Experimental realization of a π /2 vortex mode converter for electrons using a spherical aberration corrector

Ultramicroscopy, vol. 229, pp. 113340

Abstract

In light optics, beams with orbital angular momentum (OAM) can be produced by employing a properly-tuned two-cylinder-lens arrangement, also called π/2 mode converter. It is not possible to convey this concept directly to the beam in an electron microscope due to the non-existence of cylinder lenses in commercial transmission electron microscopes (TEMs). A viable work-around are readily-available electron optical elements in the form of quadrupole lenses. In a proof-of-principle experiment in 2012, it has been shown that a single quadrupole in combination with a Hilbert phase-plate produces a spatially-confined, transient vortex mode. Here, an analogue to an optical π/2 mode converter is realized by repurposing a CEOS DCOR probe corrector in an aberration corrected TEM in a way that it resembles a dual cylinder lens using two quadrupoles. In order to verify the presence of OAM in the output beam, a fork dislocation grating is used as an OAM analyser. The possibility to use magnetic quadrupole fields instead of, e.g., prefabricated fork dislocation gratings to produce electron beams carrying OAM enhances the beam brightness by almost an order of magnitude and delivers switchable high-mode purity vortex beams without unwanted side-bands.

Authors 9

1. Thomas Schachinger corresponding

   TU Wien

   Affiliation as printed

   Institute of Solid State Physics, TU Wien, Wiedner Hauptstraße 8-10, 1040 Wien, Austria; University Service Centre for Transmission Electron Microscopy (USTEM), TU Wien, Wiedner Hauptstraße 8-10, 1040 Wien, Austria. Electronic address: thomas.schachinger@tuwien.ac.at

   Institute of Solid State Physics, TU Wien, Wiedner Hauptstraße 8-10, 1040 Wien, Austria

   University Service Centre for Transmission Electron Microscopy (USTEM), TU Wien, Wiedner Hauptstraße 8-10, 1040 Wien, Austria

2. Peter Hartel

   Corrected Electron Optical Systems (Germany)

   Affiliation as printed

   CEOS Corrected Electron Optical Systems GmbH, Englerstraße 28, 69126 Heidelberg, Germany

3. Peng‐Han Lu Aachen

   Forschungszentrum Jülich · Ernst Ruska Centre · RWTH Aachen University

   Affiliation as printed

   Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C) and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany; RWTH Aachen University, Ahornstraße 55, 52074 Aachen, Germany

   Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C) and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany

   RWTH Aachen University, Ahornstraße 55, 52074 Aachen, Germany

4. Stefan Löffler

   TU Wien

   Affiliation as printed

   University Service Centre for Transmission Electron Microscopy (USTEM), TU Wien, Wiedner Hauptstraße 8-10, 1040 Wien, Austria

5. Martin Obermair

   Karlsruhe Institute of Technology

   Affiliation as printed

   Laboratorium für Elektronenmikroskopie (LEM), Karlsruher Institut für Technologie (KIT), Engesserstraße 7, 76131 Karlsruhe, Germany

6. Manuel Dries

   Karlsruhe Institute of Technology

   Affiliation as printed

   Laboratorium für Elektronenmikroskopie (LEM), Karlsruher Institut für Technologie (KIT), Engesserstraße 7, 76131 Karlsruhe, Germany

7. Dagmar Gerthsen

   Karlsruhe Institute of Technology

   Affiliation as printed

   Laboratorium für Elektronenmikroskopie (LEM), Karlsruher Institut für Technologie (KIT), Engesserstraße 7, 76131 Karlsruhe, Germany

8. Rafal E. Dunin‐Borkowski

   Forschungszentrum Jülich · Ernst Ruska Centre

   Affiliation as printed

   Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C) and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany

9. P. Schattschneider

   TU Wien

   Affiliation as printed

   Institute of Solid State Physics, TU Wien, Wiedner Hauptstraße 8-10, 1040 Wien, Austria; University Service Centre for Transmission Electron Microscopy (USTEM), TU Wien, Wiedner Hauptstraße 8-10, 1040 Wien, Austria

   Institute of Solid State Physics, TU Wien, Wiedner Hauptstraße 8-10, 1040 Wien, Austria

   University Service Centre for Transmission Electron Microscopy (USTEM), TU Wien, Wiedner Hauptstraße 8-10, 1040 Wien, Austria