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An analytical model is presented, which calculates recombination radiation in He and Ly characteristic plasma lines formed as a result of irradiating a solid target with an intense picosecond laser pulse. For calibration, this model is compared with the computer FLYCHK code. According to the results of the comparison, the region of the model applicability lies in the temperature range of the main plasma volume of 200–2000 eV and the electron density of 1023–1024 cm–3. The advantage of this analytical model is its simplicity, which makes it possible to be used for quick estimates of the luminosity of the characteristic plasma lines at a given temperature and density, or, vice versa, to determine the density and temperature of a plasma source from the relative height and structure of the emitted lines.

The dependence of energy of an ion accelerated from a thin laser target on its charge is investigated numerically and analytically. It is demonstrated that this dependence is determined by the values of ionization potentials of the target atoms and has a sharper character than those obtained in previous models of ion acceleration. The physical origin of sharper dependence is the relation of ion charge to its initial position in the ionized target. As a result, more highly charged ions turn out to be in the region of stronger accelerating field and thus attain higher energy. For a laser target made of a gold foil, the results obtained with an analytical model are compared to those obtained by means of a two-dimensional simulation, which demonstrated agreement between theoretical and calculated dependences of ion energy on its charge.

A mathematical model of proton image formation is developed, and minimum size of objects visible under proton irradiation (resolution of proton radiography) is estimated. Due to ion flux being laminar, micron-sized objects smaller than the ion emission spot size are detected. The results of simulation are in good agreement with the experiment.

The possibility of improving the efficiency of X-ray generation under the interaction of femtosecond laser pulses (exhibiting high repetition rate and subrelativistic intensity) with a thin copper foil by changing the angle of incidence of the laser radiation is studied both experimentally and theoretically. The brightness of such an X-ray source in the conducted experiments considerably exceeded that of a conventional X-ray tube. The structure of the target surface before and after interaction is described in detail, and specific features of the influence of this structure on absorption of laser pulses are analyzed.

The set of equations describing the motion of a thin (compared to the wavelength) target in the field of a laser pulse that takes into consideration separate motion of the electron and ion layers is derived. In the case of strong Coulomb coupling between the layers, the set of equation of motions of the layers is reduced to the well-known light-sail equation containing a self-consistent coefficient of nonlinear reflection of laser radiation by a moving target. The optimal thickness of the laser target at which the target acquires maximum energy for given laser-pulse parameters is determined. It is shown that this thickness depends not only on laser intensity, but also on laser-pulse duration and the ratio of electron and ion masses. The growth rates of transverse instability of optimal targets under their intense acceleration are analyzed. It is demonstrated that instability does not develop in the currently experimentally accessible range of laser intensities and pulse durations between 100 and 200 fs.

Generation and propagation of fast electrons in laser targets consisting of thin nanofilaments are studied numerically and analytically. Such targets completely absorb laser radiation and exhibit a large coefficient of laser-energy conversion to kinetic energy of a flow of fast electrons. Analytical estimates show that the optimal thickness of the filament is on the order of the skin depth of the laser plasma, while an optimal distance between filaments is on the order of the Debye radius of hot electrons. A bunch of relativistic electrons can propagate as far as several hundred micrometers in such targets, while the fastest electrons can propagate several millimeters. Upon bending of filaments, the flow of electrons propagates along the filaments and can be focused by bringing the filaments together. Laser targets of the discussed composition are used as sources of dense bunches of relativistic electrons and subsequent generation of high-intensity X-ray radiation with their help.

We present the results of experimental studies of the parameters of scattered radiation of a photo-dissociation iodine laser that is focused in a line onto a flat target made of germanium or zinc. At laser radiation intensities above 1013 W/cm2, an anomalously strong scattering in the direction of the line is observed in the form of narrow beams with a divergence of 5–10 mrad. In this case, the scattered energy is estimated to be 70–120 J, which corresponds to 30–50% of the total energy of the laser beam. This scattered radiation appears only in the presence of a prepulse with an intensity of no lower than 1011 W/cm2 that is emitted ∼5 ns earlier than the main laser pulse. At lower intensities of the prepulse, no anomalous scattering of radiation is observed, which indicates that the preliminary action of the laser radiation on the target plays a decisive role in the scattering mechanism.

Based on numerical PIC modeling and an analytical model, we analyze the interaction of a short high-intensity laser pulse with homo- and heterogeneous (two-layer) shell targets. We show that the shell target is capable of focusing ions in a narrow region. In this case, the ion energy exceeds the ion energy for a flat infinite target of the same thickness. We propose to use the effect of focusing and cumulation of ions to implement the collision of ionic beams that counterpropagate from opposite sides of the sphere and to increase the yield of ion-ion reactions. The constructed model makes it possible to calculate the energy of the ion and the number of ions in the region of focusing.

We have constructed a two-phase analytical model of acceleration of ions in a two-layer laser target. The first phase of acceleration is isothermic and covers the action time of the laser pulse, while the second phase is adiabatic and occurs after the end of the laser pulse. The maximal ion energy is obtained as a function of parameters of the laser pulse and target. We compare analytical results with PIC calculations and show that the theory is adequate.

An analytical model of Kα radiation of thin laser targets has been developed. It has been shown that, for such targets, the motion of fast electrons is significant not only in the target itself but also in vacuum. The considered dependences for the free path length of a fast electron and for the absorption coefficient of laser radiation on the laser intensity with allowance for the electron motion in vacuum make it possible to match the results of the proposed model with the experimental data on generation of Kα radiation in wide ranges of laser intensities (1018–1021 W/cm2) and thicknesses (1–100 μm) of targets.

Experimental results on the generation of terahertz (THz) electromagnetic radiation under ionization of air by femtosecond pulses at fundamental and second-harmonic frequencies of a Ti-sapphire laser are presented. The mean power of the generated THz radiation as a function of the time delay between two pulses of different frequencies is found to be quasi-periodical. Theoretically, we show that efficient generation of THz radiation is governed by the inertial part of the nonlinear response of the medium, which is determined by the dynamics of population of highly excited states with subsequent emission of electrons.

The interaction of an intense circularly polarized laser pulse with a layer of plasma of supercritical density is studied. The nonlinear skin effect for the electromagnetic field and the coefficient of collisionless absorption of the laser pulse were calculated analytically. It is shown that, in the process of interaction with the plasma, the laser pulse generates solitons propagating through the plasma layer and transferring the radiation through the opaque medium. The coefficient of transparency of the plasma layer for the soliton-like penetration of the laser radiation was calculated. The plasma parameters at which the collisionless absorption is small as compared to the transformation of the laser energy into solitons were found.

The results of experimental measurement and analytical estimation of the coefficient of backward reflection from targets made of various materials upon their irradiation by a picosecond laser pulse having the intensity of (0.8–4) × 1018 W/cm2 are presented. It is shown that the induced surface instability leads to the formation of a profile backscattering the incident radiation. The coefficient of backward reflection achieves a few percent and has an intensity optimum depending on the target material.

The diffraction efficiency and the resistance to radiation damage of gratings with a multilayer dielectric coating, which are used for compression of high-power laser pulses, are studied. The effect of smoothing of the profile of the metallized surface of the grating upon deposition of dielectric coatings on the energy characteristics of the grating at the wavelength λ=1.05 μm is analyzed. Gratings with various profiles of the metallic surface relief and with different contrast of the refractive indices of the dielectrics forming the coating are considered.