Generation and amplification of electromagnetic waves by an annular electron beam in a radial electric field in free space

Mechanisms for the generation and amplification of electromagnetic waves by a thin-walled annular beam of electrons rotating in a radial electric field in free space are studied theoretically. It is shown that electromagnetic waves can be generated and amplified under the Cherenkov resonance conditions. The frequencies and growth rates of the generated waves are determined, and the propagation characteristics and amplification coefficients of the amplified waves are found.     

Eigen electromagnetic waves of a coaxial waveguiding structure filled by a non‐uniform dissipative plasma with azimuthal magnetic field

This paper studies the propagation and spatial attenuation of high‐frequency eigen‐symmetric and dipolar electromagnetic waves along a coaxial plasma–metal waveguiding structure that contains a slightly axial and strong radial non‐uniform cylindrical plasma slab in an external azimuthal non‐uniform magnetic field. The influence of such parameters as the effective electron collision frequency, the direct current value producing the external azimuthal magnetic field, parameters that characterize plasma density radial profile, and waveguide geometric parameters on the dispersion, spatial attenuation, and radial field structure of the waves is considered. The regions of waveguiding structure parameters where the electromagnetic wave properties can be effectively controlled are studied and analyzed.     

Scattering from an elliptical cylindrical plasma for electromagnetic waves with wavelength much greater than the dimensions of the plasma cross-section

The distribution of the electric potential inside and outside a cold plasma column with elliptical cross-section when electromagnetic waves scatter from it are obtained. It is assumed that the wavelength of incident wave is much greater than the dimensions of the cross section of the plasma column. The electrical potential inside and outside a magnetized elliptical plasma column for an anisotropic scattering process are obtained. The graphs of the ratio of the electric field inside the plasma and the incident electric field versus the incident angle, the geometrical dimension of the elliptical plasma column and cyclotron frequency are presented separately. Finally, scattering of the same waves from an elliptical cylindrical inhomogeneous isotropic cold plasma is also investigated.     

Effect of drifting carriers on longitudinal electro-kinetic waves in ion-implanted semiconductor plasmas

We present an analytical study of wave spectra of electro-kinetic waves propagating through semiconductor plasma, whose main constituents are drifting electrons, holes and non-drifting negatively charged colloids. By employing the hydrodynamical model of multi-component plasma, a compact dispersion relation for the same is derived. This dispersion relation is used to study slow electro-kinetic wave phenomena and resultant instability numerically. We find some important modifications in the wave spectra of the slow electro-kinetic branch. It is found that the drift velocities of electrons and holes are responsible for converting two aperiodic modes into periodic ones. The applied dc electric field increases the phase velocities of contra-propagating modes. The amplification coefficients of propagating modes can be optimized by tuning the amplitude of applied electric field and wave number. It is hoped that the results of this investigation should be useful in understanding the wave spectra of slow electro-kinetic waves in ion-implanted semiconductor plasma subjected to a dc electric field along the direction of wave propagation.     

Determination of the wave number of an electromagnetic wave propagating in high-frequency jet discharge plasma

The measurements of the amplitude-phase characteristics of the electromagnetic field in a high-frequency jet discharge burning in air and argon have been performed. Experimentally obtained radial distributions of the radial component of the electric field gave the base to determine the value of the wave number of an electromagnetic wave which propagates in the HF jet discharge plasma. The axial distribution of the radial component of the electric field has been calculated from the model of a jet discharge channel formed as a finite-length electric line.     

Electric-field-induced features of propagation and localization of <Emphasis Type="Italic">S</Emphasis>-polaritons in a gyrotropic 1D magnetic photonic crystal

The effect of the quadratic magnetooptical interaction on the refraction of volume electromagnetic TE waves incident from outside onto the surface of a 1D photonic crystal of the easy-axis ferromagnet-nonmagnetic dielectric type in an external dc electric field.     

Low-Frequency Radiation from an Axisymmetric Current in an Ionospheric Plasma

We consider the radiation of low-frequency electromagnetic waves from an axisymmetric current and propagation of these waves in a homogeneous ionospheric plasma with Hall and Pedersen conductivities. We obtain an analytical expressions for the fields excited by pulsed radial and ring currents. It is shown that electromagnetic radiation propagates as a wave inside a cone along the magnetic field. The field propagation outside the cone is described by a diffusion law. The spatio-temporal characteristics of the signal are determined by the ionospheric conductivities.     

Mutual rectification of alternating currents in graphene in the field of two electromagnetic waves

For graphene placed in a dc magnetic field and exposed to two electromagnetic waves of the same polarization but different frequencies, an expression for the direct current density in a direction perpendicular to the polarization plane of the waves is derived. The direct current component is nonzero for the wave frequency ratio equal to two; it is proportional to the magnetic field strength, the electric field strength of the higher-frequency wave, and the squared electric field strength of the lower-frequency wave. The physical mechanism of the current generation is similar to the Hall effect.     

磁场对螺旋波等离子体波和能量吸收影响的数值研究

本文考察在径向电子数密度呈抛物形分布的情况下,外加稳恒磁场,射频通过螺旋波天线在等离子体中激发电磁波的传播性质.采用线性扰动波假设,数值求解Maxwell方程组,得到80—800 G(1 G=10-4T)磁场条件下等离子体中径向电、磁场强度及能量沉积密度的分布情形.计算结果表明,磁场增大(80→800G)时,螺旋波受到的阻尼较小,可深入等离子体传播;Trivelpiece-Gould(TG)波受到的阻尼增大,在等离子体-真空边界处衰减增强;整体的能量吸收向边界集中.磁感应强度小于100 G时,TG波可深入主等离子体区传播,等离子体径向能量吸收相对均匀.     

Transverse wave propagation in relativistic two-fluid plasmas around Reissner–Nordström–de Sitter black hole

The transverse electromagnetic waves propagating in a relativistic two-fluid plasma influenced by the gravitational field of the Reissner–Nordström–de Sitter black hole has been investigated exploiting “3 + 1” split of spacetime. Reformulating the two-fluid equations, the set of simultaneous linear equations for the perturbations have been derived. Using a local approximation, the one-dimensional radial propagation of Alfvén and high frequency electromagnetic waves are investigated. The dispersion relation for these waves is obtained and solved numerically for the wave number.     

Radioelectric effect in a superlattice under the action of an elliptically polarized electromagnetic wave

The density of the current associated with the drag of charge carriers in a superlattice by an elliptically polarized electromagnetic wave is calculated. Two cases of the mutual orientation of the Umov-Poynting vector and the superlattice axis, i.e., their parallel and perpendicular orientations, are analyzed. It is shown that, for the parallel orientation, the radioelectric effect can change sign. The influence of the longitudinal dc electric field on the radioelectric effect is investigated under the conditions where a circularly polarized electromagnetic wave propagates along the superlattice axis. The current density is studied as a function of the electric field strength and the electromagnetic wave intensity. It is demonstrated that the direction of the electric current is changed at specific values of the dc field strength and the wave intensity.     

A tunable terahertz-band oscillator based on a two-well nanostructure with a coherent electron subsystem

A theory of coherent resonance tunneling of electrons in a two-well nanostructure (TWNS) in the presence of a strong electromagnetic field is developed. The TWNS consists of two identical tunnel-coupled quantum wells to which a dc electric field is applied. Radiative transitions occur between two levels that arise due to the interwell interference and the dc electric field. The wavefunctions and polarization currents in the TWNS are found in the case of a strong electromagnetic field, and the oscillation power is determined as a function of the coherent pumping current and the parameters of the structure. It is shown that oscillations are possible in the relevant terahertz band, with fine frequency tuning by a dc field. It is found that the interference of electrons between quantum wells plays a crucial role. This interference significantly suppresses the effect of the electromagnetic field on the resonance tunneling and enhances the oscillation up to the highest possible level. It is proved that there exists an optimal regime of strong-field oscillations without inverse population and saturation, which are inherent in conventional lasers.     

Generation of electromagnetic waves by a rotating plasma

Generation of electromagnetic waves by an annular shell of plasma rotating in crossed radial electrostatic and axial magnetic fields in a cylindrical resonator is investigated theoretically. Dispersion relations are obtained describing the interaction of the waves with the plasma. It is shown that generation of waves by a narrow plasma shell is possible due to a cyclotron resonance, Čerenkov resonance, or plasma resonance. Here we consider a Čerenkov resonance, where the velocities of the plasma components and the phase velocities of the waves are perpendicular to the constant magnetic field. The frequencies and growth rates of the waves are found under conditions of the above-mentioned resonances in a uniform and in a nonuniform plasma shell. Advantages and disadvantages of wave generation under various conditions are noted. Zh. Tekh. Fiz. 69, 16–21 (February 1999)     

Effect of transverse entrainment of charge carriers by the field of two electromagnetic waves in a semiconductor

The effect of transverse entrainment of charge carriers by two electromagnetic waves propagating in mutually perpendicular directions in a semiconductor with a parabolic dispersion law has been investigated. The dc component of the electric current density that appears in the direction perpendicular to the wave vectors has been calculated in the constant relaxation time approximation. It has been shown that the transverse dc current vanishes at a particular phase difference of the incident waves determined by the relaxation time of charge carriers in the material.     

Modeling the triggering of streamers in air by ultrashort laserpulses

The physical processes involved in the triggering of ionization waves (streamers) by ultrashort laser pulses, focused in air at 350 Torr and in a uniform electric field, are investigated by means of a one-dimensional (1-D) numerical model. The model describes the interaction of the laser pulse with air and takes into account many of the reactions in the laser-created plasma as well as the radial expansion of the plasma. Consequences of the model are that the threshold electric field for the appearance of streamers is an increasing function of the delay between the laser pulse and the electric field pulse and a decreasing function of the laser energy. Also, it appears that the electron temperature, the plasma density and radius, and the conduction of heat across the plasma boundaries play major roles in the capacity of the laser-created plasma to trigger streamers. The results of the model are compared with the available experimental data     

Electromagnetic interaction between local surface plasmon polaritons and an atmospheric surface wave plasma jet

We analyze the electromagnetic interaction between local surface plasmon polaritons （SPPs） and an atmospheric surface wave plasma jet （ASWPJ） in combination with our designed discharge device. Before discharge, the excitation of the SPPs and the spatial distribution of the enhanced electric field are analyzed. During discharge, the critical breakdown electric field of the gases at atmospheric gas pressure and the surface wave of the SPPs converted into electron plasma waves at resonant points are studied. After discharge, the ionization development process of the ASWPJ is simulated using a two- dimensional fluid model. Our results suggest that the local enhanced electric field of SPPs is merely the precondition of gas breakdown, and the key mechanism in maintaining the discharge development of a low-power ASWPJ is the wave-mode conversion of the local enhanced electric field at the resonant point.     

Fourier synthesization of optical pulses and “polar” light

It is shown that the direct Fourier synthesization of light beams allows one to create polarity-asymmetric waves, which are able, in the process of nonlinear interaction with a medium, to break its inversion symmetry. As a result, these “polar” waves may show the effect of optical rectification in nonlinear centrosymmetric media by generating light-induced dc electric polarization. At the same time, waves of this type, due to their unusual symmetry properties, can be used for detecting the direction and sign of a dc electric field applied to the medium. The prospects of application of polar waves to data recording and processing are discussed.     

Electron acceleration by net inverse bremsstrahlung of a laser wave in a uniform magnetic field and longitudinal electric waves

The nonzero net dc (ponderomotive force) acting on high-energy beam electrons due to net inverse bremsstrahlung (the absorption by inverse bremsstrahlung minus the emission by stimulated bremsstrahlung) of the electromagnetic wave in a uniform magnetic field and longitudinal electric waves is calculated by using quantum kinetics in accordance with the correspondence principle. It is found that the ponderomotive force can be far stronger than the Lorentz force of the laser wave for an electron-energy range far beyond the free electron lasing regime.     

DC column plasma kinetics in a longitudinal magnetic field

The cylindrical column plasma of a neon dc glow discharge under the influence of a weak longitudinal magnetic field is studied. An extended, fully self-consistent model of the column plasma has been used to determine the kinetic quantities of electrons, ions and excited atoms, the radial space charge field, and the axial electric field for given discharge conditions. The model includes a nonlocal kinetic treatment of the electrons by solving their spatially inhomogeneous kinetic equation, taking into account the radial space charge field and the axial magnetic field. The treatment is based on the two-term expansion of the velocity distribution and comprises the determination of its isotropic and anisotropic components in the axial, radial, and azimuthal direction. A transition from a distinctly nonlocal kinetic behavior of the electrons in the magnetic-field-free case to an almost local kinetic behavior has been found by increasing the magnetic field. The establishment of the electron cyclotron motion around the column axis increasingly restricts the radial electron energy transport and reduces the radial ambipolar current. The complex interaction of these transport phenomena with the alterations in the charge carrier production leads finally to a specific variation of the electric field components. The axial field increases by applying weak magnetic fields, however, decreases with increasingly higher magnetic fields. At higher magnetic fields, the radial space-charge field is considerably reduced     

电磁波在大面积等离子体片中传播特性的分析

脉冲磁约束线形空心阴极放电形成的大面积等离子体片可应用于等离子体天线、隐身及模拟超音速飞行器表面的等离子体鞘套. 本文首次利用实测等离子体片电子密度时空分布和横向场传播矩阵法, 研究了电磁波在等离子体片中反射率、透射率、吸收率随频率及脉冲放电时间的变化特征. 结果表明: 极化方向平行磁场的电磁波, 在小于截止频率的低频带内具有较高的反射率和吸收率, 增大电流, 反射率增加, 吸收率下降, 在大于截止频率的高频带内反射率和吸收率较低, 增大电流, 透射率下降, 吸收率升高; 极化方向垂直磁场的电磁波在高混杂谐振频率附近存在吸收率明显增强的吸收带, 谐振吸收峰值与放电电流无关; 脉冲放电期间, 电磁波的反射率、透射率与吸收率由不稳定过渡到稳定的时间约为100 μs, 过渡时间随着放电电流的增加而增大, 极化方向垂直磁场、小于截止频率的电磁波在稳定放电阶段谐振吸收较强. 本文的研究成果对利用等离子体片实现对电磁波的稳定高反射作用具有重要意义.