Quasi-phase-matching-induced enhancement of high-order harmonics during two-colour pump of multi-jet plasmas

The first demonstration of quasi-phase-matching during high-order harmonic generation (HHG) of laser radiation in multi-jet plasmas produced on the silver and chromium targets under the conditions of two-colour pump (804 and 402 nm) is presented. We analyse the enhancement of the groups of odd and even harmonics along the plateau range and compare the harmonic yields using a different number of plasma jets. The comparison of extended line plasma and multi-jet plasma shows the advanced properties of the latter formation for the efficient HHG using the two-colour pump. The 25× and 13× enhancement factors of quasi-phase-matched harmonics were obtained in the cases of the two-colour and single-colour pumps of multi-jet plasmas. (paper)