Abstract. We present quantum and classical investigation on high order harmonic generation from twocolor scheme by employing different infrared (ir) laser parametric source as control pulse with locked carrier envelope phase. We found harmonic continuum bandwidth is in the function of the negative square of the ir-control pulse's wavelength from ir parametric source control field. Moreover, harmonic continuum bandwidth shows a linear dependence on the relative strength ratio k and achieves its extreme value when relative phase shift is around zero. A broad continuum with spectral width of 264 eV is observed from a combination field by 6 fs, 800 nm, 6 × 10 14 W/cm 2 few-cycle fundamental pulse and half-harmonic control pulse with k = 0.5. By further applying a second 10-um ir control pulse, a continuum beyond 353 eV is obtained which supports the generation of an isolated 12 attosecond (as) pulse.

By solving the time-dependent Schrödinger equation numerically, theoretically we study the high-order harmonics of a model He + ion exposed to the combined field of an intense chirped laser pulse and its high frequency pulse, and analyze the characteristics of the attosecond pulse produced by the high-order harmonics (HHG). Due to the presence of the chirped pulse and the high frequency pulse in the case of the combined fields, it is shown that the plateau of the high-order harmonics is extended largely and the conversion efficiency of high-order harmonics is enhanced effectively. By superimposing some orders harmonics in different region of the second plateau, all of the pulses obtained are single attosecond ones, minimum pulse achieves 21 as. To better understand the physical reasons of HHG enhancement and attosecond pulse emission, we perform classical analysis and the time-frequency analysis. combined field, high-order harmonics, attosecond pulse