Probing the spatio-temporal properties of strong field harmonic emission in the liquid phase

在过去的十年中，对原子系统中非微扰现象的研究已成为一个活跃的研究领域。特别是相干和强场物质相互作用，如通过高次谐波产生（HHG）的XUV辐射及其阿秒时间结构的产生是非常有趣的。直到最近，人们的注意力才转向在分子、气相团簇和表面等更复杂的系统中研究HHG。在强场-物质相互作用的背景下，很大程度上尚未开发的仍然是液相。本文的目的是通过实验详细研究液态水滴中HHG的非摄动过程。特别是研究潜在的产生机制，标度规律和使用电磁场相干控制的过程效率是非常有趣的。第二步，在液态水基质中进行纳米颗粒的控制包埋，以研究和定制谐波发射特性。将纳米颗粒装入液滴中，可以对量子约束效应进行研究。因此，最小化粒子尺寸可以导致最大光子能量的增加，这是由于粒子内带隙的增加。高谐波光谱将用于研究纳米粒子的时空特性。最后，我们的目标是开发一种易于获得的实验技术，然后可以在许多应用中使用。

The study of non-perturbative phenomena in atomic systems has become a vivid field of research during the last decade. In particular coherent and strong field-matter interactions such as the generation of XUV radiation through high-order harmonic generation (HHG) and its attosecond time structure are of sound interest. Only recently, the attention has turned towards the investigation of HHG in more complex systems like molecules, clusters in the gas phase and surfaces. Largely unexplored is still the liquid phase in the strong field-matter interaction context.The goal of this proposal is to study in detail the non-perturbative process of HHG in liquid water droplets experimentally. In particular the investigation of the underlying generation mechanism, the scaling laws and the efficiency of the process using coherent control of electromagnetic fields is of great interest. In a second step the controlled embedding of nanoparticles in the liquid water matrix will be conducted in order to investigate and tailor the harmonic emission characteristics. Loading the droplets with nanoparticles allows for an investigation of the quantum confinement effect. Minimizing the particle size can therefore lead to an increase of the maximum photonic energy due to an increasing band-gap within the particle. High-harmonic spectroscopy will then serve to study the spatio-temporal properties of the nanoparticles. Finally, we aim to develop a readily available experimental technique that can then be used in numerous applications.