Orbital angular momentum superposition states in transmission electron microscopy and bichromatic multiphoton ionization

Abstract

The coherent control of electron beams and ultrafast electron wave packet dynamics have attracted significant attention in electron microscopy as well as in atomic physics. In order to unify the conceptual pictures developed in both fields, we demonstrate the generation and manipulation of tailored electron orbital angular momentum (OAM) superposition states either by employing customized holographic diffraction masks in a transmission electron microscope or by atomic multiphoton ionization utilizing pulse-shaper generated carrier-envelope phase stable bichromatic ultrashort laser pulses. Both techniques follow similar physical mechanisms based on Fourier synthesis of quantum mechanical superposition states allowing the preparation of a broad set of electron states with uncommon symmetries. We describe both approaches in a unified picture based on an advanced spatial and spectral double slit and point out important analogies. In addition, we analyze the topological charge and discuss the control mechanisms of the free-electron OAM superposition states. Their generation and manipulation by phase tailoring in transmission electron microscopy and atomic multiphoton ionization is illustrated on a 7-fold rotationally symmetric electron density distribution.

Carrier-envelope-phase and helicity control of electron vortices in photodetachment

“…( 1 Note that an extra phase term here does not contribute to the contour integral in Eq. (11). This explains why the vortex-like points, while located at the same momenta, will carry opposite topological charges in both cases.…”

“…During the last decade there has been an increasing interest towards the electron momentum spirals (often referred as 'vortices') in laser-induced photoionization [1][2][3][4][5][6][7][8][9][10][11][12] or photodetachment [13]. They manifest themselves, in the probability distribution of photoelectrons, as zones of large probability which follow concentric Fermat spirals with well-defined number of arms [1].…”

Multichromatic Polarization-Controlled Pulse Sequences for Coherent Control of Multiphoton Ionization

“…where e ε and e ϕ denote the respective unit vectors in energy and azimuthal direction. A detailed discussion of the probability density current of vortex states can be found in [105,106,156]. Interestingly, PMDs exhibiting simultaneously helical interference structures and a non-vanishing azimuthal probability density current (Eq.…”

Shaping of Electron Beams Using Sculpted Thin Films

“…Numerical investigations of electron vortices propagating through amorphous materials have been performed. 42 Recently, methods to generate OAM using amplitude masks and laser-assisted multiphoton ionization 43 have been compared. The shaping of an electron probe into an electron vortex beam in a scanning electron microscope (SEM), rather than a TEM, has also been shown.…”