Probing the effect of laser-carrier-envelop phase in frequency-comb high-order harmonic generation of He atoms.*

We present an ab initio nonperturbative study of the role of carrier envelop phase (CEP) of the laser pulse trains in frequency-comb high-order harmonic generation (HHG). The frequency-comb HHG is obtained by solving three-dimensional time-dependent Schrödinger equation of the He atom driven by the intense laser pulse trains. We find that the structures of frequency-comb HHG in plateau regions are very sensitive to CEP of the laser pulse trains, while the dependence of the low-energy and near-cutoff harmonics on CEP is not observed. In addition, the dynamics of frequency-comb HHG at the plateau regions are clarified. Our results enable us to obtain a clear understanding of the role of CEP of the laser pulse trains in frequency-comb HHG and provide an insight into the field of ultrafast science and technology.