Identifying multichannel transition paths between conduction bands in harmonic generation from solids

The ultrafast dynamics of the electron from solids are investigated by a periodic potential model. High-order-harmonic generation (HHG) is simulated by solving the time-dependent Schodinger equation. The quantum path of HHG is complex in solid system, multichannel paths contributing the second plateau region are identified in this paper. Our simulations show that the HHG contributed from the transitions between the conduction bands (CBs) cannot be ignored when the population in high CBs is considerable. A scheme is provided to enhance the HHG by adding a weak pulse to strengthen the transition between the CBs. The physical mechanism is discussed by the time-frequency and quasi-classical analysis.