阿秒瞬态偏振测量
Attosecond Transient Polarimetry
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中文总结 AI 辅助
研究提出椭圆二向色性阿秒瞬态吸收光谱（eDATAS）技术，将圆、线二向色性阿秒瞬态吸收光谱作为其极限情况，通过氦气实验验证理论，还可原位测量XUV场偏振态。
中文摘要 AI 辅助
我们引入椭圆二向色性阿秒瞬态吸收光谱（eDATAS），这是一种超快阿秒光谱技术，其中原子气体由椭圆偏振的阿秒脉冲和近红外脉冲探测，两个脉冲的偏振椭圆之间夹角任意且时间延迟可变。利用微扰理论，我们证明瞬态吸收信号可分解为形状因子，其对脉冲椭圆率和偏振椭圆取向的依赖完全由偶极选择定则决定：椭圆率设定干涉多光子路径的振幅，而椭圆的相对取向控制相位。我们将圆二向色性和线二向色性阿秒瞬态吸收光谱重新解释为eDATAS的极限情况，并通过氦气中的eDATAS测量验证该理论，发现吻合度极佳。最后，我们证明eDATAS还可作为XUV场偏振态的原位测量工具，无需专用的XUV偏振仪。
英文摘要
We introduce elliptical-dichroic attosecond transient absorption spectroscopy (eDATAS), an ultrafast attosecond spectroscopy technique in which an atomic gas is probed by elliptically polarized attosecond and near-infrared pulses with an arbitrary angle between the polarization ellipses and a varying time-delay. Using perturbation theory, we show that the transient absorption signal factorizes into form factors whose dependence on pulse ellipticities and polarization-ellipse orientations are governed entirely by dipole selection rules: ellipticity sets the amplitudes of the interfering multiphoton pathways, while the relative orientations of the ellipses control the phase. We reinterpret circular- and linear-dichroic attosecond transient absorption spectroscopy as limiting cases of eDATAS, and validate the theory through an eDATAS measurement in helium, finding excellent agreement. Finally, we demonstrate that eDATAS can also serve as an in situ measurement of the polarization state of the XUV field, avoiding the need for a dedicated XUV polarimeter.
