Parametric amplifiers with multiple beams pumping for high-power laser systems of the femtosecond range

The possibilities of realization of the output amplifier cascade of a powerful laser system based on parametric amplification of femtosecond pulses with multiple beams pumping are investigated. A method for choosing the optimal arrangement of the pump beams of a parametric amplifier which makes it possible to achieve a broad spectral gain band with minimal losses from parametric diffraction is proposed. A number of optimal arrangements of the pump beams in LBO and DKDP crystals are chosen. Simulation results of the parametric amplification taking parametric diffraction into account are presented for these crystals. The dependence of the amplification efficiency and the amplified pulse duration on the number of pump beams is analyzed. Complete elimination of modulation of the spatial profile of the amplified radiation is demonstrated with the use of spatial filters in case of LBO crystal. The influence of small-scale self-focusing of the interference pattern of the total pump beam on the peak intensity of beams is investigated for LBO and DKDP crystals. It is shown that DKDP crystals are of little avail for multiple pump parametric amplification of fs pulses in 700- 900 nm spectral range.