Jia Cheng, Wang Jun, Li Qing-Yi, Guo Fu-Ming, Chen Ji-Gen, Zeng Si-Liang, Yang Yu-Jun
Opt Express. 2015 Dec 14;23(25):32222-9. doi: 10.1364/OE.23.032222.
We theoretically study high-order harmonic generation (HHG) and attosecond pulses from an atom irradiated synchronically by a terahertz (THz) pulse and an infrared laser pulse. For the HHG spectrum from the THz pulse alone and the combined pulse, an apparent peak-valley structure appears the platform region. Specially, for the periodic structure generated by an atom under the action of the combined pulse is originated from the interference between the electrons ionized at different instants in the laser field, which undergo many recollision and return to the core at the same time. Therefore, continuum harmonics with few chirps from the interference enhancement region can be achieved, which result in a chirp-free isolated attosecond pulse.
我们从理论上研究了太赫兹（THz）脉冲和红外激光脉冲同步辐照原子时的高次谐波产生（HHG）和阿秒脉冲。对于单独的太赫兹脉冲以及组合脉冲产生的高次谐波谱，在平台区域出现了明显的峰谷结构。特别地，组合脉冲作用下原子产生的周期性结构源于激光场中不同时刻电离的电子之间的干涉，这些电子经历多次再碰撞并同时返回原子核。因此，可以从干涉增强区域获得啁啾很少的连续谐波，从而产生无啁啾的孤立阿秒脉冲。
