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

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．

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

We investgate the high-order harmonic generation(HHG) emission of helium atom exposed to the midinfrared fields( =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 spectra on the platuea near the cut-off are obtained. As a result, an isolated 44.5as pulse is generated by superposing 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 gating are suppressed when the polarization gating is used, thus a single isolated ultrashort pulse can be generated.