We theoretically investigate the high-order harmonic generation (HHG) driven by dual-pulse lasers. The first pulse of 800nm can create plasma in the high-density gas target. Then, the second pulse of 1800nm is spatiotemporally reshaped by the plasma and generates soft x-ray high-order harmonics in the overdriven regime. The simulation results show that adding the first pulse can promote the phase matching of HHG in the cutoff region. As a result, a cutoff-extended HHG is achieved, which is one order of magnitude more intense than that in one pulse scheme reported previously. In dual-pulse driving lasers, the harmonic yield and the cutoff photon energy can be optimized effectively by increasing the gas pressure inside the water window region.

我们从理论上研究了双脉冲激光器驱动的高次谐波产生 (HHG)。800nm 的第一个脉冲可以在高密度气体靶中产生等离子体。然后，1800nm 的第二个脉冲被等离子体在时空上重塑，并在过驱动状态下产生软 X 射线高次谐波。仿真结果表明，加入第一个脉冲可以促进HHG在截止区域的相位匹配。结果，实现了截止扩展的 HHG，其强度比先前报道的一种脉冲方案中的强度高一个数量级。在双脉冲驱动激光器中，通过增加水窗区域内的气体压力可以有效地优化谐波产额和截止光子能量。