Optical attosecond pulses and tracking the nonlinear response of bound electrons
Optical attosecond pulses and tracking the nonlinear response of bound electrons
复制标题
DOI：
10.1038/nature16528
复制
发表时间：
2016-02-04
期刊：
影响因子：
64.8
通讯作者：
Goulielmakis, E.
中科院分区：
文献类型：
--
作者：
Hassan, M. Th.;Luu, T. T.;Goulielmakis, E.
束缚电子对光的电磁力作出反应所需的时间，为物质的动态控制和电磁信号处理设定了基本的速度限制。物质非线性折射率（1）的时间积分测量表明，束缚电子对光场的非线性响应不是瞬时的;然而，非线性磁化率张量（2）的完整光谱表征-这对于使用光谱测量推断介质对任意驱动力的时间响应至关重要-尚未实现。随着阿秒计时法的建立（3-5），正能量电子对电磁场的脉冲响应已经通过极紫外阿秒脉冲（8）或强近红外场（9-11）电离原子（6）和固体（7）进行了探索。然而，没有阿秒的研究进行到目前为止，提供了直接访问的束缚电子的非线性响应。在这里，我们表明，在可见光和附近的光谱范围内合成的强烈的光学阿秒脉冲允许亚飞秒控制和计量的束缚电子动力学。氪原子的真空紫外光谱，暴露于强烈的波形控制的光学阿秒脉冲，揭示了一个有限的非线性响应时间的束缚电子高达115阿秒，这是敏感的和可控的超倍频程光场。我们的研究可以实现固体的原子，分子或晶格势中束缚电子的新光谱（12），以及在亚飞秒时间尺度上和以千兆赫速率运行的基于光的电子学（13-15）。
The time it takes a bound electron to respond to the electromagnetic force of light sets a fundamental speed limit on the dynamic control of matter and electromagnetic signal processing. Time-integrated measurements of the nonlinear refractive index(1) of matter indicate that the nonlinear response of bound electrons to optical fields is not instantaneous; however, a complete spectral characterization of the nonlinear susceptibility tensors(2)-which is essential to deduce the temporal response of a medium to arbitrary driving forces using spectral measurements-has not yet been achieved. With the establishment of attosecond chronoscopy(3-5), the impulsive response of positive-energy electrons to electromagnetic fields has been explored through ionization of atoms(6) and solids(7) by an extreme-ultraviolet attosecond pulse(8) or by strong near-infrared fields(9-11). However, none of the attosecond studies carried out so far have provided direct access to the nonlinear response of bound electrons. Here we demonstrate that intense optical attosecond pulses synthesized in the visible and nearby spectral ranges allow sub-femtosecond control and metrology of bound-electron dynamics. Vacuum ultraviolet spectra emanating from krypton atoms, exposed to intense waveform-controlled optical attosecond pulses, reveal a finite nonlinear response time of bound electrons of up to 115 attoseconds, which is sensitive to and controllable by the super-octave optical field. Our study could enable new spectroscopies of bound electrons in atomic, molecular or lattice potentials of solids(12), as well as light-based electronics operating on sub-femtosecond timescales and at petahertz rates(13-15).