Role of carrier-envelope phase on below-threshold high-order harmonic generation of Ar atom.

 We theoretically study the dependence of carrier-envelope phase (CEP) on high-order harmonic generation (HHG) of Ar atom in the few cycle laser pulses.  The HHG spectra can be calculated accurately and efficiently by solving three-dimensional time-dependent Schrödinger equation by means of the time-dependent generalized pseudospectral method.  We find that the yields of near- and below-threshold HHG is sensitive to the CEP of the laser pulse. Combining with a wavelet transform of the quantum time-frequency spectrum and an extended semiclassical analysis, the role of CEP on the near- and below-threshold harmonic generation processes is clarified.