Frequency Of External Electric Field Research Articles

Lead indium niobate-lead magnesium niobate-lead titanate based whispering gallery mode resonator

Whispering gallery mode resonators (WGMRs) have garnered significant interest due to their potential applications in the fields of electro-optic modulation and microwave to optical photon conversion. In this study, we have leveraged an electro-optic crystal, lead indium niobate-lead magnesium niobate-lead titanate (PIN-PMN-PT), to fabricate a high-quality WGMR. Our investigation revealed that the crystal composition used in this work is 0.24PIN-0.45PMN-0.31PT, and each element of the whole sample is homogeneously distributed. The dielectric properties of the sample revealed the necessity of limiting the temperature and external electric field frequency to below 100 °C and 106 Hz, respectively. The obtained optical quality factor value (Q value) of the resonator is ∼0.7 × 105. Impressively, our resonator could be conveniently tuned by exploiting the enormous inverse piezoelectric effect d31 of the crystal, thereby alleviating the need for precise fabrication. Furthermore, a theoretical analysis of our resonator revealed that a calculated resonance wavelength shift is within a broad range of 2.16 nm. Intriguingly, if the surface roughness of the resonator is reduced tenfold, we can increase the calculated Q value dependent on surface scattering by 104. Our finding showcases the tremendous potential of the PIN-PMN-PT crystal-based WGMR as versatile building blocks for a variety of applications in the burgeoning field of photonic technology.

Analysis of the temperature-frequency effect on dielectric losses in a grain medium

The aim of the study is to determine the influence of the thermal effect on dielectric losses in grain mass subject to bruising during drying and storage on the example of wheat across a wide external electric field frequency range. The study of the electrophysical characteristics of a dispersed medium comprising mechanically activated wheat grains takes into account the effect of the degree of breakage on the dielectric parameters of the studied medium. The studies were carried out on experimental samples having different degrees of mechanical activation of particles, which ranged in size from from 50 to 1000 μm. Variations in the dielectric loss tangent were studied using the dielectric method across a wide temperature-frequency range. Studies of variations in dielectric properties were carried out for wheat sam-ples subjected to grinding according to the mechanical activation method at temperatures varying from 20°C to 255°C with a constant heating rate of 0.7 deg / min. During the course of the experiment, the frequency of the external electric field was varied from 25 Hz to 1∙106 Hz. Dielectric constant and dielectric loss tangent calculations were carried out using data on electrical capacity and conductivity obtained using an E7-20 immittance meter and a measuring cell in the form of a flat capacitor. An analysis of variations in these dielectric characteristics was also performed. The obtained stable correlation of the dielectric loss tangent with the frequency of external electric impact and the degree of heating of the samples was most pronounced for finely dispersed samples (particle size 50 μm). Variations in dielectric characteristics are most significant when the frequency decreases to 100 Hz and below. The study of variations in the main dielectric parameters can be used to prevent self-heating and ignition of the grain mass during storage, as well as for selecting the most efficient energy-saving drying mode.

Dielectric losses under heat treatment of dispersed media

The purpose of the paper is to study the dependence of dielectric losses of mechanically activated grain crops on example of wheat under heat treatment on temperature and external electric field frequency as well as to examine the effect of particle size of fine grain samples on grain electrophysical characteristics and dielectric losses. Experimental samples of dispersed systems with particle sizes in the range from 50 to 1000 μm are prepared by the method of mechanical activation. The temperature dependence of the dielectric loss angle tangent is measured using the dielectric method over a wide frequency range. The dependence of the dielectric loss angle tangent tgδ of mechanically activated wheat samples with the different degrees of particle dispersion in a wide temperature range from 20°C to 250°C with a heating rate of 0.7 deg/min is studied. It is found out that the external electric field frequency varies in the range from 25 Hz to 106 Hz. Electric capacitance and conductivity are measured using an E7-20 immitance meter and a specially designed measuring cell. Dielectric characteristics are calculated. Experimental data are presented in the form of graphs and diagrams. We have determined the correlation of the tangent of the dielectric loss angle tgδ with the frequency of the external electric field and temperature, which is most characteristic for fine samples. The most finely dispersed samples with a particle size of less than 50 microns are shown to have high electrical activity. Increase in the dielectric permittivity and the tangent of the dielectric loss angle is most noticeable at the frequencies below 100 Hz. The study of dielectric characteristics allows to choose an effective energy-saving drying mode of the crop under study.

Frequency dependence of electric field tunability in a photonic liquid crystal fiber based on gold nanoparticles-doped 6CHBT nematic liquid crystal

In this paper, we investigate an external electric field frequency influence on a photonic liquid crystal fiber (PLCF) based on a gold nanoparticles (NPs)-doped nematic liquid crystal (LC) and its response to the external electric field. We used a 6CHBT nematic LC doped with 2-nm gold NPs in a weight concentration of 0.1%, 0.2%, 0.3%, and 0.5%. Full Text: PDF ReferencesJ. C. Knight, T. A. Birks, P. St. J. Russell, and D. M. Atkin, "All-silica single-mode optical fiber with photonic crystal cladding," Opt. Lett. 21, 1547-1549 (1996) CrossRef J. C. Knight,T. A. Birks, P. S. J.Russell, , and J. P. De Sandro, "Properties of photonic crystal fiber and the effective index model", JOSA A, 15(3), 748-752, (1998) CrossRef S. A. Cerqueira,F. Luan, C. M. B. Cordeiro, A. K. George, and J. C. Knight, "Hybrid photonic crystal fiber", "Optics Express", 14(2), 926-931,(2006) CrossRef W. Bragg, "Liquid Crystals", Nature 133, 445-456, (1934) https://doi.org/10.1038/133445a0 CrossRef J. Kędzierski, K. Garbat, Z. Raszewski, M. Kojdecki, K. Kowiorski, L. Jaroszewicz, and W. Piecek, "Optical properties of a liquid crystal with small ordinary and extraordinary refractive indices and small optical anisotropy", Opto-Electronics Review, 22(3), 162-165, (2014) CrossRef Y. Li, and S. T. Wu, "Polarization independent adaptive microlens with a blue-phase liquid crystal", Optics express, 19(9), 8045-8050, (2011) CrossRef T. Woliński, S. Ertman, K. Rutkowska, D. Budaszewski, M. Sala-Tefelska, M. Chychłowski, K. Orzechowski, K. Bednarska, P. Lesiak, "Photonic Liquid Crystal Fibers - 15 years of research activities at Warsaw University of Technology", Phot. Lett. Pol., (11), (2), 22-24, (2019) https://doi.org/10.4302/plp.v11i2.907. CrossRef T.T. Larsen, A. Bjraklev, D.S. Hermann, J. Broeng, Opt. Expr. 11(20), 2589, (2003) CrossRef T.R. Woliński, K. Szaniawska, K. Bondarczuk, P. Lesiak, A.W. Domański, R. Dąbrowski, E. Nowinowski-Kruszelnicki, J. Wójcik, "Propagation properties of photonic crystal fibers filled with nematic liquid crystals", Opto-Electron. Rev. 13(2), 59 (2005) DirectLink L. Scolari, S. Gauza, H. Xianyu, L. Zhai, L. Eskildsen, T. T. Alkeskjold, S.-T. Wu, and A. Bjarklev, "Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals," Opt. Express 17(5), 3754-3764 (2009). CrossRef A. Siarkowska, M. Chychłowski, D. Budaszewski, B. Jankiewicz, B. Bartosewicz, and T. R. Woliński, "Thermo-and electro-optical properties of photonic liquid crystal fibers doped with gold nanoparticles", Beilstein Journal of Nanotechnology, 8(1), 2790-2801, (2017) CrossRef D. Budaszewski, M. Chychłowski, A. Budaszewska, B. Bartosewicz, B. Jankiewicz, and T. R. Woliński, "Enhanced efficiency of electric field tunability in photonic liquid crystal fibers doped with gold nanoparticles", Optics express, 27(10), 14260-14269, (2019) CrossRef D. Budaszewski, A. Siarkowska, M. Chychłowski, B. Jankiewicz, B. Bartosewicz, R. Dąbrowski, T. R. Woliński, "Nanoparticles-enhanced photonic liquid crystal fibers", Journal of Molecular Liquids, 267, 271-278, (2018) CrossRef

Stability of two layers dielectric-electrolyte microflow subjected to an alternating external electric field.

The stability of the electroosmotic flow of the two-phase system electrolyte-dielectric with a free interface in the microchannel under an external electric field is examined theoretically. The mathematical model includes the Nernst-Plank equations for the ion concentrations. The linear stability of the 1D nonstationary solution with respect to the small, periodic perturbations along the channel, is studied. Two types of instability have been highlighted. The first is known as the long-wave instability and is connected with the distortion of the free charge on the interface. In the long-wave area, the results are in good agreement with the ones obtained theoretically and experimentally in the literature. The second type of instability is a short-wave and mostly connected with the disturbance of the electrolyte conductivity. The short-wave type of instability has not been found previously in the literature and constitutes the basis and the strength of the present work. It is revealed that with the increase of the external electric field frequency, the 1D flow is stabilized. The dependence of the flow on the other parameters of the system is qualitatively the same as for the constant electric field.

Calculating the High-Frequency Electrical Conductivity of a Thin Metallic Layer for an Ellipsoidal Fermi Surface

The conductivity of a thin metallic layer in an ac electric field is calculated with respect to different specular reflection coefficients of the layer surfaces for an ellipsoidal Fermi surface. The ratio between the free path of electron conduction and layer thickness is not limited. The dependences of the absolute value and the argument of dimensionless conductivity on the dimensionless layer’s thickness, dimensionless external electric field frequency, and specular reflection coefficient of one of the layer surfaces at different ellipticity parameters of the Fermi surface are analyzed.

Nonlinear Schrödinger equation and classical-field description of thermal radiation

I show that Lamb-Retherford experiment can be fully described within the framework of classical field theory without using concepts such as the discrete states of the atom and jump-like electron transitions between them. The rate of stimulated decay of the metastable state of a hydrogen atom in an external periodic electric field is determined. The dependence of this rate on the frequency and amplitude of the external electric field, as well as on the parameters of the atom, has been obtained. It is shown that the maximum value of the stimulated decay rate of the metastable state of a hydrogen atom is achieved at an external electric field frequency equal to the frequency shift corresponding to either the fine structure of the hydrogen atom or the Lamb shift.

The influence of low frequency of external electric field on nucleation enhancement of hen egg-white lysozyme (HEWL)

Protein crystal nucleation processes are drawing increasing interests in both academic and industrial communities. Electric field is a promising means, due to its versatility and easy application, among various external fields that may lead to controllable desired protein crystal nucleation. Different from literature reported experimental and theoretical studies that examined the effects of high frequency electric fields; this work was focused on the low frequency range. For this purpose, Hen-White Lysozyme crystal nucleation from its aqueous solution was used as the model system. We found by experiments that the nucleation rate is non-monotonously dependent on electric field frequency less than 1kHz, which may be ascribed to the mutual orientation modification between neighbor protein molecules induced by the external low frequency, and is different from the case of high frequencies that influence the intermolecular interactions.

Structural, AC conductivity, dielectric behavior and magnetic properties of Mg-substituted LiFe5O8 powders synthesized by sol–gel auto-combustion method

Magnesium-substituted lithium ferrite powders (Li1−xMg2xFe5−xO8 where x = 0.0–0.8) were prepared by sol–gel auto-combustion method. XRD profiles revealed that all compositions were single cubic ferrite structure for the precursors annealed at 800 °C for 2 h. The crystallite size was found to decrease whereas the lattice parameter was increased with increasing Mg2+ ion content. The microstructure of the formed powders was Mg concentration dependent. Increasing the Mg2+ ion ratio was found to inhibit the grain growth of the formed ferrite. The AC electrical conductivity of Mg2+ ion substituted lithium ferrite samples was raised with increasing the concentration of Mg2+ ions as the result of increasing the hopping of electrons between Fe2+ and Fe3+ ions. Meanwhile, dielectric constant (e′) was diminished with increasing the frequency of external electric field as well as increasing the temperature and concentration of Mg2+ ions. Alongside, the formed crystalline magnesium substituted lithium ferrite had good magnetic properties. High saturation magnetization (78.7 emu/g) was attained by the formed ferrite sample at Mg2+ molar ratio of 0.4 annealed at 800 °C for 2 h.

Optical characteristics of frequency-driven 128 × 128 elements nematic liquid crystal cylindrical lens array based on equivalent circuit theory

In this paper, we propose a novel approach for realising a nematic liquid crystal 128 × 128 elements cylindrical lens array. This liquid crystal-cylindrical lens array is realised with an element clear aperture of 200 μm × 60 μm. In addition, its electro-optical feature is tuneable via the change of external electric field frequency. Based on the equivalent circuit theory proposed, the electro-optical features of the proposed liquid crystal-cylindrical lens array are analysed from the electric perspective. Experiments have been conducted to confirm the validity of the proposed algorithm. According to the experimental result, the liquid crystal device is able to focus collimated light in the range of 20–600 μm when the frequency of the applied voltage ranges from 100 Hz to 100 KHz. Thus, the effect of frequency-driving focusing is similar to that of applied voltage-driving focusing, which suggests a new way for liquid crystal device driving. Besides, power consumption of liquid crystal devices can also be reduced with the proposed method.

Analytical Solutions of Time Periodic Electroosmotic Flow in a Semicircular Microchannel

The time periodic electroosmotic flow of Newtonian fluids through a semicircular microchannel is studied under the Debye–Hückel approximation. Analytical series of solutions are found, and they consist of a time-dependent oscillating part and a time-dependent generating or transient part. Some new physical phenomena are found. The electroosmotic flow driven by an alternating electric field is not periodic in time, but quasi-periodic. There is a phase shift between voltage and flow, which is only dependent on the frequency of external electric field.

Cluster Structure of Salt Solutions in Polar Dielectric Liquids

The aim of the study is to demonstrate that separation of solvated ions in solution of mixed salts under the action of external periodic electric field is caused by the formation of clusters consisting of solvent molecules and surrounding the ions. Such clusters have the dimensions of about 0.1 µm. The study includes the theoretical estimation of cluster dimensions and experimental determination of the external electric field frequency that gives rise to the separation of solvated ions. The results testify that placing the volume distributed electric charge of ion into dielectric liquid is accompanied by the formation of supramolecular particles. We called such particles “clusters”. The linear dimensions of clusters significantly exceed the first and the second radii of solvation (approximately 1 Angstrom) and amount to nearly 0.1 µm. At such sizes, inertial properties of clusters and their natural frequencies may allow controlling their movement by applying an external electric field to solution.

Clusters Formation in Salts Solution in Polar Dielectric Liquids and Electrically-induced Separation of Solvated Ions

The aim of study is to demonstrate that separation of solvated ions in solution of mix of salts under the action of external periodic electric field happens because of around ions there are formed clusters consisting of molecules of solvent and the sizes of such clusters have dimensions ~ 0.1 μm. In investigations the sizes of clusters theoretically were defined and experimentally value of frequency of external electric field which action excites the effect of separation of the solvated ions was defined. Experiments were done in the Technical Physics Chair of the National Research Tomsk Polytechnic University. At theoretical determination of the dimensions of clusters Poisson's equation was solved and was considered that polar molecules of solvent are oriented under the action of electric field of an ion. The chemical composition of samples of solutions was determined by means of the X-ray excited fluorescent radiation analysis method. Theoretical estimates and results of experiments confirmed the assumption that clusters which are formed around ions in solutions have the dimensions ~ 0.1 μm. Results of investigation testify that placing of volume distributed electric charge of ion in Original Research Article British Journal of Applied Science & Technology, 4(18): 2014 2539 dielectric liquid is accompanied by formation of the supramolecular particles, which we called “clusters”, linear sizes of which is significantly more than first and second radiuses of solvation (~ 1 Angstrom) and reach size ~ 0.1 μm. At such sizes inertial properties of clusters and their natural frequencies give the chance to operate their movement by means of action of external electric field on solution.

Influence of alternating current electric field on the photocatalytic activity of Mo6+-doped and Ag0-loaded nano-TiO2

Influence of external applied electric field on the photocatalytic activity of Mo6+-doped and Ag0-loaded nano-TiO2 (Mo6+/Ag0/TiO2) was studied by the degradation of methyl orange (MO). The degradation rate of MO by direct current (DC) electric field could be enhanced to some extent but not proportional to voltage, while the degradation rate of MO by alternating current (AC) electric field was obviously improved along with the increase of frequency. This shows not only the voltage but also the frequency of external electric field affect the photocatalytic activity of the composite catalyst. From the theories of semiconductor and quantum mechanics, the mechanism for AC electric field to promote the degradation of organic pollutant was discussed.

Synchronized Fabry-Perot cavity used for enhanced sensitivity electro-optic measurements of electric fields in the microwave range.

An electro-optic (EO) sensing system for measuring free-space electric fields in the microwave range has been developed. The system is based on a phase modulation heterodyning technique using a Mach-Zehnder interferometer. In one of the arms of the interferometer, an acousto-optic frequency shifter is used to downconvert the frequency of the detected signal in order to discriminate it from parasites emitted at the external electric field frequency. The sensing part is a LiTaO3 crystal placed in a Fabry-Perot cavity. The cavity aims at enhancing the sensitivity of the measurements. Cavity-based EO setups already used in the literature propose this sensitivity enhancement at the expense of the frequency bandwidth, whereas our setup allows this without a major impact on the frequency bandwidth. Electric fields are measured at both 15 kHz and 2.4 GHz with cavities of two different finesses; the best EO phase retardation gains obtained with the cavity are 34 and 60, respectively. The minimum detectable electric field is 0.003 V⋅m-1⋅Hz-1/2.

Quadratic electro-optic effect in GaN-based materials

The mechanism and influence of quadratic electro-optic effect in GaN-based materials is investigated. It is found that the peaks appearing in the measured electro-optic signal strongly depend on the modulation frequency of external electric field, which is attributed to the vibration frequency resonance effect. The intrinsic vibration frequency of the investigated samples is estimated to be around 21.95 kHz and is assigned to be the base frequency of the resonance.

Structural analysis, magnetic and electrical properties of samarium substituted lithium–nickel mixed ferrites

A series of Sm-doped Li–Ni ferrites with formula of (Li0.5Fe0.5)0.4Ni0.6SmyFe2−yO4, where 0.0≤y≤0.1 were prepared by double sintering ceramic technique. The structure was characterized by X-ray diffraction, which has confirmed the formation of single-phase spinel structure. The samarium concentration dependence of lattice parameters obeys Vegard's law. The octahedral site radii increased with Sm content while the tetrahedral site radii decreased. Deviation from the ideal crystal structure (Δ) is found to decrease with Sm substitution, and the hopping length on the octahedral site is found to increase with Sm content. Hall measurement confirmed p-type conductivity behavior for Sm-doped ferrite and the main charge transport mechanism is hopping of halls between Ni2+ and Ni3+. Sintering at 1300°C resulted in low resistivity ferrite, which was found to increase with Sm content. Resistivity is governed by both charge carrier mobility and carrier concentration. It decreases with frequency, and this behavior with frequency is discussed according to Koop's theorem. The dielectric constant is found to decrease more rapidly at low frequencies than at higher frequencies while the dielectric constant increases with Sm content. The decrease in ε″ with frequency agrees with Deby's type relaxation process. Maximum in ε″ is observed when the hopping frequency is equal to the external electric field frequency. The variation in tanδ with frequency shows a similar nature to that of ε″ with frequency. The magnetization under applied magnetic field for the samples exhibits a clear hysteretic behavior. The scanning electron microscope (SEM) studies showed that the domain walls may tend to be trapped (pinned) by non-magnetic inclusions, precipitates and voids. The saturation magnetization (MS) increases with the sintering temperature, while the coercivity (HCi) is found to decrease.

Dielectric properties of Ba(Ti 1 − xSn x)O 3 ceramics in the paraelectric phase

The outcomes of dilatometric, rentgenographic (XRD), microscopic (SEM) as well as dielectric measurements of polycrystalline Ba(Ti 1 − x Sn x )O 3 (BTS x) are described. These measurements were carried out within the range of para-ferroelectric phase transition and also for the high temperature paraelectric phase (from 300 K to 723 K). Within the range, where glass-like anomalies were noticed, the occurrences of electric properties peaks were recorded as well. Their occurrences are interpreted under the assumption of polar regions presence within the paraelectric phase. The size and dynamics of these polar regions influence the dielectric response at given temperatures and frequency of external electric field. Anomalies of dielectric losses and phase angle are pointing out on non-homogeneity and thermal evolution of polar regions.

Resonant acoustic spectroscopy of the interaction of the single-mode high-power laser radiation with crystals

Resonant acoustic spectroscopy technique gives the opportunity to measure the crystal temperature during linear and nonlinear interaction of the laser radiation with crystals. It is based on the registration of the crystal piezoelectric or acoustical resonance frequency change caused by the interaction of the laser radiation with crystals. Piezoelectric resonance is observed by measuring the dependence of the sample electrical impedance on the external electric field frequency. It is shown that inhomogeneous crystal heating can be characterized by the equivalent crystal temperature depending on the influence laser power. Equivalent crystal temperature can be directly determined from the measured piezoelectric resonance frequency.

The self-consistent determination of HF electroconductivity of strongly coupled plasmas

Here is presented the calculation of the dynamic electrical conductivity of fully ionized, strongly coupled plasmas as a function of the external electric field frequency ω. The calculations are based on the formula for the energy-dependent collision frequency which is determined by means of the Green function theory methods, as a sum over the Matsubara frequencies. The domain of extremely high electron density: 10 21 ⩽ n e ⩽ 10 24 cm − 3 , and for the temperature varying from 10 kK to 1000 kK was examined. The real and imaginary parts of the conductivity for every electron density are presented in the generalized Drude-like form as a two-parameter function of the frequency ω in the region 0 < ω < 0.5 ω p , where ω p is the plasma frequency. A good agreement between the obtained results and the existing theoretical and computing simulation data is shown.