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Optimization of a multibeam-pumped optical parametric amplifier.

The results of numerical simulation of the output amplifier cascade of a powerful laser system based on the parametric amplification of femtosecond pulses in an LiB3O5 crystal with multiple beams pumping are presented. The improved technique for choosing pump beam angles with minimal parasitic amplification is presented. Differences of carrier-resolving versus envelope simulations are discussed. Results for pulse energy, duration, and fraction of parasitic energy are presented. It has been established that with an increase in the number of pump beams up to 11 beams, the duration of the amplified pulse increases insignificantly from 20 to 21 fs in the case of incoherent pumping beams and increases to 26 fs in the case of coherent ones. At the same time, the amplification efficiency decreases from 23% to 21% in the first case and drops to 10% in the second case. Influence of small-scale, self-focusing of the pump field interference pattern on peak intensity is discussed.