Extracting electron dynamics in solids via observation of low-order harmonics of tailored strong fields.

阿秒科学的最新进展预示着固态物理学的范式变化。基于长脉冲和频域分析的旧框架目前正在被依赖于基于时间的图像和强超短脉冲的新框架所取代。在这个项目中，我们的目标是研究光学周期内部，利用时间和偏振定制的双色场以及基于光子晶体和纳米结构的定制样品几何形状来重建固体中的阿秒带间和带内动力学，以促进相位匹配和对称破缺。我们使用腔内增强近红外驱动场，从第一个QUTIF周期可用。在这些定制场中，可以有效地产生最低的辐射谐波。在之前的QUTIF期间也开发了一种方案，即所谓的全光阿托钟，仔细分析了谐波，允许重建电子动力学的细节，如阿托秒时间尺度上的电离延迟。理论预测，全光阿托钟能够解开低阶谐波产生背后的不同机制，即磁化率贡献（束缚-束缚），布鲁内尔辐射（无束缚），最后是再碰撞谐波（束缚-自由束缚）。本课题的目的是在实验和理论的密切相互作用下，在亚周期尺度上对半导体和电介质中的非线性电子动力学进行研究。这不仅可以更好地理解固体的非线性光学特性，而且还可以在太赫兹光谱范围内找到有效的谐波源。

Recent advances in attosecond science herald a paradigm change in solid-state physics. The old framework, based on long pulses and a frequency domain analysis is being currently replaced by the new one, relying on a time-based picture and strong ultrashort pulses. In this project we aim to look inside the optical cycle to reconstruct the attosecond inter- and intraband dynamics in solids using temporally and polarizationally tailored two-color fields as well as tailored sample geometries based on photonic crystals and nanostructures to facilitate phase-matching and symmetry breaking. We use the intracavity enhanced near-infrared driving fields available from the first QUTIF period. In these tailored fields, lowest radiation harmonics are efficiently generated. The harmonics are carefully analyzed with a scheme developed in the previous QUTIF period as well, the so-called all-optical attoclock, allowing to reconstruct the details of electron dynamics such as ionization delay on attosecond time scales. Theory predicts that the all-optical attoclock is capable of disentangling the different mechanisms behind the generation of low-order harmonics, namely the susceptibility contribution (bound-bound), the Brunel radiation (bound-free), and finally the re-collision harmonics (bound-free-bound). Aim of this project is the first experimental demonstration of the all-optical attoclock and the investigation of the nonlinear electron dynamics in semiconductors and dielectrics on the sub-cycle scale in close interplay between experiment and theory. This leads not only to a better understanding of the nonlinear optical properties of solids, but also to efficient harmonic sources e.g. in the THz spectral range.