Electromagnetic Terahertz Research Articles

Internet of Paint (IoP): Channel Modeling and Capacity Analysis for Terahertz Electromagnetic Nanonetworks Embedded in Paint

Internet of Paint (IoP): Channel Modeling and Capacity Analysis for Terahertz Electromagnetic Nanonetworks Embedded in Paint

Highly Sensitive Qualitative and Quantitative Identification of Cashmere and Wool Based on Terahertz Electromagnetically Induced Transparent Metasurface Biosensor.

Cashmere and wool are both natural animal fibers used in the textile industry, but cashmere is of superior quality, is rarer, and more precious. It is therefore important to distinguish the two fibers accurately and effectively. However, challenges due to their similar appearance, morphology, and physical and chemical properties remain. Herein, a terahertz electromagnetic inductive transparency (EIT) metasurface biosensor is introduced for qualitative and quantitative identification of cashmere and wool. The periodic unit structure of the metasurface consists of four rotationally symmetric resonators and two cross-arranged metal secants to form toroidal dipoles and electric dipoles, respectively, so that its effective sensing area can be greatly improved by 1075% compared to the traditional dipole mode, and the sensitivity will be up to 342 GHz/RIU. The amplitude and frequency shift changes of the terahertz transmission spectra caused by the different refractive indices of cashmere/wool can achieve highly sensitive label-free qualitative and quantitative identification of both. The experimental results show that the terahertz metasurface biosensor can work at a concentration of 0.02 mg/mL. It provides a new way to achieve high sensitivity, precision, and trace detection of cashmere/wool, and would be a valuable application for the cashmere industry.

Mathematical Modeling of Resonance Interaction of the Microwave and Terahertz Electromagnetic Radiation with 3D Arrays of Magnetically Functionalized Carbon Nanotubes

Mathematical Modeling of Resonance Interaction of the Microwave and Terahertz Electromagnetic Radiation with 3D Arrays of Magnetically Functionalized Carbon Nanotubes

Terahertz Electromagnetic Shielding and Absorbing of MXenes and Their Composites

Terahertz Electromagnetic Shielding and Absorbing of MXenes and Their Composites

Laser-Induced Graphene/TiCN on a Polyimide/MXene Film as Interference Shielding Materials for Terahertz Electromagnetic Waves

Laser-Induced Graphene/TiCN on a Polyimide/MXene Film as Interference Shielding Materials for Terahertz Electromagnetic Waves

Enhancement of K+ channel permeation by selective terahertz excitation

The optical excitation effects offer an opportunity to gain insights into the structure and the function of K+ channel, contributing to the prediction of possible targets for drug design and precision therapy. Although there has been increasing research attention on the modulation of ion permeation in K+ channel by terahertz electromagnetic (THz-EM) stimuli, little exploration has been conducted regarding the dependence of ion permeation on frequencies. By using two-dimensional (2D) infrared excitation spectrum calculation for the K+ channel, we have discovered that the frequency of 53.60 THz serves as an optimal excitation modulation mode. This mode leads to an almost twofold enhancement in the rate of K+ ion permeation and a tenfold increase in selectivity efficiency. These improvements can be attributed to the coupling mode matching of the excited properties of CO groups in the K+ channel. Our findings propose a promising application of terahertz technology to improve the performance of ion channels, nanomembrane sieves, nanodevices, as well as neural therapy.

Effect of Terahertz Electromagnetic Field on the Permeability of Potassium Channel Kv1.2.

In this paper, the influence of external terahertz electromagnetic fields with different frequencies of 4 THz, 10 THz, 15 THz, and 20 THz on the permeability of the Kv1.2 voltage-gated potassium ion channel on the nerve cell membrane was studied using the combined model of the "Constant Electric Field-Ion Imbalance" method by molecular dynamics. We found that although the applied terahertz electric field does not produce strong resonance with the -C=O groups of the conservative sequence T-V-G-Y-G amino acid residue of the selective filter (SF) of the channel, it would affect the stability of the electrostatic bond between potassium ions and the carbonyl group of T-V-G-Y-G of SF, and it would affect the stability of the hydrogen bond between water molecules and oxygen atoms of the hydroxyl group of the 374THR side chain at the SF entrance, changing the potential and occupied states of ions in the SF and the occurrence probability of the permeation mode of ions and resulting in the change in the permeability of the channel. Compared with no external electric field, when the external electric field with 15 THz frequency is applied, the lifetime of the hydrogen bond is reduced by 29%, the probability of the "soft knock on" mode is decreased by 46.9%, and the ion flux of the channel is activated by 67.7%. Our research results support the view that compared to "direct knock-on", "soft knock-on" is a slower permeation mode.

Polarization-independent analog of electromagnetically induced transparency based on longitudinal and transverse mode coupling

An analog of an electromagnetically induced transparency C4 symmetric device with a silicon array-dielectric layer-Au film F–P cavity is designed. Through the coupling between the waveguide and F–P cavity modes, the polarization-independent terahertz electromagnetic induced transparency (EIT)-like effect is obtained. The coupling analysis between the two types of modes in different orders shows the EIT-like effect, but the orders could affect the EIT-like properties. Moreover, the C4 symmetry structure makes it have polarization-independent characteristics. This research is conducive to obtaining polarization-independent EIT-like devices and to further research on the coupling between different kinds of modes for obtaining EIT-like devices with different performance requirements.

Emission of Terahertz Electromagnetic Waves: A New Spectroscopic Method to Investigate Physical Properties of Solids

Emission of Terahertz Electromagnetic Waves: A New Spectroscopic Method to Investigate Physical Properties of Solids

In-plane symmetry breaking induced tunable spin-dependent responses and polarization states for terahertz wave

Dynamic manipulation of electromagnetic terahertz waves is tremendously desirable to boost the development of favorable functional components of terahertz systems. Reconfigurable chiral metadevices have emerged as promising platforms for active control of spin-dependent responses, however, conventional design principles are restrained by the breakage of out-of-plane symmetries. Here, a type of kirigami-based terahertz metamaterial (MM) is numerically simulated to modulate circular polarization differential transmittance (CPDT) based on the in-plane symmetry breaking. The un-deformed MM empowered with mirror symmetries exhibits indiscriminate propagation for left circular polarization and right circular polarization wave, while the deformed MM with the tensile strain as 24% dramatically facilitates the breakage of in-plane symmetries and retains the CPDT value as high as 0.89. Furtherly, as the tensile strain reaches to 45.5%, the CPDT value is suppressed back to a negligible level and achieves the off-on-off chirality switch function through the continuously stretchable deformation. Moreover, the effect of kirigami cuts, height difference and rotation angle of silicon pillars on the CPDT spectra are also parametrically analyzed. The combination of kirigami technique and terahertz device gives rise to a novel branch of reconfigurable principles, and demonstrates its promising applications of chirality switching, spin-selective manipulation, chiral detection and polarization control.

Amplification of Terahertz Electromagnetic Waves in a Structure with Two Graphene Layers under a Direct Electric Current Flow: a Hydrodynamic Approximation

Amplification of Terahertz Electromagnetic Waves in a Structure with Two Graphene Layers under a Direct Electric Current Flow: a Hydrodynamic Approximation

Improvement of Non-Uniform Temperature Distributions in Intrinsic Josephson Junction Stacks

Terahertz (THz) electromagnetic (EM) wave emitters have been expected for applications because these waves are suitable for non-destructive inspection, telecommunication technologies, and other uses. Strong and coherent THz EM waves are known to radiate from large-sized intrinsic Josephson junction (IJJ) stacks in which the self-heating effect is considerably larger and the temperatures in the mesa are non-uniformly distributed. In this study, we numerically investigate and discuss the temperature and current distributions in large-sized IJJ stacks because these parameters are difficult to analyze through experimental investigation. The temperature and current distributions can be obtained by self-consistently solving the non-linear diffusion equation in an equivalent circuit of the mesa by considering the temperature dependence of several parameters. As shown in the numerical results, self-heating caused the local temperature of the center in the mesa to exceed the critical temperature (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ). To improve the non-uniform temperature and current distributions, we propose an improvement in which an external heat generation system is placed on the edges of the mesa. By applying this measure, the temperature distribution is improved because the edges of the IJJ mesa are heated externally. Furthermore, the local temperatures throughout the mesa were held below Tc, and the current - voltage characteristics were improved using the proposed improvement.

Усиление терагерцовых электромагнитных волн в структуре с двумя слоями графена при протекании постоянного электрического тока: гидродинамическое приближение

The amplification of electromagnetic terahertz radiation in a structure with two layers of hydrodynamic graphene with a direct electric current is studied theoretically. The hydrodynamic conductivity of graphene is investigated. It is shown that the real part of the graphene conductivity can be negative in the terahertz frequency range at the drift velocities of charge carriers in graphene that are lower than the phase velocity of the electromagnetic wave. For small wavevectors of a terahertz wave incident on a graphene structure, the spatial dispersion insignificantly contributes to the hydrodynamic graphene conductivity. Because of this, the amplification efficiency does not depend on the direction of currents in each of the graphene layers. It is shown that graphene with direct electric current can be used to create THz amplifiers operating at room temperature.

Investigation on THz EM Wave Scattering From Oil-Covered Sea Surface: Exploration for an Approach to Probe the Thickness of Oil Film

In this article, a theoretical study is carried out to seek an approach to remotely measure the thickness of the oil film. It is known that it is difficult to probe the oil thickness using a microwave radar due to the fact the dielectric constant of oil is very small compared with seawater for microwave frequencies. While in the range of terahertz (THz) electromagnetic (EM) wave frequency, the dielectric constants of oil and seawater are comparable, resulting in the THz EM fields scattered from the air–oil interface and those from the oil–water interface can produce constructive and destructive interference with the variation in the oil film thickness. Based on this principle, the sensitivity of the THz EM wave to the oil thickness is investigated in this work. First, the oil–seawater two-layer medium is equivalent to a single-layer medium by an equivalent dielectric constant model. Then, the THz EM scattering from the oil-covered sea surface is simulated using the first-order small slope approximation method (SSA-1) and the obtained equivalent dielectric constant. Meanwhile, the influences caused by the damping effect of the oil film, the reduction for friction velocity, and the change in equivalent permittivity on the normalized radar cross section (NRCS) are analyzed. The numerical results show that the NRCSs of THz frequencies are more sensitive to the change in oil thickness than that of microwave frequencies. This property makes the THz EM wave have the potential to probe the thickness of the oil film.

Numerical Study of Voltage-Gated Ca2+ Transport Irradiated by Terahertz Electromagnetic Wave

This paper simulates Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> transmembrane transport through voltage-gated Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> channels in response to terahertz electromagnetic irradiation. The active transport of Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ions is taken into considerations in the Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> transport. Temperature variations due to terahertz electromagnetic loss in physiological medium are simulated. The electromagnetic interaction between terahertz fields and physiological mobile ions at the cellular level is deduced from relativistic electrodynamics. It shows that effects of 0.1 ~ 3 THz electromagnetic fields on cell mobile ions are primarily due to effects of electric fields, and effects of magnetic fields at the cellular level are insignificant. In addition, numerical simulation reveals that terahertz irradiation causes vibration of membrane potential, which is able to activate voltage-gated Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> channels. Besides, bioeffects of terahertz frequency, irradiation duration and electric intensity on the increment of intracellular Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> concentration due to activation of voltage-gated Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> channels are revealed. Meanwhile, numerical results show that temperature rises are inconsequential in the case of different irradiation parameters, indicating the non-thermal bioeffects of voltage-gated Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> transmembrane transport due to terahertz irradiation. Furthermore, the results also reveal that thermal bioeffect can be significant if the irradiation duration is raised long enough for high-dose terahertz irradiation. The numerical simulations lay the basis for understanding the bioeffects of terahertz irradiation on Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> transmembrane transport and pave the way for further exploration in modulation of intracellular Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> concentration with terahertz electromagnetic wave.

Transition to a Superpermeation Phase of Confined Water Induced by a Terahertz Electromagnetic Wave.

Excellent permeation of one-dimensional (1-D) confined water across membrane channels is implicated in physiological processes and widely inspires the design of novel nanodevices and materials. Here, through molecular dynamics simulations, we proposed a phase transition to superpermeation (approximately 1 order of magnitude enhancement) of confined water across a 1-D water channel caused by a terahertz electromagnetic stimulus with a limited thermal effect. The underlying mechanism is revealed to be a combination of strength matching and frequency resonance between a relatively weak stimulus and the hydrogen bond network of 1-D confined water, rather than the bulk water outside. This combination causes an anomalously structural phase transition of only the confined water while efficiently limiting the thermal effect of bulk water. Our findings are promising for promoting the developments of advanced nanofluidic systems and terahertz technology and even physiological research.

Terahertz high-resolution wideband focusing metasurface based on catenary structure

Due to several excellent properties, electromagnetic terahertz waves may be very useful for imaging applications, provided sufficiently high-resolution can be achieved. A tightly focused beam can be produced using a two-dimensional metasurface and catenary structure that enables phase-tuning of electromagnetic waves. We modified the catenary structure to produce a metasurface and a non-diffracting 0th-order Bessel beam. According to our calculation, the formed wideband focal spots can be smaller than Abbe’s diffraction limit, between 350 GHz and 450 GHz, with a maximum gain of 15.1 dB. Such a metasurface could open new doors for future high-resolution medical imaging research and technology.

Excitation of terahertz radiation by parametric mixing of four waves in magnetized plasma

THz radiation may be excited by nonlinear mixing of two counter-propagating laser beams, having frequency difference ω1∼ω2≥2ωp, in under dense plasma. Beating laser beams exert nonlinear ponderomotive force on plasma electrons and excite a nonlinear density perturbation. The nonlinear density perturbation drives a non-resonant space charge mode which may excite a pair of plasma wave and back scattered electromagnetic terahertz wave at resonance. The presence of transverse magnetic field further enhances the growth of THz wave. The transverse magnetic field also tunes the amplitude and frequency of THz wave. The maximum growth rate of excitation process Γ∼6.22×10−6 s−1 is achieved for applied magnetic field ∼175 kG.

Emission of Terahertz Electromagnetic Waves by Femtosecond Laser Pulse Irradiation in Solids and Its Application to Materials Science

Emission of Terahertz Electromagnetic Waves by Femtosecond Laser Pulse Irradiation in Solids and Its Application to Materials Science

Stimulated Brillouin scattering of terahertz electromagnetic pulses in paraelectrics

The nonlinear acoustoelectromagnetic phenomena in the terahertz (THz) range in the crystalline paraelectric SrTiO3 are investigated theoretically. The goal is to investigate an appearance of short THz electromagnetic (EM) pulses. The moderate cooling to the temperature T ≈ 77 K is considered. The resonant three-wave interaction of two counterpropagating EM THz waves with the longitudinal acoustic wave of the difference frequency is under investigation that is called the stimulated Brillouin scattering. This resonant interaction is due to the quadratic nonlinearity called electrostriction. The appearance of short EM pulses is possible when the input amplitudes of the signal EM wave are comparable with the pump amplitude and the duration of the input pulses is quite long. In the temporal scale associated with the EM wave propagation within a crystal, the cubic EM nonlinearity and the EM wave dispersion affect this three-wave resonant interaction. Under the development of the resonant nonlinear interaction, the modulation instability occurs that results in the complex and even chaotic wave modulation.