%0 Journal Article
%A Pozzi, Giulio
%A Grillo, Vincenzo
%A Lu, Peng-Han
%A Tavabi, Amir H.
%A Karimi, Ebrahim
%A Dunin-Borkowski, Rafal E.
%T Design of electrostatic phase elements for sorting the orbital angular momentum of electrons
%J Ultramicroscopy
%V 208
%@ 0304-3991
%C Amsterdam
%I Elsevier Science
%M FZJ-2020-02662
%P 112861 -
%D 2020
%X The orbital angular momentum (OAM) sorter is a new electron optical device for measuring an electron’s OAM. It is based on two phase elements, which are referred to as the “unwrapper” and “corrector” and are placed in Fourier-conjugate planes in an electron microscope. The most convenient implementation of this concept is based on the use of electrostatic phase elements, such as a charged needle as the unwrapper and a set of electrodes with alternating charges as the corrector. Here, we use simulations to assess the role of imperfections in such a device, in comparison to an ideal sorter. We show that the finite length of the needle and the boundary conditions introduce astigmatism, which leads to detrimental cross-talk in the OAM spectrum. We demonstrate that an improved setup comprising three charged needles can be used to compensate for this aberration, allowing measurements with a level of cross-talk in the OAM spectrum that is comparable to the ideal case.
%F PUB:(DE-HGF)16
%9 Journal Article
%$ pmid:31670053
%U <Go to ISI:>//WOS:000500934100003
%R 10.1016/j.ultramic.2019.112861
%U https://juser.fz-juelich.de/record/878149