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The spectral-angular distribution of an induced X-ray parametric quasi-Cerenkov radiation (PXR), generated by a relativistic particle in periodic structures, is derived for different diffraction geometries. The possibility of experimental observation of such radiation is discussed. [Russian Text Ignored].

A mechanism of stimulated emission of electromagnetic radiation by an electron beam in carbon nanotubes is theoretically considered. Three basic properties of carbon nanotubes: a strong slowing down of surface electromagnetic waves, ballisticity of the electron motion over typical nanotube length, and extremely high electron current density reachable in nanotubes, allow proposition of them as candidates for the development of nanoscale Cherenkov-type emitters, analogous to traveling-wave tube and free electron laser. Dispersion equations of the electron-beam instability and the threshold conditions of the stimulated emission have been derived and analyzed, demonstrating realizability of the nanotube-based nano-free electron lasers at realistic parameters of nanotubes and electronic beams.

The free electron laser on the basis of parametric (quasi-Cerenkov) instability is considered. Threshold conditions for this process are obtained. It is shown that rather rigid requirements for the particle beam are needed in the X-ray region.

Basic mechanisms of the interaction of electron beam tavelling through a carbon nanotube with electromagnetic wave, resulting in the radiative instability and generation of stimulated radiation, are considered. The effect of the surface electromagnetic wave slow-down in CNT (c/v > 100) [Slepyan et al., Phys. Rev. B 60, 17136, 1999] is exploited to synchronize the wave and the beam and thus to realize the Cherenkov radiation mechanism. Alternative mechanism of the electron beam instability is proposed based on the undulator emission arising due to the interband transitions of electrons moving in nanotube. The dispersion equations of the electron beam instability and threshold conditions for the stimulated radiation are derived and studied. The analysis of the threshold conditions estimates the possibility of the stimulated emission by electron beam as realistic and attainable at present-day experimental technique.

This contribution is devoted to investigation of multiwave Volume Free Electron Laser (VFEL) by methods of mathematical modelling. Special emphasis is placed on consideration of three‐wave VFEL. Mathematical modelling carried out confirmed some preliminary physical estimates. Computer code VOLC for simulation of different schemes of two‐ and three‐wave VFEL is described. Key words: free electron laser, quasi‐Cherenkov instability, simulation, nonlinear integro‐differential system. First Published Online: 14 Oct 2010

This report is devoted to the application of external Bragg reflectors in operating a volume parametric X-ray FEL. It is shown that external Bragg reflectors permit not only a reduction in electromagnetic energy losses through target boundaries but also a reduction in the radiation self-absorption inside the target by modifying radiation modes excited in the active medium containing a particle beam plus a crystal. As a result, the starting beam current can be reduced by more than a factor of ten. It is also shown that the best conditions for lasing are realized when the diffracted wave is reflected by the external Bragg reflector.

New possibilities of frequency tuning in vacuum electronic devices are considered by the example of volume free electron laser. Recent experimental results are presented along with some theoretical comments and technical proposals. Experimental study of dependence of radiation frequency and intensity on change of the angular orientation of grooves of diffraction gratings with respect to electron beam velocity due rotation of diffraction gratings is presented. Two geometries of diffraction are analyzed: those of Bragg and Laue. Change of lasing efficiency with grating rotation is considered. VFEL generator is proposed as a new type of tunable backward wave tube with variable period (due to gratings rotation) and VFEL amplifier is considered as a new type of tunable traveling wave tube.

The parametric quasi-Cherenkov free electron laser is studied in a surface diffraction geometry. It is shown that the application of the quasi-Cherenkov radiation mechanism makes it possible to realize the generation of wavelengths in the 0.1–10 A region with a current density j ∼ 10 8 A/cm 2 , in spite of the strong requirements on the electron beam quality. The possibility of production of stimulated quasi-Cherenkov radiation in different spectral ranges is investigated.

We have considered the structure of the fundamental symmetry violating part of the photon refractive index in vacuum in the presence of constant electric and magnetic fields. This part of the refractive index can, in principle, contain CPT symmetry breaking terms. Some of the terms violate Lorentz invariance, whereas the others violate locality and causality. Estimates of these effects, using laser experiments are considered., 12 pages

Use of non one-dimensional distributed feedback in VFEL gives possibility of frequency tuning in wide range. In present work dependence of lasing process on the angle between resonant diffraction grating grooves and direction of electron beam velocity is discussed., LaTeX, 9 eps figures, to be presented at FEL2002 Conference

For the omega-hyperon passing through matter the phenomena of spin rotation and oscillation has investigated quantitatively. Connection of these phenomena with constituent quark rescattering has been determined. It allows one to investigate quark rescattering directly without background of a single scattering., LaTeX, 21 pages with 4 figures, uses ioplppt.sty, iopl12.sty. Model of the inelastic corrections replaced

Surface plasmon-polariton waves with low-phase speed in carbon nanostructures can be utilized for the generation of coherent terahertz radiation through the Čerenkov mechanism, the effect being especially pronounced in bilayer and multilayer graphene. Using the many-body formalism and the tight-binding approach, we derived the dispersion equations of the surface plasmon-polariton waves in graphene. In single-layer graphene, the phase speed is about three to five times smaller than the speed of light in a vacuum. In bilayer graphene, inter-layer electron tunneling suppresses the reduction of the phase speed. Reduction of the phase speed by as much as 300 times is possible in a graphene structure with two spatially expanded monolayers, because inter-layer tunneling is suppressed, and the interlayer distance can be used to tune the plasmon frequency and the phase speed. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE)

We investigated several proposals utilizing the unique electronic properties of carbon nanotubes (CNTs) for a broad range of applications to THz optoelectronics, including THz generation by Cerenkov-type emitters based on carbon nanotubes and by hot electrons in quasimetallic nanotubes, frequency multiplication in chiral-nanotube-based superlattices controlled by a transverse electric field, and THz radiation detection and emission by armchair nanotubes in a strong magnetic field. Dispersion equations of the electron beam instability and the threshold conditions of the stimulated emission have been derived and analyzed, demonstrating realizability of the nanotube-based nanoFEL at realistic parameters of nanotubes and electronic beams.

The ability of thin conductive films, including graphene, pyrolytic carbon (PyC), graphitic PyC (GrPyC), graphene with graphitic islands (GrI), glassy carbon (GC) and sandwich structures made of all these materials separated by polymer slabs to absorb electromagnetic radiation in microwave-THz frequency range is discussed. The main physical principles making a basis for high absorption ability of these heterostructures are explained both in the language of electromagnetic theory and using representation of equivalent electrical circuits. The ideas of using carbonaceous thin films as the main working elements of passive radiofrequency (RF) devices, such as shields, filters, polarizers, collimators, are proposed theoretically and proved experimentally. The important advantage of PyC, GrI, GrPyC, GC is that, in contrast to graphene, they can be either easily deposited onto a dielectric substrate or are strong enough to allow their transfer from the catalytic substrate without a shuttle polymer layer. This opens a new avenue towards the development of a scalable protocol for cost-efficient production of ultra- light electromagnetic shields that can be transferred to commercial applications. A robust design via Finite Element Method and Design of Experiment for RF devices based on carbon/graphene films and sandwiches is also discussed in the context of virtual prototyping.