Microwave Electric Field Research Articles

Conformational Rearrangements of Polyampholytic Polypeptides on Metal Nanoparticle Surface in Microwave Electric Field: Molecular-Dynamics Simulation

Molecular dynamics has been employed to study conformational rearrangements of polyampholytic polypeptides adsorbed on the surface of a metal nanoparticle, with the rearrangements being caused by changes in the direction of particle polarization at a frequency corresponding to microwave electric field. The time dependences of the dipole moments, as well the radial and angular density distributions of adsorbed polypeptide atoms upon the prepolarization of the nanoparticle, have been calculated. The rearrangements occurring in the conformational structure of a polyampholytic polypeptide adsorbed on the nanoparticle upon periodic changes in the particle polarization direction are accompanied by two effects: fluctuations in the conformational structure of the polypeptide and the formation of a ring of macromolecules in the equatorial region of the nanoparticle.

The mechanism of microwave-induced discharge between submillimeter active coke

Microwave-induced active coke discharge has been used in much research related to the environment and energy due to its kinetics and thermal effect. However, the mechanisms of discharge for submillimeter particles are still not clear. This paper presents evidence that the particle shape and gap distance between particles are the possible mechanisms of the microwave discharge. This paper also gives the scope of application of several mechanisms for different particulate materials. Submillimeter particles with about 40–110° tip angle and micron gap distance have the best effect on microwave electric field enhancement. The gap effect is only applicable to materials with a large refractive index, in detail, n > 3 or k > 2 for a 300 μm particle. When the gap distance is too narrow, the electron loss from gap to particle surfaces is large enough, leading to the failure of discharge.

Metamaterial-inspired Fabry–Perot resonator antenna-enhanced spin rectification and inverse spin Hall effects

A 5.8 GHz Fabry–Perot resonator antenna is proposed to improve the performance of the spin rectification effect and inverse spin Hall effect in the far field region. A planar inverse F-shaped antenna and a metamaterial superstrate are used to increase the magnitude of the electromagnetic field. The microwave electric field is enhanced by ∼10-fold, while the magnetic field is enhanced by ∼80-fold. Experimental results prove that the dc signal from the spin rectification effect and inverse spin Hall effect is significantly improved. This letter paves the way for the use of spintronic devices in wireless excitation applications.

Microwave Electric Field Measurement Based on Electromagnetically-Induced Transparency and Absorption in Atomic Vapor Cell at Room Temperature

The traceability of microwave electric field is measured based on the Rydberg atomic quantum interference effect. The rubidium atomic vapor cell at room temperature is used as the probe, and the Autler-Townes splitting of two-photon electromagnetically-induced transparency, three-photon electromagnetically-induced transparency and three-photon electromagnetically-induced absorption effect are analyzed theoretically. The measurement limit of atomic shot noise is also discussed. This method is not only suitable for the traceability and self-calibration measurement of the microwave electric field but also for the sub-wavelength imaging and vector measurement of the microwave electric field and will provide a reference for further miniaturization and integration of the atomic microwave probe.

Theoretical study of the structure and properties of Ni/V porphyrins under microwave electric field: A DFT study

Petroporphyrins with nickel (Ni) and vanadium (V) metals in crude oil are harmful to the catalysts of fluid catalytic cracking (FCC) and residue hydrocracking (RHC) as well as their processes. However, the presence of Ni/V as porphyrins makes them extremely difficult to remove. Recently, microwave method has attracted particular interests for high demetallization efficiency of Ni and V compounds from crude oils. In order to achieve better performance, it is indispensable to understand the theory and mechanism of microwave demetallization. The structure and electronic properties of Ni/V porphyrins were hereby studied via the density functional theory with BLYP functional. External electric fields of different directions and intensities were applied in the simulation. The calculation results demonstrated that the activity of pyrrole ring and –CH3 group can be greatly improved by applying parallel electric field (Ex or E−x), whilst the vertical electric field (Ez or E−z) mainly enhanced the activity of metal atoms. It was also found that the deformation mode of the porphyrin ring changed from dome to saddle style when the vertical electric field was larger than 0.025 a.u, meanwhile, the length of Metal-N bond decreased accordingly. This deformation regularity of the spatial structure innovatively explained the existence of an optimum microwave power in experiments.

Atomic superheterodyne receiver based on microwave-dressed Rydberg spectroscopy

The highly sensitive, phase- and frequency-resolved detection of microwave electric fields is of central importance for diverse fields ranging from astronomy, remote sensing, communication and microwave quantum technology. However, present quantum sensing of microwave electric fields primarily relies on atom-based electrometers only enabling amplitude measurement. Moreover, the best sensitivity of atom-based electrometers is limited by photon shot noise to few $\mu$Vcm$^{-1}$Hz$^{-1/2}$: While going beyond is in principle possible by using squeezed light or Schr\"odinger-cat state, the former is very challenging for atomic experiments while the latter is feasible in all but very small atomic systems. Here we report a novel microwave electric field quantum sensor termed as quantum superhet, which, for the first time, enables experimental measurement of phase and frequency, and makes a sensitivity few tens of nVcm$^{-1}$Hz$^{-1/2}$ readily accessible for current experiments. This sensor is based on microwave-dressed Rydberg atoms and tailored optical spectrum, with very favorable scalings on sensitivity gains. We can experimentally achieve a sensitivity of $55$ nVcm$^{-1}$Hz$^{-1/2}$, with the minimum detectable field being three orders of magnitude smaller than existing quantum electrometers. We also measure phase and frequency, being able to reach a frequency accuracy of few tens of $\mu$Hz for microwave field of just few tens of nVcm$^{-1}$. Our technique can be also applied to sense electric fields at terahertz or radio frequency. This work is a first step towards realizing the long sought-after electromagnetic-wave quantum sensors with quantum projection noise limited sensitivity, promising broad applications such as in radio telescope, terahertz communication and quantum control.

Microwave electrometry via electromagnetically induced absorption in cold Rydberg atoms

The atom-based traceable standard for microwave electrometry shows promising advantages by enabling stable and uniform measurement. Here we theoretically propose and then experimentally realize an alternative direct International System of Units (SI)-traceable and self-calibrated method for measuring a microwave electric field strength based on electromagnetically induced absorption (EIA) in cold Rydberg atoms. Comparing with the method of electromagnetically induced transparency, we show that the equivalence relation between microwave Rabi frequency and Autler-Townes splitting is more valid and is even more robust against the experimental parameters in the EIA's linear region. Furthermore, a narrower linewidth of cold Rydberg EIA enables us to realize a direct SI-traceable microwave-electric-field measurement as small as $\sim$100 $\mu\mathrm{\!V} \mathrm{cm}^{\!-\!1}$.

ДИСПЕРСИОННЫЕ УРАВНЕНИЯ ПОТЕНЦИАЛЬНЫХ КОЛЕБАНИЙ ИОНО-МАГНИТОСФЕРЫ, ПОМЕЩЕННОЙ В ПОСТОЯННОЕ МАГНИТНОЕ И СВЧ-ЭЛЕКТРИЧЕСКОЕ ПОЛЕ

This article provides a theoretical justification for the dispersion equation of the potential vibrations of the ion-magnetosphere. This equation is necessary for solving the urgent scientific and technical problem of developing a probabilistic-statistical method for modeling transport phenomena in a multicomponent, placed microwave electric field.

Enhanced measurement of microwave electric fields with collective Rabi splitting

The collective effects of intracavity Rydberg atoms are investigated and proposed to detect microwave (MW) electric (E) fields with collective Rabi splitting (CRS). When a cavity field drives atoms from ground states to their excited states and a control field further drives them to Rydberg states where a MW field couples Rydberg states, the cavity transmission exhibits a four-peak characteristic, and two side peaks represent the CRS. It is interesting to find that the frequency splitting of CRS changes linearly with the MW-field strength, which can be used to probe MW E-field strength. In the strong coupling regime, the collective effect of Rydberg atoms broadens the CRS peak distance and could improve the detection sensitivity by about 7 times under the given conditions, compared with the common electromagnetically induced transparency scheme. The effects of atomic density and control-field strength on the CRS spectrum are also discussed.

Wavelength transduction from a 3D microwave cavity to telecom using piezoelectric optomechanical crystals.

Microwave-to-optical transduction has received a great deal of interest from the cavity optomechanics community as a landmark application for electro-optomechanical systems. In this Letter, we demonstrate a novel transducer that combines high-frequency mechanical motion and a microwave cavity for the first time. The system consists of a 3D microwave cavity and a gallium arsenide optomechanical crystal, which has been placed in the microwave electric field maximum. This allows the microwave cavity to actuate the gigahertz-frequency mechanical breathing mode in the optomechanical crystal through the piezoelectric effect, which is then read out using a telecom optical mode. The gallium arsenide optomechanical crystal is a good candidate for low-noise microwave-to-telecom transduction, as it has been previously cooled to the mechanical ground state in a dilution refrigerator. Moreover, the 3D microwave cavity architecture can naturally be extended to couple to superconducting qubits and to create hybrid quantum systems.

Repeated exposure to nanosecond high power pulsed microwaves increases cancer incidence in rat.

High-power microwaves are used to inhibit electronics of threatening military or civilian vehicles. This work aims to assess health hazards of high-power microwaves and helps to define hazard threshold levels of modulated radiofrequency exposures such as those emitted by the first generations of mobile phones. Rats were exposed to the highest possible field levels, under single acute or repetitive exposures for eight weeks. Intense microwave electric fields at 1 MV m-1 of nanoseconds duration were applied from two sources at different carrier frequencies of 10 and 3.7 GHz. The repetition rate was 100 pps, and the duration of train pulses lasted from 10 s to twice 8 min. The effects on the central nervous system were evaluated, by labelling brain inflammation marker GFAP and by performing different behavioural tests: rotarod, T-maze, beam-walking, open-field, and avoidance test. Long-time survival was measured in animals repeatedly exposed, and anatomopathological analysis was performed on animals sacrificed at two years of life or earlier in case of precocious death. Control groups were sham exposed. Few effects were observed on behaviour. With acute exposure, an avoidance reflex was shown at very high thermal level (22 W kg-1); GFAP was increased some days after exposure. Most importantly, with repeated exposures, survival time was 4-months shorter in the exposed group, with eleven animals exhibiting a large sub-cutaneous tumour, compared to two in the sham group. A residual X-ray exposure was also present in the beam (0.8 Gy), which is probably not a bias for the observed result. High power microwaves below thermal level in average, can increase cancer prevalence and decrease survival time in rats, without clear effects on behaviour. The parameters of this effect need to be further explored, and a more precise dosimetry to be performed.

Hole Accumulation at the Grain Boundary Enhances Water Oxidation at α-Fe2O3 Electrodes under a Microwave Electric Field

We studied the effects of surface morphology and carrier distribution of α-Fe2O3 electrodes on the enhancement of water electrolysis under microwave (MW) irradiation. We deposited α-Fe2O3 electrodes with various morphologies on Nb-doped rutile TiO2 (100) substrates. α-Fe2O3 films with rough and flat surfaces were deposited using electrodeposition (ED) and pulsed laser deposition (PLD), respectively. The ED α-Fe2O3 film showed a larger response to the MW electric field applied to the electrodes than did the PLD film. In addition, the response was linearly correlated with the MW electric field intensity. Using scanning MW microscopy, we found that the local MW susceptibility of the α-Fe2O3 electrode was enhanced at the grain boundary of the ED α-Fe2O3 film. Analysis of the surface band structure of both ED and PLD α-Fe2O3 films using electrochemical impedance spectroscopy showed that the ED α-Fe2O3 film had a wider depleted layer, indicating increased accumulation of holes on the surface of the electrode to enhance water oxidation. We concluded that the accumulation of holes at the grain boundary of the ED α-Fe2O3 film determines the enhancement of water oxidation under an MW electric field.

Plasma propagation in the microwave window breakdown at the air/dielectric interface

The microwave window breakdown due to the plasma formation greatly limits the power handling capability of high-power microwave systems. However, the experimentally-observed fast plasma propagation cannot be explained using previous theory or simulation results. In this paper, the photoionization is considered to investigate the mechanism of microwave window breakdown at the air/dielectric interface by particle-in-cell simulation. The results show that photoelectrons produced by high-speed photons can profoundly promote discharge above the air/dielectric interface. Then a fast plasma formation and propagation occurs. The speed of plasma propagation can reach 1 × 106 m s−1, which agrees well with experiments. As a result, the transmitting power is attenuated more seriously than the case without the photoionization. Furthermore, the effects of size of microwave window, gas pressure, strength of microwave electric field and distribution of microwave electric field on the plasma propagation are investigated. The results show that the total number of electrons is nonlinearly increasing with the size of microwave window when a uniform microwave electric field is applied. The speed of the plasma propagation exponentially increases with the strength of microwave electric field. Therefore, the photoionization is an indispensable process in the microwave window breakdown with high-strength microwave electric field.

Enhanced microwave electrometry with intracavity anomalous dispersion in Rydberg atoms

Intracavity anomalous dispersion is investigated and proposed to enhance detection sensitivity of weak microwave electric field with Rydberg atoms. When the Rydberg atoms are prepared with Raman gain and the cavity field serves as the probe field driving the metastable-state transition, two cavity modes are amplified due to the gain effect and two gain peaks appear in the cavity transmission, meanwhile, a large anomalous dispersion arises in the gain window. The frequency splitting of two gain peaks shows linear relationship with the MW field strength, which can be used to probe the MW electric-field strength. It is interesting to find that the anomalous dispersion broadens the frequency splitting of two gain peaks dramatically, so the probe sensitivity of MW field could be enhanced by 10 times from simulation, compared with the cavity-less scheme.

Microwave Heating Behavior in SiC Fiber-MO2 Mixtures (M = Ce, Zr)—Selective Heating of Micrometer-Sized Fibers Facilitated by ZrO2 Powder

SiC fiber-MO2 (M = Ce, Zr) mixtures with various compositions were heated by applying an 80 W microwave electric field, to investigate their heating rate, maximum temperature, and dielectric constant. For the SiC fiber-CeO2 mixture, all three parameters continued to increase as the weight ratio of the SiC fiber increased; in contrast, for the SiC fiber-ZrO2 mixture, these parameters reached a maximum value at a certain composition. A thermal gradient of 500 °C was observed at a microlevel in the SiC fiber-ZrO2 mixture, and hot spots were located in regions with a certain composition. This result not only contributes to designing a novel good microwave absorber but also presents new aspects with regard to high-temperature microwave processing, including the mechanism behind the high-temperature gradients on the order of micrometers as well as engineering applications that utilize these high-temperature gradients.

Измерение напряженности электрического поля СВЧ излучения на частоте радиационного перехода между ридберговскими состояниями атомов -=SUP=-85-=/SUP=-Rb

Authors: E.F. Stelmashenko(1), O.A. Klezovich(1), V.N. Baryshev(1), V.A. Tischenko(1), I.Yu. Blinov(1), V.G.Palchikov (1,2(, V. D. Ovsiannikov (1,3) Affiliation: (1)National Research Institute for Physical-Technical and Radiotechnical Measurements, Mendeleevo, Moscow Region , Russia (2)National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, Russia (3)Voronezh State University, University sq.1, 394018, Voronezh, Russia Abstract: Spectral characteristics are determined for the resonance electromagnetically induced transparency (EIT) effect on atomic rubidium vapours, induced by an intense radiation of the wavelength in the region from 479 to 486 nm in presence of a microwave (MW) radiation of a frequency from 1 to 300 GHz, which splits the energy of transition from the 5P3/2 state to a Rydberg state nD5/2 . The magnitude of the EIT peak splitting is proportional to the MW-radiation electric field. Simple approximation equations are derived for evaluating numerically the amplitude of transition between Rydberg nD5/2 and (n+1)P3/2 states with high principal quantum numbers n. An experimental setup is constructed for measuring the MW electric field on the basis of the EIT resonance-splitting measurements in absorption spectra of a probe radiation.

Measurement of the Near Field Distribution of a Microwave Horn Using a Resonant Atomic Probe

We measure the near field distribution of a microwave horn with a resonant atomic probe. The microwave field emitted by a standard microwave horn is investigated utilizing Rydberg electromagnetically inducted transparency (EIT), an all-optical Rydberg detection, in a room temperature caesium vapor cell. The ground 6 S 1 / 2 , excited 6 P 3 / 2 , and Rydberg 56 D 5 / 2 states constitute a three-level system, used as an atomic probe to detect microwave electric fields by analyzing microwave dressed Autler–Townes (AT) splitting. We present a measurement of the electric field distribution of the microwave horn operating at 3.99 GHz in the near field, coupling the transition 56 D 5 / 2 → 57 P 3 / 2 . The microwave dressed AT spectrum reveals information on both the strength and polarization of the field emitted from the microwave horn simultaneously. The measurements are compared with field measurements obtained using a dipole metal probe, and with simulations of the electromagnetic simulated software (EMSS). The atomic probe measurement is in better agreement with the simulations than the metal probe. The deviation from the simulation of measurements taken with the atomic probe is smaller than the metal probe, improving by 1.6 dB. The symmetry of the amplitude distribution of the measured field is studied by comparing the measurements taken on either side of the field maxima.

Dynamical magnetoelectric phenomena of skyrmions in multiferroics

Abstract Magnetic skyrmions, nanoscopic spin vortices carrying a quantized topological number in chiral-lattice magnets, are recently attracting great research interest. Although magnetic skyrmions had been observed only in metallic chiral-lattice magnets such as B20 alloys in the early stage of the research, their realization was discovered in 2012 also in an insulating chiral-lattice magnet Cu 2 OSeO 3 $\textrm{Cu}_2\textrm{OSeO}_3$ . A characteristic of the insulating skyrmions is that they can host multiferroicity, that is, the noncollinear magnetization alignment of skyrmion induces electric polarizations in insulators with a help of the relativistic spin-orbit interaction. It was experimentally confirmed that the skyrmion phase in Cu 2 OSeO 3 $\textrm{Cu}_2\textrm{OSeO}_3$ is indeed accompanied by the spin-induced ferroelectricity. The resulting strong magnetoelectric coupling between magnetizations and electric polarizations can provide us with a means to manipulate and activate magnetic skyrmions by application of electric fields. This is in sharp contrast to skyrmions in metallic systems, which are driven through injection of electric currents. The magnetoelectric phenomena specific to the skyrmion-based multiferroics are attracting intensive research interest, and, in particular, those in dynamical regime are widely recognized as an issue of vital importance because their understanding is crucial both for fundamental science and for technical applications. In this article, we review recent studies on multiferroic properties and dynamical magnetoelectric phenomena of magnetic skyrmions in insulating chiral-lattice magnet Cu 2 OSeO 3 $\textrm{Cu}_2\textrm{OSeO}_3$ . It is argued that the multiferroic skyrmions show unique resonant excitation modes of coupled magnetizations and polarizations, so-called electromagnon excitations, which can be activated both magnetically with a microwave magnetic field and electrically with a microwave electric field. The interference between these two activation processes gives rise to peculiar phenomena in the gigahertz regime. As its representative example, we discuss a recent theoretical prediction of unprecedentedly large nonreciprocal directional dichroism of microwaves in the skyrmion phase of Cu 2 OSeO 3 $\textrm{Cu}_2\textrm{OSeO}_3$ . This phenomenon can be regarded as a one-way window effect on microwaves, that is, the extent of microwave absorption changes significantly when its incident direction is reversed. This dramatic effect was indeed observed by subsequent experiments. These studies demonstrated that the multiferroic skyrmions can be a promising building block for microwave devices.

Scalable microplasma array for argon metastable lasing medium

Optically pumped rare gas laser systems require a lasing medium of high density metastable atoms. A scalable two-dimensional array of quarter-wave resonators produces high microwave electric fields suitable for generating a dense gas of argon 1s5 states. This resonator array is immersed within an evacuated waveguide in order to create a volume of plasma in a relatively wide discharge gap (13 mm) at argon-helium pressures up to 100 Torr using 30 W of continuous microwave power at 2.3 GHz. Spatial density profiles of argon 1s5 states are measured using diode laser absorption spectroscopy with 0.5 mm resolution. The region of argon 1s5 states is mapped in the discharge and shown to have an estimated density in excess of 1×1018m−3 within a volume of 11.6×3.2×0.8mm3.

Tunable nonlinear measurement of microwave electric fields with a dressed-state analysis

A nonlinear absorption spectrum is proposed for measuring microwave electric fields with tunable sensitivity using electromagnetically induced transparency (EIT) in Rydberg atoms. Interacting dark resonances could enhance the nonlinear absorption, which shows a linear relationship with the microwave field (MW) strength. Compared with the linear case, the nonlinear measurement of MW field improves spectrum resolution by about one order of magnitude, the nonlinearity increases the EIT peak values by about two orders of magnitude, moreover the probe sensitivity could be improved by ten times from simulation. It is found that increasing the ratio of two coupling fields can improve probe sensitivity. The maximum probe sensitivity is predicted and explained. The above results can be well understood with the aid of the dressed-state theory.