Photoelectron tomography of electron vortices from tailored CEP-stable few-cycle and multicolour optical fields

利用载波包络相位（CEP）稳定偏振定制飞秒激光场操纵相干光诱导电子动力学是QUTIF第二个资助期的核心科学目标。在QUTIF的第一个资助期内，我们实现了一个超连续介质偏振脉冲成形器，用于产生定制的cep稳定的少周期脉冲和可变频率比的双色场[Opt. Express 25(2017) 12518]。利用反旋转圆极化脉冲序列与光电子断层扫描相结合，我们首次在实验中展示了原子多光子电离产生的自由电子漩涡[物理学]。Rev. Lett. 118(2017) 053003]在理论和实验上都引起了很大的关注。在QUTIF的第二个资助期，我们计划扩展我们的初步研究，通过使用偏振定制的cep稳定的少周期和多色飞秒激光场，探索模型系统的多光子电离的先进物理驱动相干控制方案。特别强调的是利用基于脉冲形状器的相位稳定超连续辐射的可变频率比双色场来操纵M光子与n光子干涉的控制场景的实现。我们最初的研究重点将放在自由电子涡流的先进相干控制上。例如，我们将通过具有相反宇称的离子态干涉来展示具有奇数臂的cep敏感双色自由电子涡，包括单臂涡，映射里德堡型束缚态动力学，并通过连续体中的光谱干涉来测量频率混合路径的电离时间。首先，我们将在微扰状态下的准单电子和多电子系统上验证这些方案，并继续在非微扰和隧道电离状态下探索这些方案。利用光电子层析成像测量的三维光电子动量分布来提取受控量子动力学的详细信息。我们将通过两项技术改进来完善我们的实验设置：(1)在我们的光电子能谱仪中安装原子/分子束来抵消gy相的空间cep平均；(2)设计和实现一个“TWIN-shaper”，即一种用于cep稳定超连续的新型偏振shaper。结合“TWIN-shaper”提供对电场形状的精确控制，并通过光电子断层扫描进行高度差分检测，将使我们能够展示原子和分子中相干电子动力学的前所未有的操作。

Manipulating coherent light-induced electron dynamics with Carrier Envelope Phase (CEP) stable polarization-tailored femtosecond laser fields is a scientific objective at the heart of the second funding period of QUTIF.In the first funding period of QUTIF, we have implemented a supercontinuum polarization pulse shaper for the generation of tailored CEP-stable few-cycle pulses and bichromatic fields with variable frequency ratios [Opt. Express 25 (2017) 12518]. Using counterrotating circularly polarized pulse sequences in combination with photoelectron tomography, we presented the first experimental demonstration of free electron vortices from multiphoton ionization of atoms [Phys. Rev. Lett. 118 (2017) 053003] which have attracted much attention, both theoretically and experimentally.In the second funding period of QUTIF, we plan to extend our preliminary research by exploring advanced physically motivated coherent control scenarios for multiphoton ionization of model systems using polarization-tailored CEP-stable few-cycle and multicolour femtosecond laser fields. Special emphasis lies on the implementation of control scenarios to manipulate M- vs. N-photon interferences using pulse shaper-based variable frequency-ratio bichromatic fields from phase-stable supercontinuum radiation. The initial focus of our investigations will be on advanced coherent control of free electron vortices. For example, we will demonstrate CEP-sensitive bichromatic free electron vortices with an odd number of arms, including a single-armed vortex, by interference of ionic states with opposite parity, map Rydberg-type bound state dynamics and measure the ionization time of frequency mixing pathways by spectral interference in the continuum. Initially, we will validate these scenarios on quasi-one- and multi-electron systems in the perturbative regime and continue to explore these schemes in the non-perturbative and tunnel ionization regime. Three-dimensional photoelectron momentum distributions, measured by photoelectron tomography, are utilized to extract detailed information on the controlled quantum dynamics. We will refine our experimental set-up by two technical improvements: (1) the installation of an atomic / molecular beam in our photoelectron spectrometer to counteract spatial CEP-averaging by the Gouy phase and (2) the design and implementation of a ‘TWIN-shaper’, i.e. a novel polarization shaper for CEP-stable supercontinua. Combining the ‘TWIN-shaper’ to provide precise control on shape the electric field with highly differential detection by photoelectron tomography will allow us to demonstrate unprecedented manipulation of coherent electron dynamics in atoms and molecules.