the coordinated control of electromagnetic waves and intelligent collaborative thermal management through simple structural design, thus, having broad implications in energy saving and thermal information processing.

Square & H metasurfaces for SPR Increasing in long Wave-IR absorber

In the long-wave infrared (LWIR) spectrum, this paper suggests an electromagnetic (EM) waveband absorber design based on metamaterials. Germanium, gold, and magnesium oxide layers are arranged in a layered structure from top to bottom in the suggested model. Our proposed metamaterial structure’s upper surface is composed of metallic metasurfaces with H and square forms from various studies. The finite element method is used to evaluate the metamaterials’ electromagnetic properties in terms of absorbance and reflectance. It is observed that there is a particular size of the metamaterial at which extremely localized electromagnetic resonance occurs. Quantitative findings indicate that the suggested metamaterial design’s average absorption reaches 90 % in the 10 μm to 14 μm range across a wide variety of incidence angles (00 to 400 & 00 to 800) for both transverse electric (TE) and transverse magnetic (TM) polarization. It is evident from these data that the suggested model configuration has broad potential applications in manyoptoelectronic fields of study.

Research on ultrasonic-electromagnetic wave simultaneous sensing sensors

Ultrasonic and electromagnetic wave detection signals are effective characterization signals for state detection, such as medical imaging, ocean exploration, and industrial applications.In order to simplify the complexity of ultrasonic and electromagnetic wave signal detection, this paper proposes a sensor design idea with both ultrasonic and electromagnetic wave sensing functions, and develops an ultrasonic-electromagnetic wave simultaneous sensing sensor based on the application scenario of ultrasonic and electromagnetic wave signal sensing requirements of discharge insulation defects of power equipment.The simulation results show that the voltage standing wave ratio of the sensor designed in this paper is less than 3.3 in the electromagnetic wave band of 0.3 GHz ∼ 3.0 GHz. The average ultrasonic sensitivity in the range of 20 kHz ∼ 80 kHz is 48 dB ( Ref 1 V / ( m / s)), and the peak sensitivity is 62 dB.Finally, the construction of power equipment discharge insulation defects simulation experimental platform, ultrasonic - electromagnetic wave simultaneous sensing sensor performance testing, the experimental results show that the sensor can be developed at the same time accurately detect the ultrasonic and electromagnetic wave signals, the results of the research in this paper will significantly reduce the application cost of ultrasonic and electromagnetic wave detection device.

A simple and economic method to modify large organic surfaces for enhancing adhesion and transparent Au/PMMA with high electromagnetic shielding efficiency

This study introduces a simple and cost-effective approach for modifying large organic surfaces, facilitating robust adhesion between Au films and polymethyl methacrylate (PMMA) while retaining transparency to visible light and effectively shielding against electromagnetic interference (EMI). The proposed surface modification method employs a cheap low-power conventional UV lamp to illuminate organic surfaces in an open environment, rending it convenient and applicable for surfaces ranging from small to massive, irrespective of size, shape and location. By subjecting transparent PMMA glass to a brief 20–30 min exposure to a 36 W UV lamp positioned 5 cm away from the sample surface, the PMMA surface is dramatically modified and the surface is turned from hydrophobic to hydrophilic, establishing a strong adhesion between PMMA and Au films. The resulting Au/PMMA glass exhibits remarkable transparency about 70% within the visible light spectrum, coupled with an impressive EMI shielding efficiency that surpasses 20 dB across a broad range of electromagnetic wavebands, encompassing the S, C, X and Ku bands that correspond to the wave frequencies of major electromagnetic pollution and crucial applications of 5G communication, credit card validation, radar systems, traffic control, etc. Various characterizations have been conducted, elucidating the underlying mechanisms. This study presents an important advancement, and the accessible and scalable nature of the large-scalable surface modification method has far-reaching implications across numerous industrial sectors and applications, in addition to transparent EMI shielding Au/PMMA glasses.

Mid-infrared bimodal wide metamaterial absorber based on double-layer silicon nitride structure

Infrared band occupies a very important position in the electromagnetic wave band. Traditional infrared devices use the inherent properties of natural materials to achieve the regulation of electromagnetic waves, but the limited ability of such devices to regulate electromagnetic waves can't well meet our needs. In this paper, we reported a metamaterial absorber of Cr-Si3N4-Cr-Si3N4-Ti based on double-layer metal-insulator-metal (MIM). It is investigated with the optimal structural parameters of 490 nm, 330 nm, 30 nm, 720 nm, 120 nm, in descending order, at which the absorptive properties are studied. When the light wave is incident vertically, it can be obtained from the experimental simulation that this absorber has polarisation insensitivity. Because of the coupling effect of the surface plasmon resonance and the high-loss material, the bandwidth of absorption greater than 90% can reach 9190 nm, and the average absorption in the target long-wave infrared band (9.506∼18.145 μm) is 94.8%. By selecting different geometrical parameters of the structure, the absorption spectrum can be adjusted independently. In addition, the absorber has good incident angle insensitivity in TE and TM modes. Also, the absorber we proposed has a plain structure, is convenient for manufacturing, the material is easier to obtain, which ensures a good absorption bandwidth and average absorptivity, and the study of this metamaterial absorber has important applications in solar cells, satellite radiothermographs, photodetectors, and spectral imaging.

Optically compatible infrared camouflage performance of ITO ink.

With the rapid development of military reconnaissance technology, reconnaissance devices have been equipped with wideband reconnaissance ability, which imposes increased requirements on camouflage. Developing multiband camouflage materials with good compatibility has become increasingly important. Indium tin oxide (ITO), a transparent conductive oxide with good comprehensive photoelectric properties, exhibits different absorption, reflectivity, and transmission characteristics in different bands of electromagnetic waves. Therefore, ITO might be able to solve broadband and multiband camouflage problems effectively. In this paper, ITO is expressed as In32-xSnxO48. The energy band structure, optical properties, and infrared absorption spectra at different doping ratios of Sn (x = 0, 1, 2, 3) were obtained on the basis of first principle theory, and the camouflage mechanism of ITO in different electromagnetic wavebands was explored. Results demonstrated that when x = 3, specifically, when the doping ratio of Sn atoms was 9.375%, ITO had high transmission in the visible light band and infrared band reflectivity and can realize optically compatible infrared camouflage. In accordance with calculation results, ITO nanodispersion liquid (x = 3) was mixed with green camouflage coating added with some additives to prepare green ITO camouflage ink for silkscreen printing. The ink formed a camouflage protective ink coating after it was coated onto the surface of fabric through silkscreen printing. Results showed that the emissivity of the ITO ink coating decreased by more than 0.13 when its solid content reached 20%, and its camouflage performance in the visible light band was barely affected. The results of this research can guide the application of ITO materials in the field of camouflage.

Achieving the low emissivity of graphene oxide based film for micron-level electromagnetic waves stealth application

In recent years, the development of advanced materials with enhanced micron-level electromagnetic waves stealth properties has garnered significant attention due to their applications in fields such as military technology and thermal insulation. This study primarily investigates the stealth characteristics of materials within the 8–14 μm electromagnetic wave band, commonly known as the infrared (IR) spectrum. The effect of metallic Ag nanoparticles on the graphene oxide (GO) was obtained to achieve the excellent IR stealth ability. Specifically, Ag/GO composite films were prepared using a one-step reduction method and vacuum-assisted drying. The IR emissivity (8–14 μm) of the composites was significantly reduced with increasing Ag content, and the electrical conductivity of the materials was enhanced. When the Ag/GO mass ratio in the material was 1:2, the IR emissivity of the material at 8–14 μm was as low as 0.279, which was 62 % lower compared to GO. In addition, IR thermograms of the composites were analyzed using an IR thermographic camera. Obviously, the composites exhibited significant IR stealth properties when compared with those of GO. Thus, this work provides a reference for the preparation of carbon-based low IR emissivity materials for infrared stealth application.

Multifunctional-hierarchical flexibility metasurfaces for multispectral compatible camouflage of microwave, infrared and visible.

The prevalent use of multispectral detection technology makes single-band camouflage devices ineffective, and the investigation of technology for camouflage that combines multispectral bands becomes urgent. The multifunctional-hierarchical flexibility metasurfaces (MHFM) for multispectral compatible camouflage of microwave, infrared, and visible, is proposed, fabricated, and measured. MHFM is primarily composed of an infrared shielding layer (IRSL), a radar absorbing layer (RAL), and a visible color layer (VCL). Among them, IRSL can block thermal infrared detection, and RAL can efficiently absorb microwave band electromagnetic (EM) waves. The VLC can display black (below 28°C), purple (28°C∼31°C), green (31°C∼33°C), and yellow (above 33°C) at different temperatures to achieve visible camouflage. Simulation results show that MHFM can achieve absorption higher than 90% in the 2.9∼13.9 GHz microwave band. Theoretically, the emissivity of MHFM in the infrared spectral range 3∼14 µm is less than 0.34. In addition, the MHFM consists of high-temperature-resistant materials that can be used normally at temperatures up to 175°C, providing excellent high-temperature stability. The measurement results show that the camouflage performance of the MHFM is in excellent agreement with the proposed theory. This study proposes a new method for multispectral camouflage that has broad engineering applications.

Frequency combs generated from rotational Doppler effect

In frequency domain, power spectrum density with evenly spaced discrete lines forms a frequency comb, which has become a fundamental physical concept for wave. Especially, in optical electromagnetic wavebands, an optical frequency comb plays a crucial role for a variety of precision measurement technologies and has become one of the representative breakthroughs in modern physics. To extend the study of frequency comb to other wave region would be an interesting and important task. One significant challenge is to develop a general method suitable to different waves. Here, by manipulation one of the essence natures of wave, orbital angular momentum (OAM), we demonstrate an general approach to produce a frequency comb based on a rotational Doppler effect with the OAM comb. We experimentally generate and verify frequency comb with teeth up to 10. Our results not only provide a general way for the frequency comb generation suitable to various waves but also may open up possibilities for application of frequency comb in more types of wave.

Mechanical and dielectric properties of Si3N4-SiO2 ceramics prepared by digital light processing based 3D printing and oxidation sintering

Si3N4-SiO2 ceramics are considered as the preferred high-performance wave-transmitting material in the aerospace field. However, traditional fabrication methods for Si3N4-SiO2 ceramics have the disadvantages of high cost and complicated fabrication process. In this paper, Si3N4-SiO2 ceramics with excellent mechanical and dielectric properties were fabricated by digital light processing-based 3D printing combined with oxidation sintering. Firstly, the curing thickness and viscosity of slurries with different solid loadings for vat photopolymerization-based 3D printing were studied. Then, the effects of the sintering temperature on the linear shrinkage, phase composition, microstructure, flexural strength, and dielectric properties of Si3N4-SiO2 ceramics, and the influences of solid loading on them were explored. The curing thickness and viscosity of the slurry with a solid loading of 55 vol% were 30 μm and ∼1.5 Pa‧s, respectively. The open porosity and the flexural strength of Si3N4-SiO2 ceramic with a solid loading of 55 vol% were 4.3 ± 0.61% and 76 ± 5.6 MPa, respectively. In the electromagnetic wave band of 8–18 GHz, the dielectric constant of Si3N4-SiO2 ceramics was within the range of less than 4, and the dielectric loss remained below 0.09. The method of digital light processing-based 3D printing combined with oxidation sintering can be further extended in the preparation of Si3N4-based structure-function integrated ceramics.

Snake Scale-Inspired Poly(vinylidene fluoride)/Ti3CNTx@Polypyrrole Coatings for Ultrawide-Bandwidth Microwave and Visible Light Absorption.

The accuracy of data collected by optical instruments can be greatly impacted by radar band electromagnetic waves (EM) and scattered visible light. Traditional electromagnetic-wave-absorbing (EMA) materials face challenges in effectively attenuating electromagnetic waves within the visible light spectrum. To address this issue, a structural engineering-based assembly strategy was developed to construct PVDF/Ti3CNTx@PPyNF composites with multiple heterogeneous interfaces, inspired by snake scales. And through the self-doping of N elements and the coating process, the material finally exhibits excellent microwave and visible light absorption properties. This approach generates multiple polarization losses of electromagnetic waves, enabling the material to exhibit excellent electromagnetic wave absorption performance. Specifically, the PVDF/Ti3CNTx@PPyNF composite, containing 5 wt % Ti3CNTx@PPyNFs, demonstrates exceptional microwave absorption performance, with a minimum reflection loss of -65.5 dB and an effective absorption bandwidth of up to 6.95 GHz. Additionally, the composite coating exhibits 97.4% visible light absorption performance, providing a promising solution to the challenges of protecting against complex electromagnetic environments.

Thermally reconfigurable topological protection routes for the 2D phononic system

Tunable topological insulators (TIs) with active tunability of frequency or path and better adaptability to the dynamic environment than conventional TIs have attracted great interest recently. The research directions of tunable TIs are mainly in the frequency domain and spatial domain. However, the most current research is mainly based on the former. Obviously, the tunable spatial path can bring more degrees of freedom to the application of TIs. Here, we present a topological protection system realized by a thermally tunable elastic film composed of VO2 covered on a patterned substrate. The topological phase transition is induced by breaking the symmetry of the unit cell on the substrate, and we pre-define the topological protection paths in each direction on the substrate. The conduction or blocking of elastic waves is achieved by using the metal-insulator phase transition of VO2, which enables intelligent TIs with reconfigurable propagation paths and reconfigurable interfaces. In addition, the reconfigurable topological path and the thermal modulation are presented by numerical simulations. Such elastic topological materials and their corresponding devices will significantly promote the development of TIs and are expected to enable the coupling with communication band electromagnetic waves and the realization of light-induced non-contact thermal modulation.

Polarization insensitive metamaterial based electromagnetic multiband absorber in the long-wave infrared (LWIR) region

In this paper, we propose a design of metamaterials-based polarization insensitive, broadband electromagnetic (EM) wavebands absorber in the long-wave infrared (LWIR) region. The proposed model consists multilayer of gold-magnesium oxide-germanium-gold-germanium layers from the bottom to the top of the structure. The top surface of our proposed metamaterial structure consists of rings and disk-shape resonators. Using the finite element method, the electromagnetic properties of the metamaterials are investigated in terms of reflectance and absorbance. We find that excitation of localized surface plasmon resonance gives rise to highly localized electromagnetic resonance with the structure. Due to the circularly symmetric nature of the ring resonator, the numerical results show that the proposed design of metamaterial has average absorption (above 90 %) from 12.8 μm to 17.8 μm for both transverse electric (TE) and transverse magnetic (TM) polarization over a wide range of incidence angle. Along with this, it can absorb EM waves completely (100 %) at a particular wavelength of 9.1 μm and 17.8 μm. These results show the proposed model configuration may have wide application in energy harvesting and another optoelectronic area.

Epitaxial indium antimonide for multiband photodetection from IR to millimeter/terahertz wave

Conventional photodetection converts light into electrical signals only in a single electromagnetic waveband. Multiband detection technology is highly desirable because it can handle multispectral information discrimination, identification, and processing. Current epitaxial solid-state multiband detection technologies are mainly within the IR wave range. Here, we report epitaxial indium antimonide on gallium arsenide for IR and millimeter/terahertz wave multiband photodetection. The photoresponse originates from interband transition in optoelectrical semiconductors for IR wave, and surface plasmon polaritons induced nonequilibrium electrons for a millimeter/terahertz wave. The detector shows a strong response for an IR wave with a cutoff wavelength of 6.85 μm and a blackbody detectivity of 1.8 × 10 9 Jones at room temperature. For a millimeter/terahertz wave, the detector demonstrates broadband detection from 0.032 THz (9.4 mm) to 0.330 THz (0.9 mm); that is, from K a to the W and G bands, with a noise equivalent power of 1.0 × 10 − 13 W Hz − 1 / 2 at 0.270 THz (1.1 mm) at room temperature. The detection performance is an order of magnitude better while decreasing the temperature to 170 K, the thermoelectric cooling level. Such detectors, capable of large scale and low cost, are promising for advanced uncooled multiband detection and imaging systems.

Millimeter wave-terahertz substrate integrated waveguide transition structure based on low temperature co-fired ceramic

In a microwave circuit system, the discontinuity caused by electromagnetic wave entering into another transmission medium from one transmission medium will greatly affect the transmission performance of the system, which has always been the focus of microwave circuit design. When the electromagnetic wave band enters into the millimeter wave and terahertz band, how to realize the efficient and low loss transmission of electromagnetic wave from the metal rectangular waveguide interface to the dielectric substrate is the key to the realization of millimeter wave terahertz communication system. Substrate integrated waveguide to rectangular waveguide transition structure is an important structure connecting waveguide interface and planar circuit in millimeter wave and terahertz communication system, and it is the basis of designing planar antenna array. In this paper, a W-band and D-band substrate integrated waveguide to rectangular waveguide transition structure is designed, which improves the transmission performance and expands the bandwidth through the stepped structure. On this basis, a one-in-two divider structure is designed, with an empty cavity structure used to reduce the loss and expand the bandwidth. These two structures have the characteristics of simple structure and easy processing, and their practicalities are verified by simulation optimization and actual low temperature co-fired ceramic substrate processing and assembly test. The actual test results show that the substrate integrated waveguide to rectangular waveguide transition structure can achieve a return loss of less than –10 dB in a frequency ranges of 126–149 GHz and 112–139 GHz, the one-in-two divider structure can achieve a return loss of less than –10 dB in the frequency band of 132–155 GHz.

ABSORPTION OF ELECTROMAGNETIC WAVES WITH VARIOUS WAVELENGTH BY NANOPARTICLES

An aim of the article is to review the potential of nanotechnology in military for the development of stealth technologies. Methods. Analysis of information, synthesis, generalization and comparison. Results. An overview of nanoparticles use in the development of stealth technologies has been made. Foreign and Ukrainian publications were analyzed. The possibility of using nanoparticles of metals like iron, cobalt, nickel, zinc, manganese and other metals and composite nanomaterials for absorption, refraction and scattering of waves of different lengths and frequencies, which can be used in the development of coatings for military equipment to reduce visibility and counter targeting systems has been shown.
 The possibility of using nanoparticles of nonmetals to absorb infrared radiation, which is important for masking equipment, military facilities and personnel, has been highlighted.
 High-tech weapons, technical means of detection and guidance are constantly being modernized and improved. One of the most important conditions for tactical superiority over the enemy is camouflage and counteraction to these systems. One of the ways to increase the resistance to detection and guidance systems is the development of stealth technologies based on nanoparticles of metals and non-metals.
 In the long run, nanotechnology and stealth coating should ensure the invisibility of objects in a wide frequency band of electromagnetic waves, which can reach two to three orders of magnitude. These are ambitious tasks, however, they are real.
 Foreign and domestic scientists have proven the possibility of using nanoparticles of metals and composite materials to develop coatings with the ability to absorb electromagnetic waves in a wide range, which can be used in the development of coatings to counter radar stations and other detection systems.
 Given the significant scientific potential of Ukrainian scientists, presence of technologies needed for the synthesis of nanoparticles of metals and nonmetals of various shapes and sizes, based on previous research on the ability of nanoparticles to absorb waves of different lengths and frequencies, we see high prospects for stealth technologies for the Military Forces of Ukraine.

MOF-derived NiFe2S4/Porous carbon composites as electromagnetic wave absorber

The preparation of strong absorption, thin thickness and wide band electromagnetic wave absorbers has always been the focus of research. In this paper, NiFe2S4/PC composites, an electromagnetic wave absorbing material with excellent performance, is prepared by introducing Ni-MOF, Fe and S elements into porous carbon framework. The material has a minimum reflection loss (RLmin) of −51.41 dB and the matching thickness is only 1.8 mm. In addition, the effective absorption bandwidth (EAB) is 4.08 GHz when the thickness is 1.9 mm. The rich interface and good impedance matching characteristics are the main reasons for the excellent absorbing performance of the material. The experimental results show that NiFe2S4/PC composites is a reasonable and effective electromagnetic wave absorption material.

Enhanced properties of CoS2/Cu2S embedded N/S co-doped mesh-like carbonaceous composites for electromagnetic wave absorption

CoS2/Cu2S embedded N/S co-doped mesh-like carbonaceous composites with enhanced electromagnetic wave absorbing performance was successfully prepared using carboxymethyl cellulose hydrogel spheres as starting materials by freeze-drying and high-temperature carbonization, in which thiourea as a source of N/S was favorably achieved. This newly designed three-dimensional mesh-like structures embedded with CoS2 and Cu2S nanoparticles was confirmed by various techniques, while the N/S co-doped carbonaceous matrix, would contribute to the enhancement of electron transport, interfacial polarization, dipole polarization, ferromagnetic resonance, and magnetic coupling. This unique three-dimensional mesh structure facilitates multiple reflections and scattering of electromagnetic waves within the single matrix. By adjusting the dosage ratio between components and the filling amount of filler, the composite material exhibited a good impedance matching, which promotes the synergy between conductive loss, dielectric loss, and magnetic loss, and improves the electromagnetic wave loss. When the composite is filled with 25 wt%, there is a minimum reflection loss value of −51.68 dB at 5.20 GHz, and when the coating thickness is 4.5 mm, the effective absorption bandwidth is 3.84 GHz when the coating thickness reaches 2.0 mm. The experimental results illustrated that the synthesized composites might be alternative materials for low-frequency band electromagnetic wave absorption.

Very large group delay in VHF band using coupled high temperature superconducting resonators

Storing a very high frequency (VHF) band (30–300 MHz) electromagnetic wave has many potential applications, such as phase modulation, buffering, and radio frequency memory. It can be effectively achieved by applying coupled resonator-based electromagnetically induced transparency (EIT) due to its slow light effect. However, the wavelength in the VHF band is too long to design resonators, and the group delay is limited by the high resistive loss of metal. The practical application of EIT in the VHF band is still a big challenge. In this work, we propose and experimentally demonstrate EIT response in a high-temperature superconducting (HTS) microwave circuit with coupled-resonator-induced transparency. The chip size of the HTS circuit is only 34 mm × 20 mm with a very low transparency frequency of 198.55 MHz. In addition, we implement very large group delay higher than 12.3 μs and 16.2 μs with working temperatures of 65 K and 50 K separately, which is much longer than the previous reported works on slow wave. The fabricated circuit is planar with working temperature about 65 K, and thus can be easily integrated into other microwave devices under the cryogenic conditions provided by a commercial portable Stirling cryocooler. Our proposed method paves a way for studying EIT in the microwave region due to the high quality factor of the HTS resonator, which has great potential use for radio-frequency memory in the future.

Comparison of the influence of Martian and Earth's atmospheric environments on terahertz band electromagnetic waves

SummaryTerahertz waves have wide application prospects in space communication because of their strong penetration ability, wide band, and strong directional antenna. Therefore, it is necessary to study the propagation characteristics of terahertz waves in space, such as in the environment on Mars. In space near Mars, the terahertz link is mainly affected by the absorption attenuation of its atmosphere and the scatter attenuation of heavy dust storms. In this paper, the absorption of 0.1–1 THz waves in the Martian atmosphere is analyzed. The absorption coefficient is calculated based on the theory of atmospheric radiative transfer and the HITRAN database. The influence of temperature, pressure, and altitude on the absorption coefficient is analyzed, and the calculation results are compared with those of Earth's atmosphere. The size distribution of Martian dust particles is then fitted by lognormal distribution, and the transmission characteristics of terahertz waves with different wavelengths are studied based on Mie theory. The research results show the transparent window positions of the attenuation peaks of water vapor and oxygen, which are the main factors of atmospheric transmission attenuation in the 0.1–1 THz band. The attenuation of Martian dust is affected by the size parameter, and it decreases with the visibility of the dust storm. The results provide a reference for terahertz communications in a Martian atmospheric environment and clarify the range of Martian atmospheric fading and dust fading.