Two-color high-harmonic generation in plasmas: efficiency dependence on the generating particle properties.

The high-order harmonic generation (HHG) in silver, gold, and zinc plasma plumes irradiated by orthogonally polarized two-color field is studied theoretically and experimentally. We find an increase of the HHG efficiency in comparison with the single-color case, which essentially depends on the plasma species and harmonic order. An increase of more than an order of magnitude is observed for silver plasma, whereas for gold and zinc it is lower; these results are reproduced in our calculations that include both propagation and microscopic response studies.

Frequency tunable single attosecond pulse production from aligned diatomic molecules ionized by intense laser field.

We present the detailed theoretical study of single attosecond pulse production from excited molecules driven by intense laser pulse. We demonstrate the possibility for continuously tunable soft x-ray production via high-order harmonic generation from a stretched aligned molecule undergoing Coulomb-barrier suppression ionization. This frequency tuning results from the quantum interference of free-electron wave packets emanating from different nuclei.