title: Quasi-phase-matching high-harmonic radiation using chirped THz pulses.
abstract: High-order harmonic generation in the presence of a chirped THz pulse is investigated numerically with a complete 3D nonadiabatic model. The assisting THz pulse illuminates the high-order harmonic generation gas cell laterally inducing quasi-phase-matching. We demonstrate that it is possible to compensate the phase mismatch during propagation and extend the macroscopic cutoff of a propagated strong IR pulse to the single-dipole cutoff. We obtain 2 orders of magnitude increase in the harmonic efficiency of cutoff harmonics (≈170  eV) using a THz pulse of constant wavelength, and a further factor of 3 enhancement when a chirped THz pulse is used.
authors.affiliation: Department of Optics and Quantum Electronics, University of Szeged, HU-6720 Szeged, Hungary. kkovacs@itim-cj.ro
authors.forename: Katalin
authors.initials: K
authors.lastname: Kovács
authors.forename: Emeric
authors.initials: E
authors.lastname: Balogh
authors.forename: János
authors.initials: J
authors.lastname: Hebling
authors.forename: Valer
authors.initials: V
authors.lastname: Toşa
authors.forename: Katalin
authors.initials: K
authors.lastname: Varjú