极化门控制下中红外激光场驱动He原子产生的单个阿秒脉冲

An isolated attosecond pulse emission of He atom driven by the midinfrared laser field with polarization gating

由中红外激光场(波长为2128nm)驱动He原子,在极化门的控制下,通过强场近似方法(SFA)研究了He原子发射高次谐波的特点.研究表明,在这种组合场驱动下He原子可产生截止位置很高的高次谐波,并且在接近截止位置的平台区展现了超连续的特点,对该超连续部分的高次谐波进行叠加,可得到宽度为44.5as的单个超短脉冲.为了了解该超短阿秒脉冲的产生机理,我们对高次谐波谱的发射过程进行了时频分析,分析表明由于极化门的存在,有效地抑制了极化门以外的阿秒脉冲的发射,从而获得单个阿秒脉冲.

We investgate the high-order harmonic generation（ HHG） emission of helium atom exposed to the midinfrared fields（λ=2128nm） with polarization gating by the strong field approximation（SFA） method.It is shown that the cut-off of HHG from helium atom driven by the fields is extended, and the supercontinuum spec-tra on the platuea near the cut-off are obtained.As a result, an isolated 44.5as pulse is generated by superpo-sing the some range of the supercontinuum spectra.In order to explain the emission process of HHG, we also perform the time-frequency analysis.Our results indicate that the emission of attosecond pulses outside the ga-ting are suppressed when the polarization gating is used, thus a single isolated ultrashort pulse can be generated.