Narrowly divergent high-energy electron beam is experimentally demonstrated during the interaction of terawatt Ti:Sa laser radiation with a nitrogen gas-cluster jet at gas pressure corresponding to the boundary of the condensation region. A collimated electron beam with an energy of up to 10 MeV and a divergence of 10 mrad at a plasma concentration of 1019 cm–3 is obtained. The use of nitrogen instead of argon or krypton significantly improves the spatial (divergence) and energy (charge and spectrum shape) properties of the generated electron beam. The formation of clusters in a supersonic jet is observed and their composition is thermodynamically analyzed.

Efficient laser-plasma line X-ray source was developed. X-ray generation was optimized by the laser pulse duration alteration and using the local helium blowing into the microplasma region on a copper target located in atmospheric conditions. Measured Kα x-ray flux of 2·107 ph/pulse/2π sr and conversion efficiency of 10-5 were achieved correspondingly. Keywords: femtosecond laser pulses, X-rays.

A universal technique is developed for the detection of high harmonics generated by relativistic and subrelativistic laser pulses irradiating a solid target. Features in the spectra of harmonics generated by a parametric mid-IR laser system and near-IR laser system based on chirped pulse amplification were analyzed. Experimental spectra of harmonics in the range up to 35 nm were recorded. They can be used as a source of coherent radiation in the extreme UV region.

Terahertz pulse generation from multiterawatt laser surface plasma near thick solid targets and thin foils has been studied. Pulses with energies up to 7 μJ were detected in the spectral region <3 THz in the direction of specular reflection from the surface of the CaF 2 target. The dependence of the terahertz pulse energy $${{W}_{{{\text{THz}}}}}$$ on the laser pulse intensity $$I_{L}^{\alpha }$$ can be approximated by the power function $${{W}_{{{\text{THz}}}}} \sim I_{L}^{\alpha }$$ . For a fixed laser pulse duration and variable energy the power index lies in the range $$\alpha \approx 1.5{-} 2.8$$ , while for a fixed energy and variable duration $$\alpha \approx 1$$ .

X-ray generation under interaction of relativistic laser pulses with krypton clusters has been studied. It is shown that the optimal focusing points for generating characteristic and hard bremsstrahlung are located in regions with different cluster concentrations inside the gas jet. A record (4.2 × 10–6) conversion efficiency of relativistic laser pulses into characteristic Kα (12.6 keV) has been achieved under interaction with large krypton clusters. The bremsstrahlung plasma temperature has been measured to be Te = 6 keV at an integral energy of the X-ray pulse of 3 × 109 keV/(4π pulse). The application of the designed source in time-resolved X-ray studies and in radiobiology are discussed.

It is shown experimentally that the intensities of characteristic X-rays, terahertz radiation, and the second optical harmonic from a copper foil irradiated by sub-relativistic femtosecond laser pulses increase simultaneously with decreasing foil thickness. The efficiency of the generation of X-rays and terahertz radiation, as well as the 3/2 harmonic with a various degree of nonlinearity, depends on the intensity of radiation and the duration of a laser pulse. the behavior of measured signals is determined by the instability of the two-plasmon decay, by hot electrons, and by their circulation in observed processes.

The possibility of fabricating a flexible extended terahertz waveguide with low losses, which has a hollow core and a reflective shell of eight polypropylene capillaries placed in a common shell with an outer diameter of 7.5 mm, has been demonstrated. The passage of terahertz pulses with frequencies of 2.3–2.8THz through a waveguide (including a twisted one, Rbent ∼60 cm) longer than 3 m with an attenuation of 5 dB/m has been experimentally confirmed.

We obtained the spectra of high optical harmonics produced by subrelativistic femtosecond pulses on the surface of polystyrene, CaF 2 , BK7, and Al solid targets. High harmonics of up to the 51st order of radiation with central 3.85 µm wavelength were observed. The highest order harmonics were generated from the polystyrene target surface. The harmonics energy versus their numbers is shown to fit well a decaying power law with the exponent ranging from 4 to 8/3.

Terawatt laser pulses obtained after temporal compression due to nonlinear spectrum broadening in thin glass plates with subsequent dispersion compensation by chirped mirrors are experimentally characterized by spatially encoded spectral phase interferometry. The proposed method allowed to reconstruct the spectral and temporal phase of obtained 16 fs laser pulses with up to 20 mJ of energy in a single-shot mode with spatial resolution.

We obtained the spectra of high optical harmonics produced by subrelativistic femtosecond pulses on the surface of polystyrene, CaF2, BK7, and Al solid targets. High harmonics of up to the 51st order of radiation with central 3.85 µm wavelength were observed. The highest order harmonics were generated from the polystyrene target surface. The harmonics energy versus their numbers is shown to fit well a decaying power law with the exponent ranging from 4 to 8/3.

The dependence of the visible spectrum (harmonics 2 and 3/2) and the output of Cu K-alpha X-ray radiation on the energy and duration of subrelativistic intensity femtosecond laser pulse acting on a copper foil is investigated. It was found that for secondary radiation, the determining factor is the energy density, and not the intensity and duration of the pulse. The power-law dependencies of the secondary output radiation on the duration and the pulse energy have a significantly different indicator. The tendencies of changing the shape of the spectrum for regions dominated by various mechanisms of plasma heating are revealed.

Efficient laser-plasma line X-ray source was developed. X-ray generation was optimized by the laser pulse duration alteration and using the local helium blowing into the microplasma region on a copper target located in atmospheric conditions. Measured Кα x-ray flux of 2 •10^7 ph/pulse/2π sr and conversion efficiency of 10^-5 were achieved correspondingly.

Electric-current transients driven by high-peak-power midinfrared laser pulses are shown to provide a source of broadband current, wide-angle microwave-terahertz radiation, whose spectral, spatial, and polarization properties can be adequately understood from a perspective of impulsively driven antenna radiation. When suitably tailored, such laser-driven antennas are shown to generate bright microwave-terahertz pulses with energies in the range of tens of microjoules and ultrawide-angle radiation patterns extending to obtuse angles well beyond the broadside plane, with a considerable radiation flux detected at angles 0 > 125 degrees relative to the direction of the driver beam. Polarization of microwave radiation from laser-driven plasmas is shown to bear clear signatures of the symmetry of transient plasma currents, providing a sensitive probe for ultrafast laser-plasma interactions.

We demonstrate a multicompartment, power-scalable beam-line design in which sub-40-fs, terawatt field waveforms are tailored in space and time for downstream pulse compression to few-cycle pulse widths attained right at the site where the intense laser field interacts with a target. An accurate field-waveform characterization performed at multiple locations along the beam path shows that, despite all the complexity of their upstream nonlinear electrodynamics, field waveforms shorter than three field cycles can be delivered to a laser–matter interaction site in such a system, enabling a vast class of ultrafast strong-field laser–matter interaction studies.

Currently, the Kurchatov Laser−Synchrotron Complex is conducting research on the interaction of powerful femtosecond laser radiation with matter. The purpose of these studies is to develop new techniques and approaches for the characterization of high−temperature plasma, X−rays and particle acceleration, which can be the basis for the work planned within the framework of the synchrotron−neutron project. Laser−driven X−ray production, electron acceleration, nuclear fusion, ultrafast structural dynamics of nanoparticles in intense laser fields remains an active research topic, aimed at generating advanced controllable sources.

The laser-synchrotron facility (LSF) of the National Research Centre “Kurchatov Institute” (NRC KI) is a unique research complex that combines unprecedented possibilities of a cutting-edge rapidly developing field of modern science—physics of ultrashort laser pulses and superstrong electromagnetic fields, which provides unique diagnostic possibilities of the specialized synchrotron radiation (SR) source. The studies devoted to generation of superstrong light fields and interaction of these fields with a material, which had been performed at the LSF of the NRC KI in the last few years, are reviewed. An arsenal of diagnostic methods and the principles of locking of the SR source and the subpetawatt laser complex were developed, which makes it possible to solve the problems related to the dynamics of material structural transformation with extremely small temporal (picosecond) and spatial (atomic) resolution, to obtain knowledge on ultrafast temporal dynamics of chemical processes and control of chemical reactions, to study the interaction of X rays and high-energy particles with biological objects, to simulate experiments on the X-ray free-electron laser (XFEL), and to develop ideological platforms for participation of Russian scientists in the XFEL projects.

2-10 TW laser pulses are converted into THz range with relatively high efficiency in two schemes: large aperture thin nonlinear crystals (LiNbO 3 and GaSe) and low pressure, two-color gas discharge. 2–10 uJ energy pulse in THz range is obtained with tunable bandwidth up to 6 THz. Advantages of phase matched and non-matched THz generation near the breakdown threshold of thin crystals are discussed.