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.     

Influence of a magnetic field on the mutual rectification of alternating currents induced by electromagnetic waves in graphene

The direct component of the electric current induced in graphene placed in a constant magnetic field has been found in the case where two electromagnetic waves with two mutually perpendicular planes of polarization are normally incident on the surface of the sample. It has been demonstrated that the direct component of the current along the direction of the electric field vector of the wave with the frequency ω₁ arises only when the ratio between the frequencies of the incident waves is ω₁/ω₂ = 2 or 1/2. In the latter case, the direct current component appears only in the presence of a magnetic field.     

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.     

一种适于1维磁等离子体电磁波传输特性的FDTD分析

 提出了一个新的分析各向异性磁等离子体中电磁波传输特性的时域有限差分（FDTD）方法。该方法是将电流密度矢量与电场强度矢量之间的本构方程基于拉普拉斯变换原理转到复频域,然后再逆变换到时域得到它们之间显式的方程,最后再结合指数差分,得到离散时域的显式的FDTD迭代方程,解决了本构方程中电流密度矢量的分量相互耦合而不易直接离散的困难。该方法在数学上具有简单明了和易于计算的特点,同时通过该方法计算各向异性等离子体板的电磁波反射和透射系数,与其解析解进行比较,结果表明了该方法的准确性和有效性。     

基于动理论模型的一维等离子体电磁波传输特性分析

本文采用了动理论模型对电磁波在等离子体中的传播特性进行了研究.建立了与该模型相关的麦克斯韦-玻尔兹曼(MB)方程组,并采用FDTD方法加以求解,得到了等离子体区域内的粒子分布函数及空间中的电场分布.此外,本文还计算了电磁波入射到等离子体平板上的反射及透射系数,并将数值计算结果与解析解结果进行了比较,验证了该方法的正确性.     

Coefficients of diffusion and conductivity of semiconductor carbon nanotubes in an external electric field

The coefficients of electron diffusion and conductivity have been calculated for single-layer semiconducting carbon nanotubes in an external electric field with the strength vector directed along the nanotube axis. The evolution of the electronic system of the nanotubes has been described using the Boltzmann kinetic equation in terms of the quasi-classical approximation of relaxation time. An analytical expression of the electron diffusion coefficient has been obtained, and its nonlinear field dependence has been revealed.     

Generation of high harmonics by an alternating electric field in superlattices based on graphene

The conductivity of a superlattice based on graphene in an alternating electric field with a vector of intensity directed along the axis of the superlattice is described. The electronic system is described in terms of the kinetic Boltzmann equation in approximation of a constant time of relaxation. Nonlinear responses to the applied harmonic field are calculated and analyzed.     

Beams of electromagnetic radiation carrying angular momentum: The Riemann-Silberstein vector and the classical-quantum correspondence

All beams of electromagnetic radiation are made of photons. Therefore, it is important to find a precise relationship between the classical properties of the beam and the quantum characteristics of the photons that make a particular beam. It is shown that this relationship is best expressed in terms of the Riemann-Silberstein vector - a complex combination of the electric and magnetic field vectors - that plays the role of the photon wave function. The Whittaker representation of this vector in terms of a single complex function satisfying the wave equation greatly simplifies the analysis. Bessel beams, exact Laguerre-Gauss beams, and other related beams of electromagnetic radiation can be described in a unified fashion. The appropriate photon quantum numbers for these beams are identified. Special emphasis is put on the angular momentum of a single photon and its connection with the angular momentum of the beam.     

Nonlinear propagation of vector extremely short pulses in a medium of symmetric and asymmetric molecules

The nonlinear propagation of extremely short electromagnetic pulses in a medium of symmetric and asymmetric molecules placed in static magnetic and electric fields is theoretically studied. Asymmetric molecules differ in that they have nonzero permanent dipole moments in stationary quantum states. A system of wave equations is derived for the ordinary and extraordinary components of pulses. It is shown that this system can be reduced in some cases to a system of coupled Ostrovsky equations and to the equation intagrable by the method for an inverse scattering transformation, including the vector version of the Ostrovsky–Vakhnenko equation. Different types of solutions of this system are considered. Only solutions representing the superposition of periodic solutions are single-valued, whereas soliton and breather solutions are multivalued.     

A lattice of electromagnetic solitons in a superlattice formed by a system of quantum dots

Considering the Maxwell equations for the electromagnetic-field propagation in a solid with a three-dimensional superlattice of quantum dots linked by strong tunneling along one axis, we obtained a phenomenological equation in the form of the classical 2+1-dimensional sine-Gordon equation. Electrons were considered classically in the formalism of the Boltzmann kinetic equation for the distribution function. Solutions were obtained as a soliton lattice for the vector potential of the electric field. These lattices emerge as a consequence of the coherent change of the classical distribution function and the electric field generated by tunneling electrons in a system of quantum wells.     

On the Effective Metric for an Electromagnetic Wave Propagating in the Field of an Intense Laser Radiation

It is shown that in the nonlinear electrodynamics of vacuum, which is a corollary of quantum electrodynamics, a weak electromagnetic wave propagates in the field of an intense laser radiation as if this took place in some effective space-time whose metric tensor depends on the electric field of the laser radiation. The components of the metric vector of the effective space-time along the geodesic lines of which the rays of the weak electromagnetic wave propagate in the given case have been found. It is pointed out that this property may serve as a basis for observing the manifestations of the nonlinearity of the electrodynamics of vacuum.     

Equivalent representation of orthogonal-field electrodynamics by system of covariant lines of force

It is shown that the electrodynamics of orthogonal magnetic and electric fields can be represented as the dynamics of covariant lines of force. Such a representation is provided for the Lienard-Wichert field of an arbitrary moving charge and the field of a charge that moves uniformly about a circle. The four vector of the electric lines of force is written as the sum of the four vector of the charge and the radius four vector directed along the light cone to the observation point. This vector is a solution of an equation that formally coincides with the equation of motion of the magnetic moment in external fields for a zero intrinsic magnetic moment. The electromagnetic field is reconstructed according to a system of lines that correspond to the total equation of motion of the magnetic moment. Such a field for a uniformly circulating charge is examined.Erevan Physics Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, Nos. 3, 4, pp. 313–323, March–April, 1992.     

Multiphoton intraband absorption of electromagnetic waves and stimulated scattering by optical phonons in the superlattice

Multiphoton intraminiband absorption of the electromagnetic wave and stimulated scattering by optical phonons in the semiconductor superlattice are considered. The absorption coefficient is found without using the quantum kinetic equation. The absorbed energy is plotted versus the electric field of the wave. It is found that, as the electric field grows, the absorbed energy reaches a maximum and then starts decreasing in an oscillatory manner. An explanation for such a run of the absorbed energy with electric field is given. It is shown that multiphoton absorption must be taken into account if the condition eEd ≥ ?ω is satisfied. Stimulated multiphoton scattering by optical phonons in superlattices is shown to produce harmonics of the scattered light at frequencies both higher and lower than those of the incident light. Scattering partial cross sections are found and plotted versus the incident wave intensity.     

The Franz-Keldysh effect in superlattices in the field of a nonlinear electromagnetic wave

We study the effect of interminiband breakdown in a semiconductor quantum superlattice in a constant electric field and in the field of a nonlinear wave whose intensities are directed along the superlattice axis. The problem has been solved in the quasiclassical approximation for an arbitrary ratio between the widths of the allowed and forbidden minibands. In particular cases, we have obtained formulas for the breakdown probability in the presence of only one field, as well as for a linear wave and a solitary wave (soliton). It is shown that the probability of interminiband breakdown increases with the nonlinearity parameter of the electromagnetic wave k. The absorption coefficient of the nonlinear wave is calculated for typical parameters of the superlattice. Pedagogical University, Volgograd, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 6, pp. 758–766, June, 1998.     

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.     

Nonlinear diffraction of super-gaussian laser beams in an array of quantum-dot chains with coulomb interaction taken into account

We consider the propagation of super-Gaussian monochromatic laser beams in a three-dimensional array of quantum dots coupled by the tunneling effect along one axis. The electron energy spectrum of the system corresponds to the Hubbard model, where the Coulomb interaction of electrons in quantum dots is taken into account. The field of the laser beam is described by the Maxwell equations, from which a nonhomogeneous wave equation for the vector potential is obtained. In the approximation of slowly varying amplitudes and phases, the wave equation is reduced to a phenomenological equation describing the electromagnetic field in an array of chains of quantum dots. We study the influence of the system parameters and the frequency of the laser-beam field on the propagation in the medium by solving numerically the phenomenological equation. We obtain the dependence of the factor characterizing the diffraction blooming of the beam in an array of chains of quantum dots on the parameters of the system’s electron energy spectrum.     

Effect of the field of a nonlinear electromagnetic wave on the shape of a soliton in a semiconductor superlattice

The effect of the electric component of the field of a high-frequency (HF) nonlinear electromagnetic (EM) wave on the propagation of a solitary EM wave (soliton) in a quantum semiconductor superlattice is studied. It is noted that in the collisionless approximation, the solution of the modified sine-Gordon equation corresponding to the amplification of an EM pulse that, with allowance made for interminiband electron transitions, transforms into a dissipative soliton is possible. The effect of electron collisions with irregularities of the crystal lattice on the soliton dynamics under the action of the field of a HF nonlinear wave is considered. The condition for an increase in the traveling time of the solitary wave is found.