[en] A new scheme of a cascaded converter of the first harmonic of broadband cw laser radiation into the second harmonic (SH) with compensation for the group walk-off in cascades is proposed and investigated. The conditions under which high conversion coefficients of broadband (∼33 cm^-1) single-mode fibre laser radiation with low peak power (∼300 W) into the SH are determined for frequency doublers based on the most promising LBO crystal. Conversion of cw radiation with an average power of 300 W and efficiency η = 4.5 % into the SH is obtained in a single LBO crystal. Effect of coherent addition of SH radiation excited in different cascades is demonstrated for two- and three-stage schemes. The expected conversion efficiencies, calculated disregarding loss but taking into account real aberrations of elements, are 18 % and 38 %, respectively. The effect of pumping depletion begins to manifest itself in the third cascade of a three-stage converter; it may reduce the latter value to ∼30 %. (nonlinear optical phenomena)

[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] The projected KLOD facility is intended for finding and investigating the ultrarare decay K_L^0→ π⁰νν-bar; its branching ratio predicted by the Standard Model is Br = (3.0 ± 0.6) x 10^-11. Designing and testing the prototype of the decay-volume veto system and beam veto calorimeter, which are the most important detectors of the facility, are considered. It is shown that the proposed beam veto calorimeter is able to detect γ rays with a high efficiency at the neutron flux of 300 MHz.