Conversion Of Electromagnetic Waves Research Articles

Unification of Gravity and Light Using the Gertsenshtein Effect

This study examines the Gertsenshtein effect, which theorizes the conversion of electromagnetic waves into gravitational waves in the presence of a strong magnetic field. First proposed by Mark Gertsenshtein in 1962 and grounded in general relativity, this effect forms a bridge between electromagnetism and gravity, providing insights into the fundamental interactions within spacetime. Through the use of Maxwell's and Einstein's equations, we analyze the conditions necessary for this conversion and discuss its theoretical significance as well as the challenges in observation. Given the inherently weak nature of gravitational waves, their detection proves difficult; however, the Gertsenshtein effect holds the potential to shed light on cosmic events and the structure of the universe. This paper elucidates the physics of the effect, its astrophysical and cosmological implications, and the pathway toward experimental verification. It concludes that, in the context of the Gertsenshtein effect, gravity and light—similar to mass and energy in the special theory of relativity—are different manifestations of the same fundamental essence of the universe.

Wave-heat-electricity conversion: Design and analysis of an electromagnetic energy conversion device

An innovative electromagnetic energy harvester was developed using a compact four-ring single-resistor unit cell. To achieve efficient conversion of electromagnetic waves into electricity, we integrated the high-performance Bi2Te3 thermoelectric material onto the load resistor. Remarkably, this unit cell exhibits exceptional energy harvesting capabilities at a frequency of 5.8 GHz while maintaining polarization insensitivity. Through comprehensive analysis, we evaluated the energy harvesting efficiencies, power loss distribution, and current density distribution. Additionally, we investigated the impact of incident power on the unit cell's temperature and energy conversion efficiencies. To enhance energy concentration on the load, we ingeniously designed an “L-shaped” metal through-hole structure within the four-ring single-resistor unit cell. Our results demonstrate that the four-ring single-resistor unit cell achieves an impressive harvesting efficiency of 94.5% at 5.8 GHz, with a thermal conversion efficiency of 43.3 °C/W, an electrical conversion efficiency of 0.23 mV/°C, and an electrical response rate of 9.4 mV/W. Notably, when subjected to a power input of 7 W, the unit cell produces an output voltage of 65.9 mV, and its theoretical maximum output power reaches 180 mW.

Staggered circular nanoporous graphene converts electromagnetic waves into electricity

Harvesting largely ignored and wasted electromagnetic (EM) energy released by electronic devices and converting it into direct current (DC) electricity is an attractive strategy not only to reduce EM pollution but also address the ever-increasing energy crisis. Here we report the synthesis of nanoparticle-templated graphene with monodisperse and staggered circular nanopores enabling an EM–heat–DC conversion pathway. We experimentally and theoretically demonstrate that this staggered nanoporous structure alters graphene’s electronic and phononic properties by synergistically manipulating its intralayer nanostructures and interlayer interactions. The staggered circular nanoporous graphene exhibits an anomalous combination of properties, which lead to an efficient absorption and conversion of EM waves into heat and in turn an output of DC electricity through the thermoelectric effect. Overall, our results advance the fundamental understanding of the structure–property relationships of ordered nanoporous graphene, providing an effective strategy to reduce EM pollution and generate electric energy.

Full-space polarization conversion of electromagnetic waves at terahertz frequency based on metasurface

In this paper, a full-space electromagnetic wave polarization converter working in the terahertz frequency was put forward, and its physical mechanism was also analyzed. The polarization converter could realize the reflection cross-polarization conversion in the frequency range of 3.16–3.75 THz, with the Polarization Conversion Rate (PCR) of more than 90%. In the frequency range of 0.43–2.15 THz, it could realize transmission cross-polarization conversion, with the PCR close to 100%. In short, the designed metasurface polarization converter has a simple structure, realizes full-space manipulation of electromagnetic waves, facilitates the miniaturization and integration of the system, and has the potential applications in antennas, imaging systems, remote sensors, and radiometers.

A Tunable Multi-Mode Dual-Band Terahertz Polarization Converter

The polarization conversion of electromagnetic waves plays a crucial role in practical application. Here, a tunable multi-mode dual-band high-efficiency and reflection-type polarization converter based on liquid crystal (LC) in the terahertz region is proposed. It is composed of periodic unit structures, each unit of which is constituted by the designed structure, LC mixture and fully reflected gold mirror. It numerically reveals that in the operating bandwidth 1.03–1.53 and 1.27–1.86 THz corresponding to the refractive index of LC mixtureñoandñe, the converter can convert linear-polarized and circular-polarized waves to its corresponding cross-polarizations, whose polarization conversion ratio is larger than 90%. Meanwhile, the proposed converter can realize the conversion from linear-polarized wave to circular-polarized one in dual-band, 1.10–1.25 and 1.92–2.2 THz or 0.93–1.04 and 1.57–1.88 THz corresponding toñoandñewith axis ratio lower than 3 dB. The insensibility of incident angle is analyzed as well. In addition, the physical mechanism of the polarization conversion is disclosed. The ultra-thin and compactness characteristic of this designed polarization converter are very attractive for a variety of applications in EM measurement, sensing, terahertz technology and 6G communication.

Ultra-wideband tunable reflective linear-to-circular polarization converter realized by GST-based metasurface at terahertz frequency

Polarization conversion of electromagnetic wave plays an important role in practical application. In this paper, a terahertz band ultra-wideband tunable linear-to-circular polarization converter based on GST metasurface is proposed. It consists of two triangular metals, a phase change material (GST), a dielectric plate and a metal floor. The proposed polarization converter can convert linearly polarized waves into circularly polarized waves in different frequency bands by controlling the crystallization state of GST through temperature, without the need of re-optimization and remanufacturing structure. It has the characteristics of ultra-wideband and high efficiency. The proposed polarization converter has potential for miniaturization and integration of terahertz systems.

Transmission of layered nanoresonators including epsilon-near-zero metamaterials: interference-enabled opportunities to realize ultrathin polarization converters

Polarization conversion of electromagnetic waves transmitted through multilayer nanoresonators, including a main homogeneous layer made of a transparent uniaxial dielectric sandwiched between epsilon-near-zero and metallic spacer layers, has been analytically modeled. The numerical analysis, based on exact solutions of electromagnetic boundary problems, confirms opportunities to use such multilayers as utracompact polarization converters (in particular, zero-order quarter and half waveplates) of a new type. The proposed systems are characterized by much wider ranges of parameters and significantly reduced (nanometric) thicknesses in comparison with the conventional waveplates. The operation regimes, resulting from the features of amplification of proper wave phase differences under multibeam interference conditions, are considered. The concept can be realized for both metamaterial-dielectric-metamaterial and metal-dielectric-metal structures and used for the development of ultrathin, large area, and simple in fabrication polarization devices for photonic applications.

Thermally switchable bifunctional plasmonic metasurface for perfect absorption and polarization conversion based on VO2.

Perfect absorption and polarization conversion of electromagnetic wave (EM) are of significant importance for numerous optical applications. Vanadium dioxide (VO2), which can be converted from insulating state to metallic state by being exposed to different temperatures, is introduced into a metallic square loop to constitute a switchable bifunctional plasmonic metasurface for perfect absorption and polarization conversion. Combined theoretical analyses and numerical simulations, the results show that at temperature T = 356 K, the metasurface acts as a perfect absorber with nearly 91% absorptance at the wavelength of 1547 nm. When the temperature decreases to T = 292 K, the metasurface expresses as a high efficiency (about 94%) polarization converter with the polarization conversion ratio up to 86% around 1550 nm. The designed bifunctional metasurface has plenty of potential applications such as energy harvesting, optical sensing and imaging. Moreover, it can also provide guidance to research tunable, smart and multifunctional devices.

An efficient terahertz polarization converter with highly flexible tunability over an ultra-broad bandwidth

The polarization control and conversion of electromagnetic waves is of vital importance in many practical applications and experimental systems. For terahertz waves that cover a broad frequency range of 0.3–10 THz, an operation with high spectral tunability is essential, especially for spectroscopic applications. In this paper, we propose a very simple yet efficient experimental apparatus to convert a linearly polarized beam into a circularly polarized or even an elliptically polarized beam, with high efficiency (>90%) and ultrabroad bandwidth (0.3–10 THz) tunability in the terahertz region. The proposed polarization converter, consisting of only a wire-grid polarizer and a mirror, is convenient and flexible to use in the experimental setup in the laboratory. We expect that it can find broad applications in advanced spectroscopy systems like terahertz ellipsometry where an elliptically polarized beam is needed.

Crystal structure dependence of red to green light emission by LaOF : Yb3+/Er3+ up-conversion phosphor

Up-conversion (UC) is the conversion of electromagnetic waves from long to short wavelengths. In this study, near-infrared rays (with wavelengths of 980 nm) were upconverted to visible light rays (with wavelengths of 400–750 nm), and the UC luminescence characteristics of lanthanide-doped materials were measured and analyzed. LaOF : Yb3+/Er3+ UC phosphor samples were fabricated by using LaF3 (hexagonal), Yb2O3 (cubic), and Er2O3 (cubic) powders. The mole ratio of La : Yb : Er was 1 : 0.01 : 0.01, and LaOF : Yb3+/Er3+ was obtained by baking these materials. The UC emission of yellow to green light was confirmed by the overlapping of green and red light. The emitted light intensity was the highest for the sample baked at 1100 °C for 2 h. Furthermore, x-ray diffraction (XRD) results revealed that the photoluminescence emission intensity increased with increasing integrated intensity of the tetragonal LaOF crystal system.

Polymeric Materials for Conversion of Electromagnetic Waves from the Sun to Electric Power.

Solar photoelectric energy converted into electricity requires large surface areas with incident light and flexible materials to capture these light emissions. Currently, sunlight rays are converted to electrical energy using silicon polymeric material with efficiency up to 22%. The majority of the energy is lost during conversion due to an energy gap between sunlight photons and polymer energy transformation. This energy conversion also depends on the morphology of present polymeric materials. Therefore, it is very important to construct mechanisms of highest energy occupied molecular orbitals (HOMO)s and the lowest energy unoccupied molecular orbitals (LUMO)s to increase the efficiency of conversion. The organic and inorganic solar cells used as dyes can absorb more photons from sunlight and the energy gap will be less for better conversion of energy to electricity than the conventional solar cells. This paper provides an up-to-date review on the performance, characterization, and reliability of different composite polymeric materials for energy conversion. Specific attention has been given to organic solar cells because of their several advantages over others, such as their low-energy payback time, conversion efficiency and greenhouse emissions. Finally, this paper provides the recent progress on the application of both organic and inorganic solar cells for electric power generations together with several challenges that are currently faced.

Scattering and polarization conversion of electromagnetic waves obliquely incident on a magnetized plasma layer

This paper addresses the scattering of electromagnetic waves obliquely incident on a magnetized plasma layer. It is shown that the polarizations of the waves can be converted when they are obliquely incident on a magnetized plasma layer. The scattering coefficients of the incident and converted waves are computed based on the analytic solutions of a uniform magnetized plasma slab. The total transmittance and reflectance are similar to those of the normal incidence, but the individual scattering coefficients of the incident and converted waves vary, depending on the dispersion characteristics of the ordinary and extraordinary modes in the plasma. The contributions of the converted wave increase with the wave number parallel to the magnetic field but decrease as the frequency increases above the upper hybrid resonance, regardless of the parallel wave number.

Effects of a random spatial variation of the plasma density on the mode conversion in cold, unmagnetized, and stratified plasmas

We study the effects of a random spatial variation of the plasma density on the mode conversion of electromagnetic waves into electrostatic oscillations in cold, unmagnetized, and stratified plasmas. Using the invariant imbedding method, we calculate precisely the electromagnetic field distribution and the mode conversion coefficient, which is defined to be the fraction of the incident wave power converted into electrostatic oscillations, for the configuration where a numerically generated random density variation is added to the background linear density profile. We repeat similar calculations for a large number of random configurations and take an average of the results. We obtain a peculiar nonmonotonic dependence of the mode conversion coefficient on the strength of randomness. As the disorder increases from zero, the maximum value of the mode conversion coefficient decreases initially, then increases to a maximum, and finally decreases towards zero. The range of the incident angle in which mode conversion occurs increases monotonically as the disorder increases. We present numerical results suggesting that the decrease of mode conversion mainly results from the increased reflection due to the Anderson localization effect originating from disorder, whereas the increase of mode conversion of the intermediate disorder regime comes from the appearance of many resonance points and the enhanced tunneling between the resonance points and the cutoff point. We also find a very large local enhancement of the magnetic field intensity for particular random configurations. In order to obtain high mode conversion efficiency, it is desirable to restrict the randomness close to the resonance region.

Polarization conversion of electromagnetic waves by Faraday chiral media

The reflection of a normally incident plane wave due to the interface between vacuum and a Faraday chiral medium (FCM) supported by a perfect electric conductor was rigorously derived. Numerical results strongly indicated that arbitrary polarization conversions are realizable from the incident plane wave to the reflected plane wave by properly choosing the constitutive parameters of the FCM.

Collisional/resonance absorption in cold/warm magnetized plasmas of the F-region high-latitude ionosphere

[1] The collisional/resonance absorption due to linear mode conversion of electromagnetic waves into electrostatic/plasma waves is studied in cold/warm magnetized plasmas relevant to the F-region of the high-latitude ionosphere. The absorption coefficient is calculated numerically using a full-wave model for high-frequency waves incident normally/obliquely to the direction of inhomogeneity. The absorption coefficient of collisional cold plasmas is found to be independent of the collision frequency in the small range of incidence angles near the critical angle; whereas, outside this range absorption increases with increasing collisions. In warm collisionless plasmas, the resonance absorption coefficient is shown to be independent of the electron temperature values pertinent to the F-region plasma. We have demonstrated for the first time a strong effect of the external magnetic field arbitrarily oriented in the plane of incidence on the absorption coefficient, which is not pronounced in the limit of weakly magnetized plasmas.

Doppler frequency up conversion of electromagnetic waves in a slotline on an optically excited silicon substrate

The Doppler frequency up conversion of microwaves in a slotline on an optically excited silicon substrate was experimentally observed. An array of 24 optical fibers with different lengths was used to effectively tilt the wave front of a 532 nm neodymium-doped yttrium aluminum garnet laser beam with a pulse duration of 33 ps. The tilted laser beam produced electron-hole surface plasma whose boundary moved at a relativistic velocity of about c/3.4 (c is the speed of light) along the slotline. The experiments showed that microwaves reflected at the moving boundary of the plasma in the slotline are converted to millimeter waves with a frequency up conversion ratio of 3.82.

Excitation and conversion of electromagnetic waves in pulsar magnetospheres

We demonstrate that nonlinear decay of obliquely propagating Langmuir waves into Langmuir and Alfvén waves (L --> L' + A) is possible in a one-dimensional, highly relativistic, streaming pair plasma. Such a plasma may be in the magnetospheres of pulsars. It is shown that the characteristic frequency of generated Alfvén waves is much less than the frequency of Langmuir waves and may be consistent with the observational data on the radio emission of pulsars.

Numerical Research of Mode Conversion in an Inhomogeneous Plasma

The linear mode conversion of electromagnetic waves in the hot, unmagnetized inhomogeneous plasma is studied numerically for different density profiles, and the dependence of the absorption coefficient on the incident angles and the wave frequencies are obtained for different electrons' temperature. The results show that the shapes of the density profiles and the electron's temperature create a certain effect on the coefficients of absorption, which reaches its peak value (about 50%) for appropriate parameters. Effective absorption occurs in a limited range of parameter q.

Linear conversion of electromagnetic waves into electron Bernstein waves in an arbitrary inhomogeneous plasma slab

A theory of coupling between electromagnetic and electron Bernstein waves in a plasma slab is presented. The theory uses an approach that associates the linear mode conversion with the singularity of the cold plasma wave equation at the upper hybrid resonance (UHR). The singularity results in linear interaction of cold plasma (electromagnetic) and hot plasma (Bernstein) modes. Applicability of the WKB theory to interacting modes is not required. In this method the full solution of the mode conversion problem including calculation of the excited Bernstein wave complex amplitude is reduced to finding a solution to the cold plasma wave equation, which describes dissipative wave power absorption at the UHR. This method is applicable to a variety of plasma configurations practically without limitations on the inhomogeneity scale-length. It permits one to consider in the framework of a single procedure particular cases like direct tunnelling of the incident wave, O–X–B conversion and transformation of the X-mode launched from the high-field side of a tokamak and having free access to the UHR.

Total polarization conversion in a two-dimensional electron system under cyclotron polariton resonance conditions

The polarisation conversion of a linear polarised electromagnetic wave incident onto a two-dimensional (2D) electron system at an angle is theoretically studied. We consider the 2D system located at the interface between two dielectric media with different dielectric constants. An external dc magnetic field is assumed to be directed along the normal to the 2D electron layer. In such a configuration the cyclotron-polaritons (CPs) in 2D electron system can be excited with the frequencies in the vicinity of the cyclotron frequency. Under the CPs excitation the resonance polarisation conversion of electromagnetic wave greatly increases in the system. In the absence of the electron scattering in 2D system, the polarisation conversion reaches 100% at a certain value of the angle of incidence which is more than the total reflection angle. Extremely high polarisation conversion takes place in a quite wide range of variation of the angle of incidence. High polarisation conversion efficiency (above 80%) remains when the actual electron scattering in the 2D system on GsAs is taken into account. The considered phenomena may be taken up in polarisation spectroscopy of 2D electron systems.