Speaker
Matthias Wollenhaupt
(Carl von Ossietzky Universität, Oldenburg)
Description
Recently, the emergence of vortex structures in the momentum distribution of free electron wave packets from photoionization of atoms with sequences of two time-delayed counterrotating circularly polarized (CRCP) ultrashort laser pulses was predicted [1] and demonstrated experimentally [2]. Electron vortices arise from the superposition of two time-delayed free electron wave packets with different magnetic quantum numbers. In our experiment three-dimensional electron vortices are generated by multiphoton ionization of potassium atoms using CRCP femtosecond laser pulses from a polarization-shaped supercontinuum source [3] and reconstructed tomographically from velocity map imaging (VMI) measurements [4]. Absorption of another photon in the continuum changes the c6 azimuthal symmetry of the threshold vortex into c8 for above threshold ionization (ATI) [5]. Electron vortices from non-perturbative excitation show c4 azimuthal symmetry and a pi-phase jump in the polar direction. Currently, we study electron vortices generated by bichromatic polarization-shaped CEP-stable supercontinua [3].
[1] J. M. Ngoko Djiokap et al., Phys. Rev. Lett. 115, 113004 (2015).
[2] D. Pengel et al., Phys. Rev. Lett. 118, 053003 (2017).
[3] S. Kerbstadt et al., Opt. Express 25, 12518 (2017).
[4] S. Kerbstadt et al., New J. Phys. 19, 103017 (2017).
[5] D. Pengel et al., Phys. Rev. A 96, 043426 (2017).
Author
Matthias Wollenhaupt
(Carl von Ossietzky Universität, Oldenburg)
