Interaction of space-charge waves in an electron beam with electromagnetic waves in a longitudinal magnetic field

The effect of space charge on the interaction between an electron beam and an electromagnetic wave in a longitudinal magnetic field has been considered. The equations describing the interaction processes have been formulated within the two-dimensional linear theory and solved using the dispersion-equation approach and the successive approximation method.     

Quantum modulation of an electron beam in the field of opposite electromagnetic waves

The quantum modulation of an electron beam in the field of opposite electromagnetic waves, at a frequency equal to the difference of the wave frequencies, and its harmonics, is obtained. The depth of the modulation becomes of order one at relatively small intensities of the laser fields (including a real spreading of the beam). In the case of equal frequencies of the waves (when the Kapitza-Dirac effect occurs particles form a beam. An experiment for obtaining a modulated beam of particles at the frequencies of the laser radiation, and its harmonics, as well as for bunching of particles in the field of a standing wave is suggested.     

Enhanced transmission of electromagnetic waves through metamaterials

This paper reviews our recent experimental and simulation results regarding the electromagnetic wave transmission through three configurations of sandwiching structures of metamaterials: a metallic mesh sandwiched between two identical layers composed of split rings, metallic fractals, and fractal slits, respectively. We observed the enhanced transmission of the waves through these three types of sandwiching composites with respect to the opaque metallic mesh. The locations of the transmission peaks in the spectrum are associated closely with the band characteristics of the sandwiching layer by appearing either on the left- or the right-hand side of its band. PACS 41.20.Jb; 42.70.Qs; 78.20.-e; 42.25.Bs; 47.53.+n     

Manipulating electromagnetic waves with metamaterials: Concept and microwave realizations

Our recent efforts in manipulating electromagnetic （EM） waves using metamaterials （MTMs） are reviewed with em- phasis on 1） manipulating wave polarization and transporting properties using homogeneous MTMs, 2） manipulating surface-wave properties using plasmonic MTMs, and 3） bridging propagating and surface waves using inhomogeneous meta-surfaces. For all these topics, we first illustrate the physical concepts and then present several typical practical real- izations and applications in the microwave regime.     

Interaction of surface acoustic waves with moving vortex structures in superconducting films

A method is proposed for describing a moving film vortex structure and its interaction with surface acoustic waves. It is shown that the moving vortex structure can amplify (generate) surface acoustic waves. In contrast to a similar effect in semiconductor films, this effect can appear when the velocity of the vortex structure is much lower than the velocity of the surface acoustic waves. A unidirectional collective mode is shown to exist in the moving vortex structure. This mode gives rise to an acoustic analogue of the diode effect that is resonant in the velocity of the vortex structure. This acoustic effect is manifested as an anomalous attenuation of the surface acoustic waves in the direction of the vortex-structure motion and as the absence of this attenuation for the propagation in the opposite direction.     

Manipulating electromagnetic wave with the magnetic surface plasmon based metamaterials

In this work, we have investigated the optical properties of the magnetic metamaterials (MMs) consisting of periodically/randomly arranged ferrite rods. By calculating the photonic band diagrams and transmittance, we have identified a photonic band gap originating from the magnetic surface plasmon (MSP) resonance. In addition, by tuning the external magnetic field (EMF), an MM slab can be used as an optical switch. Our simulated results also suggest that the optical properties of the MMs are robust against the position disorder and the size fluctuation of the ferrite rods. Moreover, by examining the relation between the transmittance and the EMF, we can optimize the EMF to realize the best switching effect. With the retrieved effective constitutive parameters ε _eff and μ _eff obtained from the effective-medium theory, the optimal EMF can be understood in a more clear manner.     

Surface electromagnetic waves at the interface between two dielectric superlattices

The electrodynamic properties of the interface between two periodic dielectric superlattices are studied. It is shown that the interface may serve as a guide for an electromagnetic wave whose field decays exponentially on both sides of the plane of the interface. The field and power flux distributions, as well as the frequency dependence of the field penetration depth, are studied.     

The interference of an electron beam with the surface reaction between oxygen and germanium

Electron beam assisted adsorption and desorption of oxygen was studied by Auger electron spectroscopy (AES). Beam assisted adsorption was observed on clean as well as on oxidized surfaces. After an oxygen exposure of 1000 × 10^?7 Torr min and continuous irradiation with beam voltage of 1.5 kV and beam current density 2 microA mm^?2, the oxygen 510 eV signal amplitude from the point of beam impact was 2.5 times greater than the signal from the non-irradiated region. The Ge 89 eV signal showed a corresponding decrease. Enhanced adsorption occurred at beam energies as low as 16.5 eV. After irradiation, the oxidized surface was not carbon contaminated. Following an oxygen exposure of 30 min at 0.1 Torr and 550°C and subsequent additional beam assisted exposure of 1000 × 10^?7 Torr min, the maximum oxide thickness was about 18 Å. Beam assisted desorption did not occur from thin oxygen layers (0–510 eV signal strength less than 5 units, calculated oxide thickness about 6 Å), but occurred from thick oxides and stopped after the signal amplitude had decreased to 5 units. Based on these results, a model for the structure of the oxygen layer covering the Ge(111) surface is proposed. Mechanisms for adsorption and desorption are discussed. The implications of beam assisted adsorption and desorption on electron beam operated surface measurements (LEED, AES, ELS, APS etc.) are stressed.     

Excitation of surface and volume electromagnetic waves in left-handed media by an electron bunch

We study theoretically the Vavilov-Čerenkov radiation from a nonrelativistic electron bunch moving in free space over a left-handed medium. It is shown that in the frequency range in which the refractive index of the medium is negative, Vavilov-Čerenkov radiation leads to simultaneous excitation of volume and surface electromagnetic waves in the same frequency range. The wave vector of the surface wave in the plane of an interface of two media is greater in magnitude than the corresponding quantity for the volume wave. The energy fluxes of volume and surface waves in the left-handed medium are studied. The radiation pattern of the bunch is found. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 5, pp. 406–417, May 2007.