Control of high-order single harmonic pulse by using half-cycle laser pulse

In order to obtain the high-order single harmonic pulse with the adjustable photon energy, through solving the time-dependent Schrödinger equation, the characteristics for producing the high-order single harmonic pulse has been investigated when He atom is driven by a special chirped waveform combined with a half-cycle laser pulse. The results show that, under the control of the positive half-cycle laser pulse, the high-order single harmonic pulse changes from the 125th order to the 97th order, which means the high-order single harmonic pulse moving to the low energy region with the increase of the half-cycle laser delay. Under the control of the negative half-cycle laser pulse, the high-order single harmonic pulse changes from the 125th order to the 157th order, which means the high-order single harmonic pulse moving towards to the high energy region with the increase of the half-cycle laser delay. Moreover, with the increase of the intensity of the half-cycle laser pulse, the movement of the high-order single harmonic pulse is more obvious. This result is helpful for obtaining the high-order single harmonic pulse light source.