[en] The method is proposed for calculating the M² factor by using the averaged description of wave beams (the method of moments). The values of M² are calculated for the super-Gaussian intensity distribution with phase distortions caused by the electron and thermal self-focusing and spherical aberration. (laser beams)

[en] It is shown that the time shifts of the intensity maximum and B-integral for an amplified laser pulse are proportional to the energy extraction from the amplifier normalised to the saturation energy, the proportionality coefficient being equal approximately to 1/7 and 1/14 of the pulse duration, respectively. Simple analytic expressions are obtained for the maximum values of the output intensity and B-integral. The results are experimentally confirmed by amplification observed in a Nd:YLF crystal. (lasers. amplifiers)

[en] Photocathode electron guns are key to the generation of high-quality electron bunches, which are currently the primary source of electrons for linear electron accelerators. The photogun test bench built at the Joint Institute for Nuclear Research (JINR) is currently being used to further develop the hollow (backside irradiated) photocathode concept. A major achievement was the replacement of the hollow photocathode by a technologically more feasible transmission photocathode made from a metal mesh that serves as a substrate for films of various photomaterials. A number of thin-film cathodes on quartz glass substrates are fabricated by photolithography. The vectorial photoeffect (related to the surface-normal component of the wave electric field) is observed and found to significantly affect the quantum efficiency. The dependence of the quantum efficiency of diamond-like carbon photocathodes on the manufacturing technology is investigated. The Rutherford backscattering and elastic recoil detection techniques are combined to carry out an elemental analysis of the films. An estimate of the emittance of a 400 pC electron beam is obtained using the cross-section method. (conferences and symposia)

[en] Linearised equations for the amplitudes of harmonic perturbations of strong waves in quadratic and cubic nonlinear media are obtained within the model of plane monochromatic waves. The dependences of the gains of noise components of the first and second harmonic waves upon frequency doubling on the B integral are found. The maximally admissible noise level in the fundamental radiation beam is calculated by the example of a 0.5-mm-long KDP crystal at the peak intensity of 4.5 TW cm^-2. (nonlinear-optics phenomena)

[en] The effect of various technological factors like the direction of crystal growth [(100) or (101)], acidity of the mother solution, growth rate, degree of filtration of the mother solution, purity of the starting raw material, specially introduced impurity (Pb), as well as after-growth thermal annealing, on the optical breakdown threshold of KDP crystals grown by the technique of rapid growth of profiled crystals is studied. It is shown that by using initial high-purity salts and fine filtration of solutions followed by after-growth annealing, it is possible to increase the optical breakdown threshold of profiled rapidly grown KDP crystals to values corresponding to the requirements of modern laser designs. (laser devices and elements)

[en] A simple qualitative model of beams focused stimulated Brillouin scattering (SBS), capable of providing a sufficiently accurate description of the Stokes pulse profile, was developed. The characteristics of deformation of a laser pulse during amplification in two-pass and four-pass amplifiers with an SBS mirror were investigated theoretically and experimentally for fully overlapping pulses. The influence of pumping and spontaneous emission was ignored. Approximate formulas were derived for determination of the duration of an output pulse and of its leading edge. The parameters required for the most effective control of the output pulse profile were determined. (nonlinear optical phenomena and devices)

[en] We propose a method for laser pulse temporal shaping applying just an opaque solid 2D mask as a shaping element. The research is motivated by recent experimental data on temporal distortions produced in chirped picosecond pulses by spatial light modulators (SLMs) commonly used in shaping schemes and consequent demand for alternative solutions.

In the presented scheme, the effect of grey-level masking in the spectral domain is achieved by dimensional reduction from 2D shaping on air to 1D obtained modulation at the fiber output. The mask is placed in the Fourier plane of a compressor with zero frequency dispersion. Instead of a spherical telescope in the compressor, a cylindrical one is used. Due to large linear chirp in the input pulse, spectral profile corresponds to the temporal distribution.

We demonstrated in the experiment conversion of a 40 ps bell-shaped pulse into a rectangular pulse, demanded, for example, in photoinjector technology. Our scheme showed itself as a cheap and easy alternative to SLM shaping, therefore we believe it can be interesting for some applications. (paper)

[en] It is demonstrated experimentally that at high average radiation power, the optical isolation in the recently proposed design of a Faraday isolator is substantially higher than in the conventional scheme. The Faraday isolator with the isolation of 45 dB at the radiation power of 100 W is implemented. The data obtained show that a 30-dB isolator for the average laser radiation power of 1 kW can be realised. (laser applications and other topics in quantum electronics)

[en] We report possible employment of short spatial filters based on spherical lenses in a pulsed laser source (neodymium glass, 300 J, 1 ns). The influence of the spherical aberration on the quality of output radiation and coefficient of conversion to the second harmonics is studied. The ultra-short aberration spatial filter of length 1.9 m with an aperture of 122 mm is experimentally tested. A considerable shortening of multi-cascade pump lasers for modern petawatt laser systems is demonstrated by the employment of short spatial filters without expensive aspherical optics. (elements of laser systems)

[en] Amplifiers based on neodymium phosphate glass rods 60 - 100 mm in diameter are experimentally studied. The amplifiers are pumped by INP-16/250 tubular flash lamps placed in a universal pump cavity with a two-section mirror reflector. A compact high-voltage capacitive energy storage with a preionisation circuit was developed to supply the lamps. (lasers)