Freiburg 2024 – scientific programme

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A: Fachverband Atomphysik

A 10: Interaction with Strong or Short Laser Pulses I (joint session A/MO)

A 10.5: Talk

Tuesday, March 12, 2024, 12:15–12:30, HS 1010

Shaped free electron vortices — •Darius Köhnke, Tim Bayer, and Matthias Wollenhaupt — Carl von Ossietzky university Oldenburg, Institute of Physics, Germany

Since their first theoretical proposal [1] and their experimental demonstration [2], free electron vortices have attracted significant attention. Very recently, a novel category of electron spirals, termed "reversible electron spirals" [3], was introduced. Departing from the conventional approach of employing a constant delay between two subpulses, two chirped subpulses were used. Building on this concept, we introduce tailored free electron vortices in multiphoton ionization (MPI) using two subpulses with circular polarization of opposite handedness, modulated by non-trivial spectral phase functions. Through the utilization of different MPI pathways, the quantum system multiplexes the fields of the subpulses, generating multiple complex spectral phases. These spectral phases are encoded in continuum states characterized by different magnetic quantum numbers. The interference of these continuum states gives rise to multiple interferograms of different symmetry that are multiplexed into a single 3D photoelectron momentum distribution. To demultiplex these interferograms and extract the encoded spectral phases, we perform photoelectron tomography and employ Fourier analysis on the measured wave packet. This approach enables the retrieval of spectral information, both from the input laser fields and signatures of the ionization process, embedded within the interferograms. [1] Phys. Rev. Lett. 115, 113004 (2015), [2] Phys. Rev. Lett. 118, 053003 (2017), [3] Phys. Rev. A 106, 043110 (2022)

Keywords: free electron vortices; photoelectron tomography; photoelectron holography; femtosecond pulse shaping; multiphoton ionization