Laurent G, Cao W, Ben-Itzhak I, Cocke C L
James R Macdonald Laboratory, Physics Department, Kansas State University, Manhattan, Kansas 66506, USA.
Opt Express. 2013 Jul 15;21(14):16914-27. doi: 10.1364/OE.21.016914.
In this work we propose a novel procedure for the characterization of attosecond pulses. The method relies on the conversion of the attosecond pulse into electron wave-packets through photoionization of atoms in the presence of a weak IR field. It allows for the unique determination of the spectral phase making up the pulses by accurately taking into account the atomic physics of the photoionization process. The phases are evaluated by optimizing the fit of a perturbation theory calculation to the experimental result. The method has been called iPROOF (improved Phase Retrieval by Omega Oscillation Filtering) as it bears a similarity to the PROOF technique [Chini et al. Opt. Express 18, 13006 (2010)]. The procedure has been demonstrated for the characterization of an attosecond pulse train composed of odd and even harmonics. We observe a large phase shift between consecutive odd and even harmonics. The resulting attosecond pulse train has a complex structure not resembling a single attosecond pulse once per IR period, which is the case for zero phase. Finally, the retrieval procedure can be applied to the characterization of single attosecond pulses as well.
在这项工作中，我们提出了一种用于阿秒脉冲表征的新方法。该方法依赖于在弱红外场存在的情况下，通过原子的光电离将阿秒脉冲转换为电子波包。通过精确考虑光电离过程的原子物理学，它能够唯一地确定构成脉冲的光谱相位。通过优化微扰理论计算与实验结果的拟合来评估相位。由于该方法与PROOF技术[Chini等人，《光学快报》18, 13006 (2010)]有相似之处，所以被称为iPROOF（通过ω振荡滤波改进的相位恢复）。该方法已被用于表征由奇次和偶次谐波组成的阿秒脉冲序列。我们观察到连续奇次和偶次谐波之间存在很大的相移。所得到的阿秒脉冲序列具有复杂的结构，不像零相位时每个红外周期出现一次单个阿秒脉冲的情况。最后，该恢复过程也可应用于单个阿秒脉冲的表征。
