[en] Generation of ultra-intense laser pulses is very important for a number of scientific and technical applications, such as the fast ignition (FI) scheme for in the inertial confinement fusion (ICF), the plasma accelerators, etc. The chirped pulse amplification is the actual technique to reach maximum peak power at a given energy. The pulse energy is then limited by the thermal damage of compression gratings, which for multi-kJ applications have to be very large and extremely expensive. There is another idea, which is based on non-linear pulse energy conversion. It does not require the pulse stretching or compression but considers the stimulated Brillouin and/or Raman scattering (SBS/SRS) in plasma. The use of plasma releases the problem of thermal and optical damage of the active media, but requires an efficient control of the dynamics of the stimulated scattering. We develop a model of a pulsating regime of the backward SBS at high laser intensities. This regime corresponds to the strong coupling between the scattered and ion acoustic wave and allows one to consider the pulse durations shorter than the ion acoustic wave period. The results of the theoretical model are compared with the 2D electromagnetic paraxial code and the full PIC 1D code. We explore the optical conditions for generating ultrahigh laser peak power. By using a gas jet or exploding foil plasma of 10% of the critical density, one may expect to achieve an efficient compression of a 1 ns 40 KJ laser pulse down to a few ps at the length of a few mm. We will present the analysis how the plasma density and flow velocity, the noise level and the profile of the Stokes prepulse affect the pulse compression characteristics and the conversion efficiency. (Author)

[en] Recent experiments demonstrate an efficient acceleration of protons and heavier ion species in the interaction of relativistically intense laser pulses with thin solid foils. These energetic particles are originating from the target surface where the density gradient is extremely steep and the electrostatic field attains to very large values. However the details of the acceleration mechanisms are not well understood. In this talk I will discuss the physical processes, which take place in plasma set in expansion by a minority of highly energetic electrons. The expansion is in a form of a collisionless, electrostatic shock waver, its position and amplitude control the number and the energy spectrum of accelerated protons. the energy re partition between the protons and other ion species depends strongly on the target composition, the hot electron spectrum, and the shock wave structure. Simple analytical models will be compared with the hybrid numerical simulations where the ions are described kinetically and the electrons assure the charge neutralization and with the PIC simulations where all species are treated kinetically. (Author)

[en] Hot electrons and hard x-ray pulses produced by the interaction of strong laser radiation with an underplasma is analytically and numrically investigated. The distribution function and parameters of the fast particles are determined, and the energy and spectrum of hard x%-ray pulses are calculated. (AIP)

[en] Current-voltage (I-V) characteristics of p-i-n structures based on amorphous silicon (α-Si:H) with small hole diffusion lengths (shorter than the thickness of the i-layer of a p-i-n structure) have been experimentally studied with and without illumination. It is shown that forward I-V characteristics of structures of this kind can be described by a dependence inherent in diodes, with a diode ideality factor two-three times the maximum value of 2, theoretically predicted for generation-recombination currents in p-n junctions. The dark current is always substantially lower than the photocurrent in a cell biased with a voltage approximately equal to the opencircuit voltage of the photocell. Dark currents cannot contribute to the I-V characteristic under illumination. The photocurrent decreases with increasing photovoltage at a bias lower than the open-circuit voltage because of a decrease in the collection coefficient and the increasingly important role of back diffusion of electrons into the p-contact, rather than as a result of the dark injection. In the case of biases exceeding the open-circuit voltage, back diffusion becomes the predominant component of the current.

[en] Numerical simulations were made of the interaction of a relativistically intense laser pulse with a target consisting of nanometre fibres. Fast electrons were shown to execute forced betatron oscillations in the electrostatic fibre field and the laser field. The fibre diameter was determined whereby the amplitude of betatron electron oscillations is resonantly increased. The power of coherent X-ray betatron radiation of the electron bunch was calculated outside of the resonance domain and in the resonance case. We showed that the laser-to-X-ray betatron radiation conversion coefficient in the resonance case amounts to a few percent and the target made up of nanometre fibres may be regarded as an efficient laser-driven source of coherent X- and gamma-ray radiation. (interaction of laser radiation with matter. laser plasma)

[en] The intensity of K_α radiation emanating from transversely limited thin laser targets with a periodic relief superposed onto its front side was calculated. The relief parameters and the geometrical target dimensions were optimised with the help of an analytic model. The optimal target was shown to possess a nearly 100% absorption coefficient for laser radiation and a high (up to 10^-3) coefficient of laser radiation conversion to the X-ray K_α radiation. (interaction of laser radiation with matter. laser plasma)

[en] A technique for in situ fabrication of aluminum-based Ohmic contacts to EuO by molecular-beam epitaxy is proposed. These contacts have a linear current–voltage curve and a contact resistance of 0.55 Ω mm and are stable in air. This suggests that the proposed technique holds promise for spintronic applications.

[en] We study the motion of an electron and emission of electromagnetic waves by an electron in the field of a relativistically intense laser pulse. The dynamics of the electron is described by the Newton equation with the Lorentz force in the right-hand side. It is shown that the electrons may be ejected from the interaction region with high energy. The energy spectrum of these electrons and the technique of using the spectrum to assess the maximal intensity in the focus are analysed. It is found that electromagnetic radiation of an electron moving in an intense laser field occurs within a small angle around the direction of the electron trajectory tangent. The tangent quickly changes its direction in space; therefore, electromagnetic radiation of the electron in the far-field zone in a certain direction in the vicinity of the tangent is a short pulse with a duration as short as zeptoseconds. The calculation of the temporary and spectral distribution of the radiation field is carried out. (superintense laser fields)

[en] 3C-SiC films grown on Si (100) substrates by CVD method using silane-propane- hydrogen system were analyzed for crystallinity at various process pressures. The deposition experiments were carried out in a shower-head type cold-wall CVD reactor. The influence of growth conditions on a structural modification of experimental samples was studied by X-ray diffraction (XRD) measurements, Fourier transform infrared spectroscopy (FTIR) and spectroscopic ellipsometry (SE)

[en] The nonlinear behavior of the I–V characteristics of symmetric contacts between a metal and degenerate n-GaN, which form oppositely connected Schottky diodes, is investigated at free-carrier densities from 1.5 × 10¹⁹ to 2.0 × 10²⁰ cm^–3 in GaN. It is demonstrated that, at an electron density of 2.0 × 10²⁰ cm^–3, the conductivity between metal (chromium) and GaN is implemented via electron tunneling and the resistivity of the Cr–GaN contact is 0.05 Ω mm. A method for determining the parameters of potential barriers from the I–V characteristics of symmetric opposite contacts is developed. The effect of pronounced nonuniformity of the current density and voltage distributions over the contact area at low contact resistivity is taken into account. The potential-barrier height for Cr–n⁺-GaN contacts is found to be 0.47 ± 0.04 eV.