Visualized measurement of the electric field in large aperture LiNbO3 crystal by digital holographic interferometry

The electric field distribution in Li Nb O3 crystal under different electrode shape is presented by using the digital holographic interferometry. Three configurations of phase modulator including the rectangular electrode type,single-triangle electrode type, and dual-triangle electrode type are performed in this experiment. The nonuniform electric field distribution in these phase modulators are observed and the electric field increases with voltage increasing. The digital holographic interferometry with high electro-optic effect improves the measurement precision. The digital holographic interferometry provides an effective way for studying the electric field distribution. Such in situ quantitative analysis of electric field distribution is a key to optimizing electrode shape.     

Multi-bubble motion behavior of electric field based on phase field model

By coupling the phase field model with the continuity equation of incompressible fluid, Navier–Stokes equation,electric field equation, and other governing equations, a multi-field coupling model for multi-bubble coalescence in a viscous fluids is established. The phase field method is used to capture the two-phase interface. The motion and coalescence of a pair of coaxial bubbles under an external uniform electric field and the effects of different electric field strengths on the interaction and coalescence of rising bubbles are studied. The results show that the uniform electric field accelerates the collision and coalescence process of double bubbles in the fluid, and increases the rising velocity of the coalesced bubble.The electric field with an intensity of E = 2 kV/mm is reduced about 2 times compared with that without electric field in coalescence time. When the electric field strength is strong(E ≥ 1 kV/mm), the coalesced bubble will rupture before it rises to the top of the calculation area, and the time of the bubble rupturing also decreases with the increase of the electric field strength. The phase field method is compared with the simulation results of Lattice Boltzmann Method(LBM), and the shape of bubble obtained by the two methods is in good agreement, which verifies the correctness of the calculation model.     

Resonances of a hydrogen atom in strong parallel electric and magnetic fields using B-spline basis sets

The B-spline basis set plus complex scaling method is applied to the numerical calculation of the exact resonance parameters Er and Г/2 of a hydrogen atom in parallel electric and magnetic fields. The method can calculate the ground and higher excited resonances accurately and efficiently. The resonance parameters with accuracies of 10^-9 - 10^-12 for hydrogen atom in parallel fields with different field strengths and symmetries are presented and compared with previous ones. Extension to the calculation of Rydberg atom in crossed electric and magnetic fields and of atomic double excited states in external electric fields is discussed.     

Intensity modulation of light by light in a periodically poled MgO-doped lithium niobate crystal

In this Letter, we investigate a method for controlling the intensity of a light by another light in a periodically poled MgO-doped lithium niobate(PPMgLN) crystal with a transverse applied external electric field. The power of the emergent light can be modulated by the power ratio of the incident ordinary and extraordinary beams. The light intensity control is experimentally demonstrated by the Mach–Zehnder interference configuration, and the results are in good agreement with the theoretical predictions.     

Pseudospectral method with symplectic algorithm for the solution of time-dependent SchrSdinger equations

A pseudospectral method with symplectic algorithm for the solution of time-dependent Schrodinger equations （TDSE） is introduced. The spatial part of the wavefunction is discretized into sparse grid by pseudospectral method and the time evolution is given in symplectic scheme. This method allows us to obtain a highly accurate and stable solution of TDSE. The effectiveness and efficiency of this method is demonstrated by the high-order harmonic spectra of one-dimensional atom in strong laser field as compared with previously published work. The influence of the additional static electric field is also investigated.     

Controlling beam halo-chaos via backstepping design

A backstepping control method is proposed for controlling beam halo-chaos in the periodic focusing channels （PFCs） of high-current ion accelerator. The analysis and numerical results show that the method, via adjusting an exterior magnetic field, is effective to control beam halo chaos with five types of initial distribution ion beams, all statistical quantities of the beam halo-chaos are largely reduced, and the uniformity of ion beam is improved. This control method has an important value of application, for the exterior magnetic field can be easily adjusted in the periodical magnetic focusing channels in experiment.     

Near-field lithography on the azobenzene polymer liquid crystal films

In this article, we reported near-field research on azobenzene polymer liquid crystal films using scanning near-field optical microscopy (SNOM). Optical writing and subsequently topographic reading of the patterns with subwavelength resolution were carried out in our experiments. Nanometer scale dots and lines were successfully fabricated on the films and the smallest dot diameter is about 120 nm. The width of the line fabricated is about 250 nm. This method is also a choice for nanolithography. The mechanism of the surface deformation on the polymer films was briefly analyzed from the viewpoint of gradient force in the optical near field. The intensity distribution of the electric field near the tip aperture was numerically simulated using finite-difference time-domain (FDTD) method and the numerical simulation results were consistent with the experimental results.     

The stress field and energy of screw dislocation in smectic A liquid crystals and the mistakes of the classical solution

The mistakes in the classical solution of a screw dislocation in smectic A liquid crystals are pointed out. A serious problem with the well-known theory is pointed, which may be named de Gennes-Kleman-Pershan paradox and has existed for many decades in the scientific community of liquid crystal study. The correct solution is given in this paper by a simplest, elementary, and straight forward method. In connection with this, the stress field and energy of dislocation are discussed in detail. The present article provides the correct stress field and dislocation energy as well.     

Full-vectorial analysis of optical waveguides by the finite difference method based on polynomial interpolation

Based on the polynomial interpolation, a new finite difference (FD) method in solving the full-vectorial guided-modes for step-index optical waveguides is proposed. The discontinuities of the normal components of the electric field across abrupt dielectric interfaces are considered in the absence of the limitations of scalar and semivectorial approximation, and the present FD scheme can be applied to both uniform and non-uniform mesh grids. The modal propagation constants and field distributions for buried rectangular waveguides and optical rib waveguides are presented. The hybrid nature of the vectorial modes is demonstrated and the singular behaviours of the minor field components in the corners are observed. Moreover, solutions are in good agreement with those published early, which tests the validity of the present approach.     

Molecular properties and potential energy function model of BH under external electric field

Using the density functional B3P86/cc-PV5Z method, the geometric structure of BH molecule under different external electric fields is optimized, and the bond lengths, dipole moments, vibration frequencies, and other physical properties parameters are obtained. On the basis of setting appropriate parameters, scanning single point energies are obtained by the same method and the potential energy curves under different external fields are also obtained. These results show that the physical property parameters and potential energy curves may change with external electric field, especially in the case of reverse direction electric field. The potential energy function without external electric field is fitted by Morse potential, and the fitting parameters are obtained which are in good agreement with experimental values. In order to obtain the critical dissociation electric parameter, the dipole approximation is adopted to construct a potential model fitting the corresponding potential energy curve of the external electric field. It is found that the fitted critical dissociation electric parameter is consistent with numerical calculation, so that the constructed model is reliable and accurate. These results will provide important theoretical and experimental reference for further studying the molecular spectrum, dynamics, and molecular cooling with Stark effect.     

Preliminary analysis of resonance effect by Helmholtz-SchrSdinger method

The Helmholtz SchrSdinger method is employed to study the electric field standing wave caused by coupling through a simple slot. There is a good agreement between the numerical results and the resonant conditions presented by the Helmholtz-Schrodinger method. Thus, it can be used in similar cases where the amplitude of the electric field is the important quantity or eigenfunctions of the Schrodinger equation are needed for complicated quantum structures with hard wall boundary conditions.     

Properties and Structure of a Plasma Non-Neutral Shock

The shock is described by the Navier-Stokes equations of the electron and ion fluids, and coupled with Poisson‘s equation for the self-induced electric field. Profiles of the flow and electric variables in the weak or moderate shock front with or without current for different Debye lengths are presented. Comparison of profiles of flow and electric variables in the front for different heat flow modes is given.     

Modeling electric field of power metal-oxide-semiconductor field-effect transistor with dielectric trench based on Schwarz–Christoffel transformation

A power metal-oxide-semiconductor field-effect transistor(MOSFET) with dielectric trench is investigated to enhance the reversed blocking capability. The dielectric trench with a low permittivity to reduce the electric field at reversed blocking state has been studied. To analyze the electric field, the drift region is segmented into four regions, where the conformal mapping method based on Schwarz–Christoffel transformation has been applied. According to the analysis, the improvement in the electric field for using the low permittivity trench is mainly due to the two electric field peaks generated in the drift region around this dielectric trench. The analytical results of the electric field and the potential models are in good agreement with the simulation results.     

Built-in electric field effect on cyclotron mass of magnetopolarons in a wurtzite In_xGa_（1-x）N/GaN quantum well

The cyclotron mass of magnetopolarons in wurtzite In x Ga 1 x N/GaN quantum well is studied in the presence of an external magnetic field by using the Larsen perturbation method.The effects of the built-in electric field and different phonon modes including interface,confined and half-space phonon modes are considered in our calculation.The results for a zinc-blende quantum well are also given for comparison.It is found that the main contribution to the transition energy comes from half-space and interface phonon modes when the well width is very small while the confined modes play a more important role in a wider well due to the location of the electron wave function.As the well width increases,the cyclotron mass of magnetopolarons first increases to a maximum and then decreases either with or without the built-in electric field in the wurtzite structure and the built-in electric field slightly reduces the cyclotron mass.The variation of cyclotron mass in a zinc-blende structure is similar to that in a wurtzite structure.With the increase of external magnetic field,the cyclotron mass of polarons almost linearly increases.The cyclotron frequency of magnetopolarons is also discussed.     

Tunable negative-index photonic crystals using colloidal magnetic fluids

The model of using colloidal magnetic fluid to build tunable negative-index photonic crystal is established. The effective permittivity εe and permeability μe of the two-dimensional photonic crystal are investigated in detail. For transverse magnetic polarization, both εe and μe exhibit a Lorentz-type anomalous dispersion, leading to a region where εe and μe are simultaneously negative. Then, considering a practical case, in which the thickness of photonic crystal is finite, the band structures for odd modes are calculated by the plane wave expansion method and the finite-difference time-domain method. The results suggest that reducing the external magnetic field strength or slab thickness will weaken the periodic modulation strength of the photonic crystal. Simulation results prove that the negative-index can be tuned by varying the external magnetic field strength or the slab thickness. The work presented in this paper gives a guideline for realizing the flat photonic crystal lens with tunable properties at optical frequencies, which may have potential applications in tunable near-field imaging systems.     

Analysis of two-dimensional photonic band gap structure with a rhombus lattice

The relative band gap for a rhombus lattice photonic crystal is studied by plane wave expansion method and high frequency structure simulator(HFSS)simulation.General wave vectors in the first Briliouin zone are derived.The relative band gap as a function of air-filling factor and background material is investigated,respectively,and the nature of photonic band gap for different lattice angles is analyzed by the distribution of electric energy.These results would provide theoretical instruction for designing optical integrated devices using photonic crystal with a rhombus lattice.     

Dispersion characteristics of two-dimensional unmagnetized dielectric plasma photonic crystal

This paper studies dispersion characteristics of the transverse magnetic (TM) mode for two-dimensional unmagnetized dielectric plasma photonic crystal by a modified plane wave method. First, the cutoff behaviour is made clear by using the Maxwell--Garnett effective medium theory, and the influences of dielectric filling factor and dielectric constant on effective plasma frequency are analysed. Moreover, the occurence of large gaps in dielectric plasma photonic crystal is demonstrated by comparing the skin depth with the lattice constant, and the influence of plasma frequency on the first three gaps is also studied. Finally, by using the particle-in-cell simulation method, a transmission curve in the \Gamma -X direction is obtained in dielectric plasma photonic crystal, which is in accordance with the dispersion curves calculated by the modified plane wave method, and the large gap between the transmission points of 27~GHz and 47~GHz is explained by comparing the electric field patterns in particle-in-cell simulation.     

Electromagnetic simulation study of dielectric wall accelerator structures

Two types of dielectric wall accelerator (DWA) structures, a bi-polar Blumlein line and zero integral pulse line (ZIP) structures were investigated. The high gradient insulator simulated by the particle in cell code con rms that it has little in uence on the axial electric field. The results of simulations using CST microwave studio indicate how the axial electric field is formed, and the electric eld waveforms agree with the theoretical one very well. The in uence of layer-to-layer coupling in a ZIP structure is much smaller and the electric eld waveform is much better. The axial of the Blumlein structure's electric field has better axial stability. From both of the above, it found that for a shorter pulse width, the axial electric field is much higher and the pulse stability and delity are much better. The CST simulation is very helpful for designing DWA structures.     

Spin-1 Blume-Capel model with longitudinal random crystal and transverse magnetic fields：A mean-field approach

The spin-1 Blume-Capel model with transverse and longitudinal external magnetic fields h, in addition to a longitudinal random crystal field D, is studied in the mean-field approximation. It is assumed that the crystal field is either turned on with probability p or turned off with probability 1 p on the sites of a square lattice. Phase diagrams are then calculated on the reduced temperature crystal field planes for given values of γ=Ω/J and p at zero h. Thus, the effect of changing γ and p are illustrated on the phase diagrams in great detail and interesting results are observed.     

Preliminary analysis of resonance effect by Helmholtz Schrdinger method

The Helmholtz-Schrdinger method is employed to study the electric field standing wave caused by coupling through a simple slot. There is a good agreement between the numerical results and the resonant conditions presented by the Helmholtz-Schrdinger method. Thus, it can be used in similar cases where the amplitude of the electric field is the important quantity or eigenfunctions of the Schrdinger equation are needed for complicated quantum structures with hard wall boundary conditions.