Intense Electric Field Research Articles

Material normal energy distribution for field emission analyses from monocrystalline surfaces

Electron field emission is a complicated phenomenon which is sensitive not only to the particular material under illumination but also to the specific crystalline orientation of the surface. Summarizing the ability for a crystal to emit in a particular direction would be of great use when searching for good field emitters. In this paper we propose a material normal energy distribution which describes the ability of the bound electrons to tunnel under an intense electric field. This framework breaks a computationally expensive 3-D system down to a source distribution representation applicable for more efficient 1-D models. We use the Fowler-Nordheim framework to study the yield and MTE (mean transverse energy) from sources including gold, copper, and tungsten in both monocrystalline and polycrystalline forms. We find an increase in effective work function for field emission in the (111) direction for gold and copper associated with the Bragg plane intersections of the Fermi surface.

Electro-detachment of kinesin motor domain from microtubule in silico

Kinesin is a motor protein essential in cellular functions, such as intracellular transport and cell-division, as well as for enabling nanoscopic transport in bio-nanotechnology. Therefore, for effective control of function for nanotechnological applications, it is important to be able to modify the function of kinesin. To circumvent the limitations of chemical modifications, here we identify another potential approach for kinesin control: the use of electric forces. Using full-atom molecular dynamics simulations (247,358 atoms, total time ∼ 4.4 μs), we demonstrate, for the first time, that the kinesin-1 motor domain can be detached from a microtubule by an intense electric field within the nanosecond timescale. We show that this effect is field-direction dependent and field-strength dependent. A detailed analysis of the electric forces and the work carried out by electric field acting on the microtubule–kinesin system shows that it is the combined action of the electric field pulling on the β-tubulin C-terminus and the electric-field-induced torque on the kinesin dipole moment that causes kinesin detachment from the microtubule. It is shown, for the first time in a mechanistic manner, that an electric field can dramatically affect molecular interactions in a heterologous functional protein assembly. Our results contribute to understanding of electromagnetic field–biomatter interactions on a molecular level, with potential biomedical and bio-nanotechnological applications for harnessing control of protein nanomotors.

Extensibility of External Magnetic Potential at High Latitudes - Antarctica

We investigated the external magnetic potential due to solar forcing, with nine years of data during 2001-2009, coveringthe deep solar minimum (2006-2009), at two stations: one is in the polar cap -Vostok (78º27'S, 106º52’E; mag. lat 83oS) andanother is in the subauroral region - Maitri (70º45'S, 11º43'E: mag. lat 67oS) in Antarctica. The significance of the work isassociated with space weather prediction and its impact on planet Earth. We used Advance Composition Explorer (ACE)satellite data for the aforesaid period for a thorough understanding of influences due to solar wind origin and to compare theparameter observed in these regions. We used the spherical cap harmonic analysis (SCHA) function as a tool. The inferenceindicates that at Vostok the magnitude is enhanced throughout and depicts a broad ambient external magnetic potential. Itseems to be essentially the intensification of the region 1 currents whereas at Maitri intense electric fields are producedduring geomagnetic perturbations which drive a system of disturbed time Region 2 currents over the quiet time currents.During this scenario in Maitri there are noticeable peaks or enhancements in the magnetic potential that can be observedmainly during geomagnetic disturbances. Hence the regression relation developed for external magnetic potentialcalculation, in terms of solar wind parameters agrees well with polar cap region and the area is relatively less exploredearlier, the present investigation can be expected to add knowledge about that regime.

LiNbO₃ Crystal Intense Electric Field Sensor Coupled With Twisted Polarization Maintaining Fiber

LiNbO₃ Crystal Intense Electric Field Sensor Coupled With Twisted Polarization Maintaining Fiber

High-speed nanoscale optical trapping with plasmonic double nanohole aperture.

Optical trapping with plasmonic double nanohole (DNH) apertures has proven to be an efficient method for trapping sub-50 nm particles due to their suppressed plasmonic heating effect and very high electric field enhancement in the gap region of the aperture. However, plasmonic tweezers are generally diffusion-limited, requiring particles to diffuse down to a few tens of nanometres from the high field enhancement regions before they can be trapped. The loading of target particles to the plasmonic hotspots can take several minutes for diluted samples. In this work, rapid particle transport and trapping of a 25 nm polystyrene sphere is demonstrated, leveraging an electrothermoplasmonic flow induced upon application of an AC field in the presence of a laser-induced temperature gradient. Using this approach, we demonstrate the rapid transport of a 25 nm polystyrene particle across a distance of 63 μm and trapping at the DNH under 16 s. This platform shows great potential for applications involving simultaneous trapping and plasmon-enhanced spectroscopies, such as Raman enhancement via the intense electric field enhancement in the DNH gap.

Optimal Design of an Inductive MHD Electric Generator

In this paper, the problem of optimizing the design of an inductive Magneto-Hydro-Dynamic (MHD) electric generator is formalized as a multi-objective optimization problem where the conflicting objectives consist of maximizing the output power while minimizing the hydraulic losses and the mass of the apparatus. In the proposal, the working fluid is ionized with periodical pulsed discharges and the resulting neutral plasma is unbalanced by means of an intense DC electrical field. The gas is thus split into two charged streams, which induce an electromotive force into a magnetically coupled coil. The resulting generator layout does not require the use of superconducting coils and allows you to manage the issues related to the conductivity of the gas and the corrosion of the electrodes, which are typical limits of the MHD generators. A tailored multi-objective optimization algorithm, based on the Tabu Search meta-heuristics, has been implemented, which returns a set of Pareto optimal solutions from which it is possible to choose the optimal solution according to further applicative or performance constraints.

Terahertz Kerr Effect of Liquids

In recent years, tremendous advancements have been made in various technologies such as far-infrared, low-frequency Raman, and two-dimensional (2D) Raman terahertz (THz) spectroscopies. A coherent method has emerged from numerous experimental and theoretical investigations of molecular dynamics in liquids by comparing linear and non-linear spectroscopic techniques. Intermolecular hydrogen bond vibration, molecular reorientation motion, and interaction between molecule/ionic solute and hydrogen bonds have been demonstrated to occur in the THz region, which are closely related to their physical/chemical properties and structural dynamics. However, precise probing of various modes of motion is difficult because of the complexity of the collective and cooperative motion of molecules and spectral overlap of related modes. With the development of THz science and technology, current state-of-the-art THz sources can generate pulsed electric fields with peak intensities of the order of microvolts per centimeter (MV/cm). Such strong fields enable the use of THz waves as the light source for non-linear polarization of the medium and in turn leads to the development of the emerging THz Kerr effect (TKE) technique. Many low-frequency molecular motions, such as the collective directional motion of molecules and cooperative motion under the constraint of weak intermolecular interactions, are resonantly excited by an intense THz electric field. Thus, the TKE technique provides an interesting prospect for investigating low-frequency dynamics of different media. In view of this, this paper first summarizes the research work on TKE spectroscopy by taking a solid material without low-frequency molecular motions as an example. Starting from the principle of TKE technology and its application in investigating the properties of solid matter, we have explored the low-frequency molecular dynamics of liquid water and aqueous solutions using TKE. Liquid water is a core of life and possesses many extraordinary physical and biochemical properties. The hydrogen bond network plays a crucial role in these properties and is the main reason for its various kinetic and thermodynamic properties, which differ from those of other liquids. However, the structure of the hydrogen bond network between water and solutes is not well known. Therefore, evaluating the hydrogen bond-related kinetic properties of liquid water is important.

Terahertz Sources Based on Metrological‐Grade Frequency Combs

AbstractBroadband metrological‐grade frequency comb (FC) synthesizers with a rich number of phase locked modes are the ideal sources for quantum sensing and quantum metrology. At terahertz (THz) frequencies, electrically pumped quantum cascade lasers (QCLs) have shown quantum‐limited frequency noise operation, phase/frequency absolute referencing and self‐starting FC operation, albeit over a rather restricted dynamic range, governed by the nature of the quantum gain media that entangles group velocity dispersion at the different bias points. Here, a technological approach is conceived to achieve FC operation over the entire available gain bandwidth at THz frequencies. The intracavity light intensity of a multistack QCL, inherently showing a giant Kerr nonlinearity, is altered by increasing the mirror losses of its Fabry‐Perot cavity through coating the back facet with an epitaxially‐grown multilayer graphene film. This enables a frequency modulated THz FC showing a proliferation of emitted modes over the entire gain bandwidth and across more than 60% of its operational range, with ≈0.18 mW per mode optical power. The QCL FC is then experimentally characterized to assess its phase coherence, reconstructing its intensity emission profile, instantaneous frequency, and electric field, thus proving its metrological nature.

Ultrahigh-level enhancement on nonlinear optical susceptibility of cubic quantum dots achieved by THz laser and electric field.

Multi-physics coupling, composed of an intense THz laser and electric field, serves as a new approach to realize the ultrahigh-level enhancement on third-harmonic generation (THG) of cubic quantum dots (CQDs). The exchange of quantum states caused by anticrossing of intersubbands is demonstrated by the Floquet method and finite difference method with the increasing laser-dressed parameter and electric field. The results show that the rearrangement of the quantum states excites the THG coefficient of CQDs four orders of magnitude higher than that achieved with a single physical field. The optimal polarization direction of incident light that maximizes the THG exhibits strong stability along the z axis at high laser-dressed parameter and electric field.

Hydrogenic impurity effect on the optical properties of Ga1-xAlxAs quantum wire under terahertz field

In this study, the effect of impurity factor on the optical absorption coefficients, refractive index changes, second harmonic generation, and third-harmonic generation for the intersubband transitions is explored between the electronic states of Ga1-xAlxAs quantum wire initiated by the symmetric parabolic potential. The system is conquered by the presence of an intense electric field, magnetic field, and Rashba spin-orbit interaction. For the linear and non-linear optical absorption coefficients, refractive index, second harmonic generation, and third harmonic generation coefficient, the analytical expressions are obtained with the assistance of the compact density-matrix approach. The arithmetical outcomes illustrate the optical properties are significantly intuitive to the concentration of impurity and can be controlled by this parameter. The variation in the magnitude and position of peaks via impurity factor indicates the opportunity in the mechanism of optical non-linearity in the quantum wire and also, helps in the optical non-linearity tuning which has device application.

MODL-13. Sensitivity of Tumor Treating Fields (TTFields) treatment planning to healthy tissue segmentation inaccuracies

Abstract TTFields are FDA approved for treating patients with GBM. TTFields utilize low intensity electric fields with intermediate frequency (100-500 kHz) that disrupt cellular processes critical for cancer cell viability and tumor progression. TTFields have been shown to disrupt multiple phases of the cell cycle including metaphase, anaphase, and telophase, resulting in cellular apoptosis. TTFields are administered through two pairs of capacitive arrays placed on the patient’s scalp. As TTFields are a dose dependent therapy, optimization of array layout for maximizing field intensity may improve survival rates of patients. Thus, Novocure is developing a treatment planning system, in which MR images are used to create a patient-specific model, which in turn is used for simulating electric fields distribution. However, the segmentation process of the MRIs is prone to errors that may influence the choice of array layout, and consequently provide lower TTFields dose than possible. To test the sensitivity of layout chosen to such inaccuracies, we placed different array layouts on the highly detailed MIDA head model and simulated the resulting LMiPD from each configuration. We then simplified the model in several phases and compared the resulting array layout ranking between the full model and each simplified model. Our results show that though the calculated LMiPD is very sensitive to the quality of the model, the ranking pattern between the detailed and simplified models is similar. Some alterations do occur, but this mostly happens when the LMiPD values between switched layouts are very close, rendering these alterations clinically insignificant. Based on these results, we conclude that the ranking order of array layouts by LMiPD dose does not significantly change between detailed and simplified head models even though the LMiPD dose itself is sensitive to the quality of the head model.

INNV-11. EIGHTEEN YEARS OF EXPERIENCE WITH TREATMENT OF GLIOBLASTOMA USING TUMOR TREATING FIELDS (TTFIELDS) IN NEWLY DIAGNOSED GLIOBLASTOMA (NDGBM) IN A SINGLE CENTER

Abstract Despite considerable progress in the management of many malignant tumors, the prognosis of the most malignant primary brain tumor, GBM, remains unfavorable. TTFields utilize low intensity electric fields with intermediate frequency (100–500 kHz) that act as an antimitotic, selectively inhibiting growth of rapidly dividing tumor cells by disrupting multiple phases of the cell cycle (metaphase, anaphase, and telophase) resulting in cellular apoptosis. TTFields are delivered via arrays of transducers placed on the patients’ scalp. Between 2004 and August 2021, 54 patients (KPS ≥, 20 female), aged 21.85–77.77 years (mean age 47.41 ± 11.92 years; median 47.88 years) were treated with TTFields for ndGBM, and compared to 52 control patients (15 females); aged 27.03–76.67 years (mean age 51.38 ± 12.55 years; median 51.74 years. All patients from both groups underwent gross total or partial resection of GBM. When available, MGMT promoter methylation status was comparable in both groups. The most frequent AE from TTFields therapy was skin irritation at the array site that usually responded to local corticosteroid application. Patients on TTFields therapy demonstrated improvements in PFS and OS relative to controls (hazard ratio: 0.55, p=0.006; and 0.61, p=0.027 respectively). TTFields average time on therapy was 74.8% (median 82%): median PFS of these patients was 18.16 months. Seven patients with TTFields usage ≤ 60% (23–60%, mean 46.3%, median 53%) had a median PFS of 7.95 months (p=0.0356). Control patients with no TTFields exposure had a median PFS of 11.04 months. In conclusion, this is one of the most extensive studies of ndGBM patients treated with TTFields, covering a period of 18 years in a single center. We demonstrate positive effects of TTFields on both PFS and OS in patients with ndGBM.

Generating intense electric fields in 2D materials by dual ionic gating

The application of an electric field through two-dimensional materials (2DMs) modifies their properties. For example, a bandgap opens in semimetallic bilayer graphene while the bandgap shrinks in few-layer 2D semiconductors. The maximum electric field strength achievable in conventional devices is limited to ≤0.3 V/nm by the dielectric breakdown of gate dielectrics. Here, we overcome this limit by suspending a 2DM between two volumes of ionic liquid (IL) with independently controlled potentials. The potential difference between the ILs falls across an ultrathin layer consisting of the 2DM and the electrical double layers above and below it, producing an intense electric field larger than 4 V/nm. This field is strong enough to close the bandgap of few-layer WSe2, thereby driving a semiconductor-to-metal transition. The ability to apply fields an order of magnitude higher than what is possible in dielectric-gated devices grants access to previously-inaccessible phenomena occurring in intense electric fields.

Dielectrophoretic influence on free convection in a differentially heated cavity

The modification of the natural convective flow in a differentially heated cavity by means of a steady dielectrophoretic torque is investigated experimentally and numerically. This torque is produced within a dielectric liquid by imposing a high frequency alternating voltage between two opposite asymmetric electrodes located at the side walls of the cavity. The electrodes are also submitted to a temperature difference. A specific staggered configuration of the electrodes creates non homogeneous electric and temperature fields. Increasing velocities are observed with increasing voltage in the regions of intense electric fields. Subsequent modifications of the flow pattern are noted with a loss of symmetry and the reinforcement of secondary vortices. Although the magnitude of the dielectrophoretic torque is modest compared to the thermal buoyancy torque, up to 8% increase in convective heat transfer is calculated for the highest Rayleigh and Roberts numbers. This steady contribution of dielectrophoretic forces to internal free convective flows open the door to an electrode geometry optimization so as to achieve a better heat transfer enhancement and to the generation of convective flows in microgravity conditions.

Electrofreezing of Liquid Ammonia.

Here we prove that, in addition to temperature and pressure, another important thermodynamic variable permits the exploration of the phase diagram of ammonia: the electric field. By means of (path integral) ab initio molecular dynamics simulations, we predict that, upon applying intense electric fields on ammonia, the electrofreezing phenomenon occurs, leading the liquid toward a novel ferroelectric solid phase. This study proves that electric fields can generally be exploited as the access key to otherwise-unreachable regions in phase diagrams, unveiling the existence of new condensed-phase structures. Furthermore, the reported findings have manifold practical implications, from the safe storage and transportation of ammonia to the understanding of the solid structures this compound forms in planetary contexts.

Dynamic behaviour of a suspended bubble and its influence on the distribution of electric fields in insulating oil of an on-load tap-changer within power transformers

A small amount of gas bubbles generated in an on-load tap changer (OLTC) can cause partial discharges in the intense electric field region, which severely threaten the safe operation of the device. It is crucial to clarify the coupling mechanism of moving bubbles together with the electric field distribution in the OLTC. This paper analyzed the internal structure and operating principle of the OLTC switching core and clarified the electric field distribution of each component under working conditions. A 2D two-phase flow model was established based on a practical OLTC structure by using the phase-field method. We investigated the global dynamics of small bubbles in the OLTC under the combined action of flow and electric fields and generalized the mechanism of their impact on the spatiotemporal distribution of the electric field inside the OLTC. Finally, the influence of the characteristic parameters of the bubbles and the insulating oil on the insulation property of the OLTC were clarified. The results showed that the distribution of the electric field was closely related to the shapes of the bubbles and the initial field strength. When the oil quality was poor, there was a risk that the bubbles caused partial discharge, in which case, oil purification and filtration operations should take place. The oil flow velocity should be controlled within a specific range to ensure that the rapid passage of bubbles through the intense electric field area does not render distortions in the field strength significant. The smaller the bubble size is, the steeper the gradient of electric field becomes at the gas-oil interface, and the greater the field strength inside the bubble, more likely to cause the occurance of accidental discharges in the OLTC.

Temperature effects on Manakov solitons in biased photorefractive crystals exhibiting the linear and quadratic electro-optic effect simultaneously

We investigate the effect of temperature on Manakov solitons in biased photorefractive crystals having both linear and quadratic electro-optic effects simultaneously. Two different physical quantities, namely, the dielectric constant and the dark irradiance, have a temperature dependence which in turn affects the Manakov solitons. We consider three realizations of the Manakov solitons for our present analysis, namely, the bright–bright, dark–dark and bright–dark Manakov soliton pair. The existence curve and its modification due to temperature has been studied in detail for each of the Manakov soliton pair. A comprehensive investigation of the functional dependence of the soliton width with temperature is undertaken for different parameters like beam intensity and external electric field for each of the Manakov soliton pair. The tuning of photorefractive soliton characteristics by changing of temperature has potential practical applications in optical networks and optical waveguiding.

Pattern Recognition Directed Assembly of Plasmonic Gap Nanostructures for Single-Molecule SERS.

Gold nanocubes (AuNCs) with tunable localized surface plasmon resonance properties are good candidates for plasmonic gap nanostructures (PGNs) with hot spots (areas with intense electric field localization). Nevertheless, it remains challenging to create shape-controllable nanogaps between AuNCs. Herein, we report a DNA origami directed pattern recognition strategy to assemble AuNCs into PGNs. By tuning the position and number of capture strands on the DNA origami template, different geometrical configurations of PGNs with nanometer-precise and shape-controllable gaps are created. The localized field enhancement in these gaps can generate hot spots that are in accordance with finite difference time domain simulations. Benefiting from the single Raman probe molecule precisely anchored at these nanogaps, the dramatic enhanced electromagnetic fields localized in hot spots arouse stronger single-molecule SERS (SM-SERS) signals. This method can be utilized in the design of ultrahigh-sensitivity photonic devices with tailored optical properties and SERS-based applications.

Ultrafast Terahertz Self-Induced Absorption and Phase Modulation on a Graphene-Based Thin Film Absorber

Interaction of intense terahertz (THz) waves with graphene based modulation devices holds great potential for the optoelectronic applications of the future. Here, we present a thin film graphene-based THz perfect absorbing device whose absorption and phase characteristics can be modulated through THz self-actions in the subps time scale. The device consists of a single-layer graphene placed on an ionic liquid substrate, back-plated by a metallic back-reflector, with the graphene doping level mediated through electrostatic gating. We experimentally record an absorption modulation of more than 3 orders of magnitude from the initial perfect absorption state, when the device is illuminated with THz field strengths in the range of 102 to 654 kV/cm. Furthermore, an absolute phase modulation of 130° is recorded. Detailed theoretical analysis indicates that the origin of the THz nonlinear response is the THz-induced heating of the graphene’s carriers that leads to a reduction of its conductivity and, consequently, to reduced absorption of the THz radiation. Our analysis also maps the temporal dynamics of the THz-induced temperature elevation of the graphene’s carriers, illustrating the ultrafast, subps nature of the overall process. These results can find applications in future dynamically controlled flat optics and spatiotemporal shaping of intense THz electric fields.

Investigating the valence-band bound states in GaAs/GaAsSb/GaAs V-shaped quantum wells: The role of intense laser fields and position-dependent effective mass

This theoretical study investigated the valence-band electronic features in GaAs/GaAsSb/GaAs V-shaped quantum wells. Accordingly, an analytical relation has been extended on the position-dependent effective mass in GaAsSb well region as a function of well geometry. The Finite Element Method and the effective mass approximation have been used to investigate the combined effects due to a non-resonant high-frequency intense laser field and an applied electric field. This study considered the effects of geometric and structural parameters on the laser-dressed confining potential profile, bound states, and the corresponding wave functions. The performed studies have shown that the laser-dressing could convert a V-shaped potential profile to a parabolic-like potential and also a single-well to a double-well. The combined effects of intense laser and electric fields have caused a conversion from a symmetric well to a larger and shallower asymmetric structure. It has been found from the valence-band energy levels that pronounced blueshifts and redshifts were obtained in the electromagnetic energy spectrum with increasing the strength of the intense laser and applied electric fields, respectively. The numerical results have indicated that the electronic properties in valence-band quantum wells were modulated according to the purpose through varying the well half-width and the antimony concentration. Such adjustable valence-band-based features can be beneficial in the design and fabrication of the next generation equipment used in the optoelectronic domain.