利用43飞秒的强激光脉冲实现单个阿秒脉冲输出的新机理

Proposal for single attosecond pulse production with a 43-fs super intense laser pulse

研究了多个光周期的长脉冲(43fs)激光与氖原子相互作用产生的高次谐波的辐射特性.通过计算机数值模拟,发现当激光场的强度超过饱和光强时,原子将会在几个光周期内被迅速电离,使得原子的高次谐波谱在截止区呈现出平滑的多平台结构.同时,在高频波段离子产生的高次谐波的影响将变得十分显著.通过选取合适的子平台进行频率叠加,在消除了离子的高次谐波的影响后,可以获得单个的阿秒软X射线脉冲.

High harmonics generation （HHG） from Ne atom driven by a multi-cycle 43 fs laser pulse is investigated. The numerical simulation demonstrates that when the intensity of the driving laser is over-saturated, the atom will be ionized rapidly during a few optical cycles, this will lead to a continuous multi-plateau structure in the cutoff region of the high harmonics spectrum from the neutral atom. It is also shown that the signal of high-order harmonics from the ion becomes remarkable when the driving laser is super intense. The superposition of an appropriate sub-platean can give single attosecond soft X-ray pulse, and the effect of HHG from ion has been eliminated through the band selection.