Department of Physics, The Ohio State University, Columbus, OH, 43210, USA.
Nat Commun. 2023 May 5;14(1):2603. doi: 10.1038/s41467-023-38187-0.
Studies of laser-driven strong field processes subjected to a (quasi-)static field have been mainly confined to theory. Here we provide an experimental realization by introducing a bichromatic approach for high harmonic generation (HHG) in a dielectric that combines an intense 70 femtosecond duration mid-infrared driving field with a weak 2 picosecond period terahertz (THz) dressing field. We address the physics underlying the THz field induced static symmetry breaking and its consequences on the efficient production/suppression of even-/odd-order harmonics, and demonstrate the ability to probe the HHG dynamics via the modulation of the harmonic distribution. Moreover, we report a delay-dependent even-order harmonic frequency shift that is proportional to the time derivative of the THz field. This suggests a limitation of the static symmetry breaking interpretation and implies that the resultant attosecond bursts are aperiodic, thus providing a frequency domain probe of attosecond transients while opening opportunities in precise attosecond pulse shaping.
受（准）静态场驱动的强场过程的研究主要局限于理论。在这里，我们通过引入双色方法在介电质中实现了高次谐波产生（HHG），该方法结合了强 70 飞秒持续时间的中红外驱动场和弱 2 皮秒周期太赫兹（THz）调制场。我们研究了 THz 场诱导的静态对称破缺的物理基础及其对偶数/奇数谐波的有效产生/抑制的影响，并通过调制谐波分布来证明探测 HHG 动力学的能力。此外，我们报告了与 THz 场的时间导数成正比的延迟相关的偶数阶谐波频率移动。这表明静态对称破缺解释存在局限性，并暗示所得的阿秒脉冲是无周期的，从而提供了阿秒瞬变的频域探针，同时为精确的阿秒脉冲整形开辟了机会。
