High-order harmonic generation from laser plasma produced by pulses of different duration

Abstract

The high-order harmonic generation was analyzed by interaction of the femtosecond pulses with the laser plasma produced on the surfaces of various targets. The plasma formation was accomplished by the interaction of the prepulse radiation of different pulse duration ($160\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$, $1.5\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$, $210\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$, and $20\phantom{\rule{0.3em}{0ex}}\mathrm{ns}$) with the low-$Z$ (lithium, boron, carbon), medium-$Z$ (manganese, zinc, nickel), and high-$Z$ (silver, barium) targets. We showed that plasma formation conditions play a crucial role in harmonic generation and the optimization of this process mostly depends on the energy of prepulse rather than its intensity at the target surface. These studies also demonstrated that the delay between the prepulse and femtosecond pulse is another important parameter, which distinguishes harmonic generation in the cases of the low- and high-$Z$ targets.