Active and passive spatial modulation of free-electron wavepackets via ultrafast plasmonic excitations

  Shai Tsesses  ,  Raphael Dahan  ,  Kangpeng Wang  ,  Ori Reinhardt  ,  Guy Bartal  ,  Ido Kaminer  
Andrew and Erna Viterbi department of Electrical Engineering, Technion - Israel Institute of Technology

Spatial modulation of electron beams is of paramount importance for both academic and industrial applications, such as nanolithography, microscopy and material studies. Though passive spatial modulation of electrons is quite common, using various methods, actively shaping electrons is an open challenge. Here, we use ultrafast plasmonic excitations to perform passive and active spatial modulation of free-electron wavepackets, building on recent experiments. Passively, we generate vortex, vortex array and quasi-periodic electron wavefunctions. Actively, we vary the electron shape by externally controlling the plasmonic nearfield distribution, continuously tuning the electron angular momentum quantity. We further present the first demonstration of 2D spatial Rabi-like oscillations, occurring due to the interaction nonlinearity, and utilize them to generate electron features far below the plasmonic diffraction limit. Our work paves the way to on-demand electron wavefront shaping, with applications in aberration correction, super-resolution, nano-fabrication and characterization of magnetic materials.