Electric Field Amplitude Research Articles

A low speckle laser pico-projector using dynamic light scattering liquid crystal devices

A dynamic light scattering liquid crystal (DLS-LC) device is applied to reduce speckle from a laser pico-projector. The DLS-LC device produces time-varying scattering patterns, which can decrease the degree of spatial and temporal coherence of the laser and achieve a very effective reduction in the speckle. The influence of the amplitude and frequency of the applied electric field for the DLS-LC device on the light scattering characteristics and speckle contrast are studied. The speckle contrast is reduced by as much as 62% with a low electric field amplitude (4.2 V/μm).

A molecular dynamics study of thermal behavior of ammonia/Cu nanorefrigerant flow under different initial pressures and electric fields

In today’s world, energy consumption was increased dramatically. This increase in consumption has led to many advances in heat transfer (HT) and phase change (PC) in mechanicalprocesses. This study investigates the thermal conductivity (TC) and PC of Cu-Ammonia nano-refrigerant (NR). This study uses the molecular dynamics (MD) method in an aluminium nanochannel (NC). This simulation examines the effect of external electric field amplitude (EFA) and the initial pressure (IP) on atomic (temperature (T) and density (D) profiles) and thermal properties (TP) of the NR. The kinetic energy (KE) and total energy (TE) are examined to appraise the stability process. The results show that increasing the IP to 5 bar increases the maximum density value to 0.03 atoms/Å3, which indicates an improvement in the sample's atomic properties (AP). The PC particle rate increases with increasing IP from 53 to 59%. Also, increasing the IP decreases PC duration (from 2.96 to 2.89 ns) and increases the TC (0.76 to 0.80 W/m K). On the other hand, by investigating the increase in the applied EFA to the NR from 1 to 5 Å, the maximum density increases from 0.028 to 0.029 atoms/Å3, and the rate of PC particles decreases to 49%. Also, an increase in the EFA causes an increase in the PC duration and a reduction in TC in the sample.

Parametric studies of stream instability-induced higher harmonics in plasma ionization breakdown near an emissive dielectric surface

In this work, we comprehensively investigate the generation of higher harmonic (HH) electric fields normal to the applied rf electric field in multipactor-coexisting plasma breakdown by fully kinetic particle-in-cell (PIC) simulations and a theoretical model. Firstly, a base case at driving frequency 1 GHz, transverse rf electric field amplitude 3 MV m−1, and background gas pressure 0.2 Torr, is studied in detail. The enhanced harmonic frequency observed is around ten times the fundamental rf frequency, significantly lower than the Langmuir frequency. A theoretical model reveals that the fundamental mechanism of HHs generation is stream–plasma instability, which originates from stream-like secondary electron emission interacting with plasma. The resulting HH frequency and the growth rate of its oscillating amplitude from the theoretical model, agree well with the PIC simulations. With increasing pressure, the HH oscillations are found to be significantly reduced. This is because at higher pressure the gas ionization rate is higher, which causes a more rapidly increasing plasma density, leaving less time for the growth of instability. Furthermore, the parameter space in terms of background gas pressure and rf field amplitude within which the HHs appear is revealed. Finally, the effect of the driving rf frequency on HHs is also investigated, and it is found that the instability-induced oscillating HHs field remains when the driving frequency is increased to 2 GHz, however, it is highly reduced at higher driving frequency of 5 GHz, as oscillations at the fundamental frequency start playing a more important role.

Formation and interaction of multi-dimensional electrostatic ion-acoustic solitons in two-electron temperature plasmas

Ion-acoustic waves are investigated in an unmagnetized collisionless plasma comprising dynamical ions and inertialess cold and hot (C–H) electrons expressed by Maxwellian, kappa, and (r, q) distributions. The reductive perturbation theory is applied for deriving a modified Kadomtsev–Petviashvili (mKP) equation to examine the characteristics of ion-acoustic structures (solitary waves, IASWs). The Hirota bilinear formalism is used to investigate the propagation of a single soliton and the interaction of two solitons with special reference to space plasmas. It is found that ratio of number density of cold to hot electrons and non-Maxwellian nature of cold electrons not only affect the propagation characteristics of single mKP solitons but also alter the interaction time of the IASWs. It is found that the swiftness of the interaction of solitons for flat-topped distribution surpasses both kappa and Maxwellian distributions. It is also found that the bipolar and tripolar structures depend on the ratio of the propagation vectors. The ranges of electric field amplitude for the IASWs are calculated for C–H electron distributions corresponding to Saturn's B-ring and the region just beyond terrestrial magnetopause, and are shown to agree with Cassini wideband receiver observational data and wideband plasma wave instrument's waveform data.

Controlling the polarization and phase of high-order harmonics with a plasmonic metasurface

Nanostructured surfaces, or metasurfaces, allow exquisite control of linear and nonlinear optical processes by reshaping the amplitude, phase, and polarization of electric and magnetic fields near wavelength-scale heterogeneities. Recently, metasurfaces have broken new ground in high-field attosecond science where they have been utilized to amplify the emission of high-order harmonics of femtosecond infrared laser pulses, a notoriously inefficient process, by enhancing the incident field, and to shape the emitted high harmonics in space. Here we show control of the polarization and phase of high harmonics with a plasmonic metasurface. We design and fabricate perpendicularly aligned rectangular gold antennas on a silicon crystal that generate circularly polarized deep-ultraviolet high harmonics, from a circularly polarized infrared driver, providing a simple path for achieving circular emission from patterned crystals. Our metasurface enhances the circularly polarized harmonics up to ∼ 43 times when compared to the unpatterned surface, where harmonics are quenched. Looking forward, circularly polarized high harmonics will be useful tools for sensing chiral laser–matter interactions and magnetic materials. Our approach paves the way for polarization control at even shorter, extreme ultraviolet, wavelengths.

Molecular dynamics study of the effect of external electric field amplitude and cavity on thermal properties of Ammonia/Copper Nano-Refrigerant

With the ever-increasing energy costs, the need to improve the efficiency of cooling systems, reduce costs, and optimize the design is usually the first goal for system designers. One way to improve these systems is to use nano-refrigerants (NRs). This study simulates the thermal manner of ammonia refrigerant with Cu nanoparticles (NPs) in a nanochannel (NC) by calculating parameters such as velocity (V) and temperature (T) profiles, aggregation time (AT), and heat flux (HF). The result shows that by increasing the electric field amplitude (EFA) from 1 to 5 V/m, the maximum V and maximum T increase from 0.00086 Å/ps and 240 K to 0.00089 Å/ps and 245 K, respectively. With increasing the external EFA to 5 V/m, the HF value converges to 1395 W/m2, and the AT decreases to 3.90 ns. On the other hand, the change in maximum V in the samples with the pyramid, half-spherical (HS), and rectangular cubic (RC) cavities reached 0.74000 Å/ps, 0.00072 Å/ps, and 0.6565 Å/ps, respectively, and the maximum T changes to 232 K, 238 K, and 235 K in the RC, HS, and pyramid cavities samples. The results show that the structure has a higher HF in the presence of the RC cavity. So, the HF and AT values for samples with RC cavities are 1650 W/m2 and 4.59 ns, respectively.

Printed Polymer‐Stabilized Chiral Nematic Liquid Crystal Privacy Windows

AbstractIn this paper, drop‐on‐demand (DoD) printing is demonstrated of polymer stabilized chiral nematic liquid crystal (PSCLC) privacy windows that can function in either a conventional mode (scattering to transparent) or reverse mode (transparent to scattering) with the application of an electric field. Inkjet printed droplets of the PSCLC mixture, with diameters of the order of 100–200 µm and sandwiched in LC layer thicknesses of ≈10–15 µm, are characterized in terms of their transmission as a function of the electric field amplitude and the response times for switching into and out of the scattering state. The results show that the printed droplets, and arrays thereof, exhibit similar electro‐optical properties to analogous thin‐film devices, but with the ability to incorporate bespoke features such as images and decorative patterns. Finally, the electro‐optical switching of a printed PSCLC privacy window whereby alphanumeric characters can be made to appear and disappear with the application of an electric field is demonstrated.

Droplet quasi-Bessel beam generated with the round-tip axicon: Exact solutions for different axicon shapes

We theoretically investigate droplet quasi-Bessel beams for different shapes of the round-tip axicon. Exact solutions for the Fresnel diffraction integrals describing the axial distribution of the electric field amplitude behind the axicon are demonstrated. The analysis of the exact solutions shows that the period of “light droplets” is not a constant value, but depends on the axial distance and on the deviation of the axicon surface from the conical shape far from the rounded region. The predicted effect can be applied for the reconstruction of the exact shape of the axicon surface without 3D scanning.

Плазмонная природа стоячих микроволн в ближнем поле, позади «дырявых» металлических пластин

This paper is devote to research of microwave electric field patterns behind multilayer metamaterial fishnet structures and multilayer one-dimensional arrays of apertures into near field, closely to holey surface of specimens. Microwave near field patterns of electric field amplitude showed standing waves pictures by some frequencies closely to holey metallic surfaces. May expect that these standing waves serve as the sequent of interference from different plasmon modes which emerge on holey metallic surfaces of slabs as well as into dielectric gaps between them.

Observations of Electron Vorticity and Phase Space Holes in the Magnetopause Reconnection Separatrix

AbstractWe report Magnetospheric Multiscale (MMS) observations of two electron vortices with a roughly 10 km or 2–3 electron skin depths cross‐section across the magnetospheric separatrix of a dayside magnetopause reconnection structure. The enhanced electron vorticity, which is caused by a significant velocity shear in the electron flows streaming in opposite directions along northward‐directed magnetic field lines, leads to perturbations perpendicular to the reconnecting magnetic field on the order of 1–2 nT. The high electron vorticity periods are also associated with electron phase space holes having the largest bipolar parallel electric field amplitudes ∼25 mV/m observed across this exhaust. Less intense ∼10 mV/m electron phase space holes propagate along a northward magnetic field away from the X‐line within a northward reconnection exhaust. The electron phase space holes with the largest bipolar parallel electric fields are observed to propagate toward the X‐line within discrete channels of southward and super‐Alfvénic 1,500 km/s electron flows in the magnetospheric separatrix layer.

Wave breaking field of relativistically intense electrostatic waves in electronegative plasma with super-thermal electrons

The wave breaking limit of relativistically intense electrostatic waves in an unmagnetised electronegative plasma, where electrons are alleged to attach onto neutral atoms or molecules and thus forming a significant amount of negative ions, has been studied analytically. A nonlinear theory has been developed, using one-dimensional (1D) relativistic multi-fluid model in order to study the roles of super-thermal electrons, negative ion species and the Lorentz factor, on the dynamics of the wave. A generalised kappa-type distribution function has been chosen for the velocities of the electrons, to couple the densities of the fluids. By assuming the travelling wave solution, the equation of motion for the evolution of the wave in a stationary wave frame has been derived and numerical solutions have been presented. Studies have been further extended, using standard Sagdeev pseudopotential method, to discover the maximum electric field amplitude sustained by these waves. The dependence of wave breaking limit on the different input parameters such as the Lorentz factor, electron temperature, spectral index of the electron velocity distribution and on the fraction and the mass ratio of the negative to positive ion species has been shown explicitly. The wavelength of these waves has been calculated for a wide range of input parameters and its dependence on aforementioned plasma parameters have been studied in detail. These results are relevant to understand particle acceleration and relativistic wave breaking phenomena in high intensity laser plasma experiments and space environments where the secondary ion species and super-thermal electrons exist.

Multiple polarization-selective and wideband enhanced optical properties of a cubic quantum dot realized by the multi-physical field.

The coupling of intense laser field and electric field serves as a new method to achieve the desired electronic states, optical absorption coefficients and refractive index changes of cubic quantum dot for the first time, to the best of our knowledge. The stationary Schrödinger equation was derived and calculated by means of the Kramers-Henneberger transformation, the non-perturbative Floquet method, and the finite difference method. The energy-level anticrossing is activated by multi-physical field to transform suitable quantum states, resulting in the multiple-polarization-selective absorption and refractive index changes. The results show that ultra-wideband frequency shift and resonance enhancement characteristics of optical absorption coefficients and refractive index changes strongly depend on the laser-dressed parameter, the amplitude of electric field, and the polarization directions of the intense laser field and electric field.

Effect Of Electric Field Modulation On Electroconvection In A Dielectric Fluid-Saturated Porous Medium

<p>The stability of a horizontal sparsely packed porous layer of a dielectric fluid heated from below is examined when the fluid layer is subjected to time-dependent electric field modulation. The dielectric constant is assumed to be a linear function of temperature. The regular perturbation method is used to find the critical Rayleigh number and the corresponding wavenumber for small amplitude electric field modulation. The stability of the system characterized by a correction Rayleigh number is computed as a function of thermal, electric, and porous parameters, and the frequency of electric field modulation. It is found that the onset of electro-convection can be delayed or advanced by the presence of these parameters. The effect of various parameters is found to be significant for moderate values of the frequency of electric field modulation. Some of the known results are recovered as special cases of the present study. The findings of the present study have possible implications in the control of electro-convection with a time-varying electric field.</p>

Temperature and frequency dependent defect dipole kinematics in "hard" piezoelectric ceramics

“Hard” piezoelectric ceramics exhibit typical shifted hysteresis loops due to the presence of oxygen vacancies and defect dipoles. The kinetic characteristics of oxygen vacancies and defect dipoles significantly affect the hardening effect and application scenario of “hard” piezoelectric ceramics. The scaling behavior of the internal bias field is an effective method to investigate the kinetic characteristics of oxygen vacancies and defect dipoles. This work systematically studied the temperature and frequency-dependent relation of the internal bias field in “hard” lead zirconate titanate (PZT-8) ceramics with tetragonal phase. The linear relation of the internal bias field on the temperature and electric field amplitude is given. Simultaneously, the internal bias field exhibits distinct relaxation characteristics with the frequency variation. The stretching relaxation relation between internal bias field and frequency was also determined. In addition, the kinetic characteristics of oxygen vacancy and defect dipole dependent on frequency and temperature were studied and analyzed. Our works provide the scientific theory of defect kinetics for hard-doping perovskite ferroelectrics and guide the device application of “hard” PZT ceramics.

Cross-grating phase microscopy (CGM): In silico experiment (insilex) algorithm, noise and accuracy

Cross-grating phase microscopy (CGM) is a quantitative phase microscopy technique based on the association of a 2-dimensional diffraction grating (aka cross-grating) and a regular camera sensor, separated by a millimetric distance. This simple association enables the high-resolution imaging of the complex electric field amplitude of a light beam (intensity and phase) from a single image acquisition. While CGM has been used for metrology applications in cell biology and nanophotonics this last decade, there has been few studies on its basics, especially for the microscopy community. In this article, we provide a numerical algorithm that enables the in silico (i.e. computer-simulated) data acquisition, to easily vary and observe the effects of all the CGM experimental parameters using computer means. In the frame on this article, we illustrate the interest of this numerical algorithm by using it to explain and quantify the effects of several important CGM parameters (grating-camera distance, pixel size, light intensity, numerical apertures, etc.) on the noise, precision and trueness of CGM measurements. This work is aimed to push the limits of CGM toward advanced applications in biomicroscopy and nanophotonics.

Pulse-to-pulse detection of terahertz radiation emitted from the femtosecond laser ablation process.

Determining the dynamics of electrons and ions emitted from a target material during laser ablation is crucial for desirable control of laser processing. However, these dynamics are still challenging to understand because of a lack of ubiquitous spectroscopic tools to observe tangled-up dynamics appearing at ultrafast timescales. Here by harnessing highly sensitive single-shot terahertz time-domain spectroscopy using an echelon mirror, we investigate pulse-to-pulse temporal profile of terahertz radiation generated from the material surface. We clearly found that the carrier-envelope phase and the electric field amplitude of the terahertz waveform systematically vary between the pre- and post-ablation depending on the laser fluence and irradiated pulse numbers. Our results provide a stepping-stone towards perception of Coulomb explosion occurring throughout the laser ablation process, which is indispensable for future laser processing applications.

Nonlinear magnetoelectric effect in atomic vapor and its application to precision radio-frequency magnetometry

We demonstrate the nonlinear magnetoelectric (ME) effect in atomic vapor achieved through the parametric interaction of optical electric and radio-frequency (rf) magnetic fields leading to the generation of new optical electric fields. Density matrix calculations are performed to validate the experimental results. Moreover, the predicted dependence of the generated optical electric field amplitudes on the rf magnetic field strength is experimentally verified to confirm the ME effect. The system provides a technique for precision rf magnetometry based on this phenomenon. We could experimentally achieve an rf magnetic field sensitivity of 70 $\mathrm{fT}/\sqrt{\text{Hz}}$ at 1 kHz to 7.5 $\mathrm{pT}/\sqrt{\text{Hz}}$ at 3 MHz for zero bias field in an unshielded environment. The appealing features of the proposed rf magnetometer using our system include a high dynamic range up to ${10}^{12}$, 6 dB bandwidth of 450 kHz, and arbitrary frequency resolution, which are intrinsic to the nonlinear ME effect in the medium.

Observation of light-driven band structure via multiband high-harmonic spectroscopy

Intense light–matter interactions have revolutionized our ability to probe and manipulate quantum systems at sub-femtosecond timescales1, opening routes to the all-optical control of electronic currents in solids at petahertz rates2–7. Such control typically requires electric-field amplitudes in the range of almost volts per angstrom, when the voltage drop across a lattice site becomes comparable to the characteristic bandgap energies. In this regime, intense light–matter interaction induces notable modifications to the electronic and optical properties8–10, dramatically modifying the crystal band structure. Yet, identifying and characterizing such modifications remain an outstanding problem. As the oscillating electric field changes within the driving field’s cycle, does the band structure follow and how can it be defined? Here we address this fundamental question, proposing all-optical spectroscopy to probe the laser-induced closing of the bandgap between adjacent conduction bands. Our work reveals the link between nonlinear light–matter interactions in strongly driven crystals and the sub-cycle modifications in their effective band structure.

The Response Mechanism of Borehole Shear-Horizontal Transverse-Electric Seismoelectric Waves to Fluid Salinity

The converted electric field in the seismoelectric effect can be used to monitor the salinity of the reservoir. Compared to some conventional excitation methods (e.g., Monopole source), the response law of borehole shear-horizontal transverse-electric (SH-TE) seismoelectric waves to fluid salinity is unique. In order to explore its physical mechanism, we study the influence of fluid salinity on borehole SH-TE wave fields in this paper. First, to analyze the effect of salinity on the electric field, we simulate the response for different salinity levels inside and outside the borehole. Then we study the wave fields in case of a radial salinity discontinuity outside the borehole, and simulate the interface response by the secant integral method. Finally, we show the feasibility of using the borehole SH-TE wavefields to estimate the salinity interface position combining the slowness-time coherence (STC) method. The results show that the electric field amplitude changes monotonously with the pore fluid salinity level. However, the borehole fluid salinity has almost no effect on the electric field. This is caused by the excitation method and the low frequency of the sound source. An interface converted electromagnetic wave response is generated when an SH wave passes through the salinity discontinuity interface. The interface position estimation examples show that the borehole SH-TE wave field is a potential method to evaluate the behavior and the location of the interface next to the borehole.

DUV coherent light emission from ultracompact microcavity wavelength conversion device.

A unique design of our ultracompact microcavity wavelength conversion device exploits the simple principle that the wavelength conversion efficiency is proportional to the square of the electric field amplitude of enhanced pump light in the microcavity, and expands the range of suitable device materials to include crystals that do not exhibit birefringence or ferroelectricity. Here, as a first step toward practical applications of all-solid-state ultracompact deep-ultraviolet coherent light sources, we adopted a low-birefringence paraelectric SrB4O7 crystal with great potential for wavelength conversion and high transparency down to 130 nm as our device material, and demonstrated 234 nm deep-ultraviolet coherent light generation, whose wavelength band is expected to be used for on-demand disinfection tools that can irradiate the human body.