中红外双色场量子轨道调控下宽谱带阿秒脉冲的产生

采用由2000 nm中红外驱动场和1000 nm弱倍频调制场组成的双色场作为驱动源，提出了产生水窗波段宽带高次谐波谱的新方法。弱倍频场对原子中电子的电离阶段进行调制，不仅扩大了连续谱的带宽，而且大大提高了连续谱的产生效率。通过求解一维氦原子模型下含时薛定谔方程，发现该双色场驱动下能够得到谱宽为190 eV的连续谱，并且较2000 nm中红外单色驱动下，连续谱谐波的效率提高了两个数量级。此外，计算中还发现调整双色场的相对载波包络相位，能够增强一个轨道电子的贡献同时抑制另一个电子轨道的贡献，利用这种方法能够得到脉宽为70 as的单阿秒脉冲。

Broad bandwidth attosecond pulse generation using mid-infrared two color field to control quantum trajectory

A method to generate a broadband water window continuum high-order harmonic generation spectra is proposed using a few-cycle two-color driving pulse synthesized by 2000 nm mid-infrared laser driving field and its much weaker 1000 nm second harmonic modulation field.In the scheme,the ionization step can be modulated by the weaker second harmonic,which not only broadens the bandwidth but also enhances the yields of the continuum harmonics.By solving time-dependent Schrodinger equation based on one-dimensional helium atom model,it is found that a broadband continuum harmonic spectrum with bandwidth of 190 eV is observed and the yield of the continuum harmonics is increased by two orders compared with one-color 2000 nm driving field alone.Furthermore,adjusting the carrier envelop phase between the two-color field can enhance the contribution of one ionization trajectories and simultaneously suppress the other one,from which an isolated 70 as pulse can be obtained.