Pulse-shape effects on high-order harmonic generation from a periodic potential field

We study here the high-order harmonic generation from a one-dimensional periodic potential field driven by few-cycle laser pulses, and special attention is paid to the effects of the pulse shapes on the HHG spectra distribution. The time-dependent Schrödinger equation based on the energy band theory and the Bloch theorem is employed to describe the evolution of the electronic wave packet in the periodic potential driven by the intense pulsed laser field. The energy band structures and the Bloch functions are computed using the plane wave expansion method and the time-dependent Schrödinger equation is solved using the split operator numerical scheme. It is found that the harmonic spectra generated with pulses of different waveforms all have two-plateau structure. However, the detailed structures as well as the intensity of the higher order harmonics are quite different, especially for the second spectral plateau.