Extension of the high-order-harmonic-generation cutoff frequency by two-color elicitation - art. no. 063816

We study high-order harmonic generation resulting from a two-color scheme i nvolving a circularly polarized high-frequency field and a weak linearly po larized low-frequency field. Although the low-frequency field is not intens e enough to ionize the atom, it can accelerate the electron more efficientl y. As a result, the application of this field can generate harmonics with m uch higher energy compared to the monochromatic case. For a hydrogenlike at om irradiated by a Nd:YAG (yttrium aluminum garnet) laser of intensity 1.9 x 10(14) W/cm(2) and a CO2 laser of intensity 7.6 x 10(12) W/cm(2), the cut off occurs at the 241st harmonic-order corresponding to a photon energy of 281 eV, which is three times higher than that of the monochromatic case.