"Measuring the orbital angular momentum spectrum of an electron beam"
Vincenzo Grillo, Amir H Tavabi, Federico Venturi, Hugo Larocque, Roberto Balboni, Gian Carlo Gazzadi, Stefano Frabboni, Peng-Han Lu, Erfan Mafakheri, Frédéric Bouchard, Rafal E Dunin-Borkowski, Robert W Boyd, Martin PJ Lavery, Miles J Padgett and Ebrahim Karimi
Nature Communications, Volume: 8 Pages: 15536
Published online: 24 May 2017, doi:10.1038/ncomms15536
Electron waves carrying an Orbital Angular Momentum (OAM) can be generated through a variety of methods by directly interacting with the electrons’ wavefronts. These processes rely on devices such as spiral phase plates amplitude and phase holograms, cylindrical lens mode converters or even electron microscope corrector lenses. In addition to diffraction and interference, this kind of electron waves show additional mechanical and magnetic properties that, upon elastic interaction with matter, allow for probing magnetic chirality as well as magnetic dichroism and more generally provide novel insights into the quantum nature of electromagnetic–matter interaction. Here V. Grillo and co-workers propose, design, and demonstrate the performance of a device for measuring the azimuthal wavefunction of an electron beam, i.e. its OAM, based on nanoscale holograms. The device is also employed to analyse the OAM spectrum of electrons affected by a micron-scale cobalt magnetic dipole.