External Electromagnetic Wave Research Articles

Modulating surface plasmon resonance response by an external electromagnetic wave

We fabricated a highly sensitive layered structure of organic molecules and studied the influence of polarization of the external electromagnetic (EM) wave on the surface plasmon resonance response from the layered structure. The layered structure was formed by depositing a self-assembled monolayer (SAM) of mercaptoundecanoic acid (MUA) followed by a single layer of Langmuir-Schaefer (LS) film of traditional calamitic liquid crystal molecule, 4-octyl-4-biphenylcarbonitrile (8CB). The SAM of MUA was found to be non-responsive towards the change in resonance angle (RA) of surface plasmon resonance (SPR) due to the change in polarization of the external EM wave. However, such layer provides a soft-surface platform for the single layer of 8CB molecules which gets perturbed locally due to the incidence of the external EM wave. We obtained an oscillatory modulation of the change in RA due to the change in polarization angle of the EM wave with respect to the plane of incidence. The magnitude of sensitivity was found to be ∼4 milli°/° angle of polarization of the external EM wave. This study strongly suggests that sensitivity of a SPR-based sensor can be controlled by altering the linear state of polarization of the incident external EM wave.

EMI Analysis of Multiscale Transmission Line Network Using a Hybrid FDTD Method

A hybrid time-domain numerical method based on the full wave finite-difference time-domain (FDTD) method combined with a modified 1-D FDTD method has been proposed to analyze the electromagnetic interference (EMI) of multiscale transmission line networks in a metallic cabin in this article. This method is implemented through two numerical solvers for full wave and transmission line simulations, respectively, by adopting a set of reasonable physical boundary conditions between external fields and transmission line network. By using Ampere's law, the external fields can be transferred to a voltage source that can be further used as the forcing terms in the telegraph equation of the transmission line network. To overcome the challenge introduced by the multiscale size of the transmission line network, we combine 1-D explicit and implicit FDTD methods together to solve the coaxial cables and interconnects in PCB, respectively. Thus, among different subdomains, the hybrid method can be carried with the same time step without the restriction of the stability condition. Numerical examples show the accuracy as well as efficiency of the proposed method compared with the HSPICE and traditional FDTD method. In addition, the method is used successfully in analyzing the EMI effects of a complex transmission line network inside a cabin illuminated by external electromagnetic wave.

Nanoparticles in enhancing microwave imaging and microwave Hyperthermia effect for liver cancer treatment

Abstract Hyperthermia therapy is a promising therapy for liver cancer treatment that utilizes external electromagnetic waves to heat the tumor zone to preferentially kill or minimize cancer cells. Nevertheless, it’s a challenge to realize localized heating of the cancer tissue without harming the surrounding healthy tissue. This research proposes to utilize nanoparticles as microwave absorbers to enhance microwave imaging and achieve localized hyperthermia therapy. A realistic 3D abdomen model has been segmented using 3D Slicer segmentation software, and then the obtained segmented CAD model exported to Computer Simulation Technology (CST STUDIO) for applying the Finite Element Modeling (FEM). Next investigating both imaging and treatment capability. Finally, the specific absorption rate (SAR) and temperature distribution were computed without nanoparticles and with different types of nanoparticles such as gold (GNPs) and silver nanoparticles at frequency 915 MHz. By comparing the achived results, it was seen that Silver nanoparticles can make a great enhancement in raising the temperature. However, this result was unsatisfactory but, after adding gold nanoparticles the temperature exceed 42°C, at frequency 915 MHz which is achieving the hyperthermia treatment without harming the nearby healthy tissue, GNPs also can achieve a great enhancement in SAR result

Parametric resonance in the ultracold Rydberg plasma under the influence of an acoustic wave

The article considers weakly ionized ultracold Rydberg plasma under the influence of an acoustic wave of the terahertz range. The effect of an acoustic wave on Langmuir oscillations of Rydberg plasma is described using a hydrodynamic approach. The mechanism of the influence of an acoustic wave on Langmuir oscillations in such plasma, which consists in the scattering of electrons by neutral atoms oscillating in a high-frequency acoustic field, is considered. The unitary Kramers—Henneberger transformation in the Schrцdinger equation is used to calculate the cross section for the scattering of electrons by atoms performing high-frequency oscillations in the field of a terahertz acoustic wave. On this basis, a deep analogy is shown between the problem of scattering of an electron in the field of an external electromagnetic wave by a stationary atom and the problem of scattering of an electron by an atom vibrating in an external acoustic field. Numerical calculations demonstrate the oscillatory character of the cross section for the scattering of an electron by a Rydberg atom vibrating in a high-frequency acoustic field. Within the framework of the chosen hydrodynamic model, in view of the time dependence of the cross section for scattering of electrons by plasma atoms, the change in the electron density in such a system is described by the Mathieu equation, well known in mathematical physics. On the basis of this equation, the fundamental possibility of the appearance of parametric resonance, in the form of the buildup of Langmuir oscillations, in such a system is shown theoretically. The conditions for the appearance of resonance in Rydberg plasma initiated by a high-frequency acoustic wave are indicated.

Development of a heart rate detection algorithm using a non-contact doppler radar via signal elimination

Non-contact heart rate measurement is more convenient than conventional ECGs. So, a number of algorithms have been investigated to measure non-contact heart rate using a Doppler radar. However, elimination of environmental noise is still a challenge. We propose algorithms applying new filtering methods to efficiently detect the Heart rate. The Signal Elimination (SE) facilitates noise acquisition gradually and eliminates it from the previous signal. First, low-frequency noise is acquired from the original signal and removed from it. Second, high-frequency noise is acquired and removed from the previous signal. The Heart rate is then detected via differential polarization and threshold values. Experiments to assess the performance of the Heart rate detection algorithm were conducted on five subjects in a shielded room blocked from external electromagnetic wave. The algorithm has a mean sensitivity of 97.8 %, a positive predictivity of 96.2 %, and an error of 1.6 % compared with the Heart rate count in the reference Biopac. The performance of the proposed algorithm was better than that of the recently studied Heart rate detection algorithm using Doppler radar. Compared with Biopac, the Doppler radar facilitated a robust detection of the heart rate suggesting that the Doppler radar is an effective alternative to contact electrocardiogram in patients with burns or physical disorders.

A Compact, Wide Bandwidth Real-Time RF Exposure Setup Based on Microelectrode Array

A real-time RF exposure setup for studying the mechanism of RF biological effects based on microelectrode array (MEA) is proposed in this letter. The reflection simulation and measurement of the exposure setup show that the exposure setup has a wide working bandwidth in the frequency range of dc-3.0 GHz. The specific adsorption rate (SAR) measurement and simulation results at some frequencies show that the SAR distributions in the electrode region are relatively uniform. The test of the real-time effects on neuron activities at the SAR of 2.2 W/kg with a continuous 2.45-GHz RF signal injection was carried out. The results show that most of the electrodes can work normally and will not be affected by electromagnetic field noise. Additionally, the setup is compact and the system with MEA platform is almost covered by metal, which would significantly improve the ability to isolate the internal and external electromagnetic waves.

Optical Forces Acting on a Double DNA-Like Helix, Its Unwinding and Strands Rupture

In this paper we study electromagnetic forces induced on DNA and DNA-like helices by external electromagnetic waves. We consider simultaneously occurring forces and torques, interconnected and acting along the double helix axis. Since the DNA molecule has an absorption band in the ultraviolet and visible range near wavelengths λ1res=280 nm and λ2res=500 nm, we expect that it may be possible to selectively apply engineered forces to DNA molecules using appropriate illumination by light in these frequency ranges. The optical forces are simulated for DNA fragments consisting of 20 and 35 turns. Fragments of this length are convenient for direct sequencing and subsequent use in experiments and in practice. It is shown that repulsion forces can arise between the strands of the double DNA-like helix in the field of external electromagnetic waves. Such forces are characteristic of a DNA-like helix with its specific pitch angle and are not inherent in double helices with more straightened or more compressed turns. These repulsion forces, acting along the entire helix, both for electric charges and for electric currents, can lead to damage and rupture of the strands in the double helix. In addition, there can also exist forces and moments of forces directed along the helix axis, which simultaneously stretch and unwind a double helix. The double helix equilibrium under the action of optical forces is also of interest from another point of view, i.e., for optimizing the structure of artificial magnetics and bianisotropic metamaterials for applications in all frequency ranges.

Research and application of finite-element time-domain method for transient response of buried cable excited by an electromagnetic wave

To analyze electromagnetic (EM) transient responses of a buried cable, an accurate and reliable time-domain method is proposed in this paper. The approach is based on the transmission line (TL) second-order telegrapher’s current equation, and the expressions of ground impedance and admittance at higher frequencies are used to obtain the discrete finite-element time-domain (FETD) equations for the cable. Finally, transient responses at termination loads of the buried cable are obtained based on the global FETD equation, which is assembled using discrete FETD equations on all intervals. The accuracy and effectiveness of the proposed FETD method are demonstrated by comparing numerical results to those of the finite-difference time-domain (FDTD) method. The proposed method is also employed to investigate the effects of numerous parameters on transient currents of the buried cable, including the soil conductivity, buried cable depth, and incident and polarization angles of the external EM wave.

Bound Electron Transitions under the Influence of Electromagnetic Wave in Constant Magnetic Field

Motion and radiative transitions of an electron in a magnetic field under the influence of an external electromagnetic wave are studied for various confining conditions in semiconductor, graphene, in quantum wells, and relativistic generalization in terms of the Klein–Gordon equation are considered. In particular, the following problems are discussed. The so-called cyclotron resonance, which may appear in graphene, is studied with indication for appearance of the so-called frequency-halving. The problem is solved for two-dimensional massless charged particle, whose gapless nature is protected by sublattice symmetry. The exact classical calculation of this effect is undertaken in the framework of a 2D classical equation for a zero-mass electron. We also find an exact solution of the Schrödinger equation for charge carriers in semiconductors under the influence of an external magnetic field and in the field of electromagnetic wave with an account for their radiative transitions. Solutions of the relativistic Klein–Gordon equation in this configuration of electromagnetic fields are found as a certain generalization of the results obtained for the non-relativistic case. These results may serve as a first step for further efforts to find exact solutions of wave equations for quasiparticles in solid state structures in external fields.

Peculiarities of extremely short optical pulses propagation in carbon nanotube medium with nonlinear absorption

In this paper, we study the propagation of extremely short electromagnetic pulses in a medium with zig–zag carbon nanotubes taking into account pumping and nonlinear absorption introduced phenomenologically. Based on Maxwell’s equations, we obtain an effective equation for the vector potential of the electromagnetic field, which takes into account the dissipation of the pulse field under the conditions of the piezoelectric effect associated with the vibrations of heavy nuclei of the medium, pumping by an external electromagnetic wave, and nonlinear absorption of carbon nanotubes. We demonstrate the stability of the electromagnetic pulse shape on a time scale that is significantly longer than the pulse duration but not exceeding the relaxation time.

Bianisotropy for light trapping in all-dielectric metasurfaces

Magnetoelectric dipole coupling effects in all-dielectric metasurfaces composed of particles with bianisotropic electromagnetic response are investigated. This bianisotropic response is associated with the trapped mode excitation. Maintaining the trapped mode resonant conditions allows one to sufficiently increase the quality factor and reduce radiation losses in all-dielectric nanostructures (metasurfaces). An analytical model accounting for the contributions of both electric and magnetic dipole moments induced in particles by external electromagnetic fields is proposed. We show how bianisotropy can lead to the excitation of the trapped mode in metasurfaces. This mode corresponds to the electromagnetic coupling between the out-of-plane particle dipole moments, which do not radiate collectively from the metasurface plane resulting in the enhanced storage of electromagnetic energy. Our approach reveals a physical mechanism of the trapped mode excitation and demonstrates that the specially initiated bianisotropy of particles enables the energy flow between external electromagnetic waves and the trapped mode. Due to this bianisotropy, one can control the process of light-matter interaction and energy storage in all-dielectric metasurfaces via excitation of trapped modes.

Improved Active Interference Canceling Algorithms for Real-Time Protection of 2nd/3rd Level Facilities in Electronic Warfare Environment

In an electronic warfare environment, important equipment or facilities of the friendlies are placed in protective facilities to protect against external Electronic Attacks (EA). No matter how well shielded the facility is, some external electromagnetic waves may penetrate through various paths such as power lines or fans, and the electromagnetic waves may be fatal to certain devices due to the structural resonance of the protective facilities. This paper introduced a real-time electromagnetic canceling technique that removes the resonance field inside the protection facility caused by the intended electronic attack from the enemy. The method makes it possible to cancel the process much faster than the conventional ones that have applied the Matrix Pencil Method (MPM). This is because the internal resonant field can be predicted in a closed-form under the assumption that the external electromagnetic wave is a complex exponential function. Longer exposure to Intended Electromagnetic Interference (IEMI) could be fatal for some devices. Therefore, it is imperative to attenuate the noise within a short time, and a method of reducing internal noise in real-time is beneficial for Electronic Protection (EP). The proposed method could be applied as a new technique to protect important protection facilities, rather than the more traditional method called wrapping using the Faraday cage effect.

Numerical simulation of a coupled system of Maxwell equations and a gas dynamic model

It is known that both linear and nonlinear optical phenomena can be produced when the plasmon in metallic nanostructures are excited by the external electromagnetic waves. In this work, a coupled system of Maxwell equations and a gas dynamic model including a quantum pressure term is employed to simulate the plasmon dynamics of free electron fluid in different metallic nanostructures using a discontinuous Galerkin method. Numerical benchmarks demonstrate that the proposed numerical method can simulate both the high order harmonic generation and the nonlocal effect from metallic nanostructures. Based on the switch-on-and-off investigation, we can conclude that the quantum pressure term in gas dynamics is responsible for the bulk plasmon resonance. In addition, for the dielectric-filled nano-cavity, a coupled effective polarization model is further adopted to investigate the optical behavior of bound electrons. Concerning the numerical setting in this work, a strengthened influence of bound electrons on the generation of high order harmonic waves has been observed.

Self-organized spatially separated silver 3D dendrites as efficient plasmonic nanostructures for surface-enhanced Raman spectroscopy applications

Surface-enhanced Raman spectroscopy (SERS) is a promising optical method for analyzing molecular samples of various nature. Most SERS studies are of an applied nature, indicating a serious potential for their application in analytical practice. Dendritelike nanostructures have great potential for SERS, but the lack of a method for their predictable production significantly limits their implementation. In this paper, a method for controllably obtaining spatially separated, self-organized, and highly-branched silver dendrites via template synthesis in pores of SiO2/Si is proposed. The dendritic branches have nanoscale roughness, creating many plasmon-active “hotspots” required for SERS. The first held 3D modeling of the external electromagnetic wave interaction with such a dendrite, as well as experimental data, confirms this theory. Using the example of a reference biological analyte, which is usually used as a label for other biological molecules, the dendrites’ SERS-sensitivity up to 10−15M was demonstrated with an enhancement factor of 108. The comparison of simulation results with SERS experiments allows distinguishing the presence of electromagnetic and chemical contributions, which have a different effect at various analyte concentrations.

Stabilization of ultrashort pulses by external pumping in an array of carbon nanotubes subject to piezoelectric effects

We study the combined effects of electromagnetic pumping and piezoelectric damping on the propagation of ultrashort pulses in carbon nanotubes. Based on Maxwell’s equations, an effective equation is obtained for the vector potential of the electromagnetic field, which takes into account both the dissipation of the pulse field associated with piezoelectric effects due to the oscillations of the heavy nuclei of the medium and the pumping from an external electromagnetic wave. Our analysis shows that, when the dissipative piezoelectric effects are properly compensated through external pumping, a stable propagation of the ultrashort pulses is achievable. Specifically, we demonstrate the stability of the steady-state form of the electromagnetic pulse at long time scales with variations in various system parameters, including the absorption coefficient of heavy ions as well as the initial pulse field distribution. In addition, the stability of the pulse with respect to angular perturbations—breaking the axisymmetry of the pulse distribution—is substantiated.

Orthonormality of Volkov Solutions and the Sufficient Condition**Supported in part by the National Natural Science Foundation of China under Grants Nos. 11475258, 11205242, and 11675263

We present a simple demonstration on the orthonormality of Volkov solutions with emphasizing on the sufficient condition to the orthonormality. Properly aligning the external electromagnetic wave along the third-axis, the Volkov solutions are eigenfunctions of the hermitian momentum , and the light-cone hamiltonian operators with real eigenvalues, which can lead to a verification of the orthonormality in the context of quantum mechanics when the x3-integration of the external potential is not singularity as severe as δ(0). The hermiticity of the fermion field four-momentum operators validates the application of the demonstration to the intense field quantum electrodynamic. The proof based on a direct calculation to the inner products of the solutions is recapitulated as well in a general manner without dependence on explicit representation of the Dirac matrices and spinors, which can be conducive to understand the sufficient condition and to the study of the polarized electron production where a convenient representation is selected elaborately to project out the spin-polarization.

Electromagnetic Wave Absorbing Materials on Radar Frequency Range

Radar absorbing material (RAM) is a material that which can absorb and reduce energy of electromagnetic wave. Recently, RAMs are widely used as an isolator to protect electromagnetic wave interference (EMI) caused by external electromagnetic field and electromagnetic waves generated by radio frequency (RF) components that disturb the performance of a radio system. Whilest, the most strategic function is as anti-radar coating material to supply the needs of military systems such as aircraft, combat ships and other equipments. Generally, RAM must be resistive, magnetic and dielectric. Absorption at the resonant frequency region is indicated by the permitability and permeability values of the material. The Most literature has reported that the basic material which has the potential to absorb electromagnetic waves is ferrite-based magnetic material, namely barium hexaferrite and strontium hexaferrite. Therefore, the current development of research leads to modification and engineering of the material structure so that it is expected to obtain the right parameters with a maximum absorption rate. Generally, RAMs construction design are grouped on the impedance matching and resonant absorber types.

Excitations of free and localized electrons at nearby energies in reduced cesium tungsten bronze nanocrystals

The low-energy optical absorption mechanism of tungsten oxides and tungsten bronzes is unresolved, with the primary models reported involving free-electron and polaron excitations. Herein, a new mechanism is proposed, based on a systematic and detailed analysis of optical profiles in Cs-doped hexagonal tungsten bronze nanoparticles with varied amounts of oxygen vacancy (VO) and Cs dopant. The Drude–Lorentz analysis of absorption bands, incorporating a newly-developed Mie scattering integration method, has clarified the observed absorption profiles as consisting of three peaks of anisotropic plasmon and polaron exitations. The behavior of the deconvoluted components indicates that VO and Cs+ provide localized and delocalized electrons, respectively, both contributing to the collective plasmon resonance against external electromagnetic waves.

Layered hybrid composites using multi-walled carbon nanotube film as reflection layer and multi-walled carbon nanotubes/neodymium magnet/ epoxy as absorption layer perform selective electromagnetic interference shielding

This work develops a unique layered structural composite to prevent the device from internal electromagnetic (EM) waves’ self-disturbance and external EM wave interference. The composite is composed of two layers, the inner layer is a hybrid composite, using MWCNTs and NdFeB powders as fillers and epoxy as matrix, which is designed as absorbent layer, and the outer is MWCNT-coated non-woven fabric, which is treated as reflection layer. The inner layer containing MWCNTs and magnetic powder of NdFeB can firstly absorb parts of EM waves generating from inside devices, and when the rest EM waves transmit through the inner layer and impinge to the outer layer, almost all of the waves will be reflected back. The reflected waves will go through the inner layer and be absorbed again. In the meanwhile, as the external EM waves impinge to the outer layer, they will be reflected immediately. The optimal combination of this study is able to achieve over 92% (−23.09 dB) absorption and leave least than 8% (−11 dB) reflection of internal EM waves, and over 99.99% reflection of external EM waves.

Analysis of the High-Frequency Response of Thin Wires Irradiated by Electromagnetic Waves Through Tikhonov Regularization Technique

The formula for analyzing the response characteristics of the induced current on a transmission line (TL) excited by high-frequency electromagnetic (EM) waves is a mixed integral-differential equation. The integral part is the Fredholm integral equation of the first kind with serious ill-posedness, which causes difficulty in solving it stably. The regularization technique is a useful method for the analysis of the ill-posed problems. Therefore, in this paper, a method based on the Tikhonov regularization technique is proposed to analyze the high-frequency electromagnetic response of a finite length TL illuminated by external EM waves. The integral operator is discretized by the Simpson formula. The validity and correctness of the proposed method have been verified by numerical examples and the applicability of the proposed method at different errors has been analyzed via the TL with different height.