Unveiling the orbital angular momentum and acceleration of electron beams

New forms of electron beams have been intensively investigated recently, including vortex beams carrying orbital angular momentum, as well as Airy beams propagating along a parabolic trajectory. Their traits may be harnessed for applications in materials science, electron microscopy and interferometry, and so it is important to measure their properties with ease. Here we show how one may immediately quantify these beams' parameters without need for additional fabrication or non-standard microscopic tools. Our experimental results are backed by numerical simulations and analytic derivation.Comment: 2 figures in text, 2 in supplementar

Does Guilt Affect Performance? Evidence from Penalty Kicks in Soccer

Does guilt affect performance? Exploiting a novel measure of the justification of penalty calls, we find that unjustified penalty calls negatively affect penalty conversion rates, and that this effect increases with social norms of trust. Exploiting the variance arising from players who do not play in their countries of origin by including the norms of both the league and the kickers’ countries of origin, we separate the constraints on egoism into two categories: internal sanctions, such as guilt, and external sanctions, such as shame. We find that both guilt and shame affect the performance of penalty kickers

Media 1: Arbitrary holographic spectral shaping of plasmonic broadband excitations

Originally published in Optics Letters on 01 April 2015 (ol-40-7-1615

Wavefront Shaping of Plasmonic Beams by Selective Coupling

Custom plasmonic beams are advantageous for numerous scientific and technological aspects. While plasmonic wavefront shaping had traditionally been a truly planar process, taking place on a single surface, here we explore a new method for plasmonic shaping by selectively coupling plasmonic waves between different surfaces of an insulator–metal–insulator structure. In contrast to most previous shaping techniques that rely on free-space illumination, here the plasmonic beam in the buried surface acts as the light source. We demonstrate, both experimentally and numerically, a way to tailor the amplitude and phase of the wavefront using this new technique. The proposed method can be used to efficiently shape the plasmonic beam, for potential applications in sensing, interferometry, and communications

Generation of super-oscillatory beams beyond the diffraction limit

In 1873, Ernst Abbe discovered that the imaging resolution of conventional lenses is fundamentally limited by diffraction, which, since then, has been overcome using a variety of different approaches in optical microscopy. In electron microscopy, thanks to remarkable developments in aberration corrected electron optics, the resolution of transmission electron microscopes (TEMs) and scanning TEMs (STEMs) has reached the sub-Ångström regime. However, it is still limited by instrumental stability, residual higher-order aberrations and the diffraction limit of the electron-optical system. Recently, a concept termed super-oscillation, which is analogous to the idea of super-directive antennas in the microwave community [1], was proposed [2, 3] and applied in light optics for far field imaging of sub-wavelength, barely-resolved objects beyond the diffraction limit [4]. A super-oscillating function is a band-limited function that is able to oscillate faster locally than its highest Fourier component and thereby produce an arbitrarily small spot in the far field.Here, we demonstrate experimentally for the first time a super-oscillatory electron beam whose characteristic probe size is much smaller than the Abbe diffraction limit. Figure 1(a) shows scanning electron microscopy (SEM) images of a conventional grating mask (left) and a super-oscillation off-axis hologram (right) that have the same outer diameters (10 µm). The masks were fabricated by focused ion beam milling 200-nm-thick SiN membranes coated with 150 nm Au. The masks were inserted into the C2 aperture plane of a probe-corrected FEI Titan 80-300 (S)TEM. Owing to the probe aberration corrector and relatively small numerical aperture (convergence semi-angle), diffraction-limited spots could be easily obtained from the conventional grating (Fig. 1, left), while a super-oscillatory electron probe, which was generated at the first diffraction order (Fig. 1, right), produced a much smaller hot-spot in the center. The size of the super oscillation hot-spot is approximately one third of that of the diffraction-limited spot. It could theoretically be decreased further, even below the de-Broglie wavelength of the electrons, by varying the ratio between the inner and outer radii.Further applications of such super-oscillatory electron wave functions, e.g. enhanced STEM imaging, will be presented

Visualization 1: Measurement of acceleration and orbital angular momentum of Airy beam and Airy-vortex beam by astigmatic transformation

Propagation of Astigmatic transformed Airy-Vortex beam Originally published in Optics Letters on 15 November 2015 (ol-40-22-5411

Generation of super-oscillatory electron beams beyond the diffraction limit

In 1873, Ernst Abbe discovered that the imaging resolution of conventional lenses is fundamentally limited by diffraction, which, since then, has been overcome using a variety of different approaches in optical microscopy. In electron microscopy, thanks to remarkable developments in aberration corrected electron optics, the resolution of transmission electron microscopes (TEMs) and scanning TEMs (STEMs) has reached the sub-Ångström regime. However, it is still limited by instrumental stability, residual higher-order aberrations and the diffraction limit of the electron-optical system. Recently, a concept termed super-oscillation, which is analogous to the idea of super-directive antennas in the microwave community [1], was proposed [2, 3] and applied in light optics for far field imaging of sub-wavelength, barely-resolved objects beyond the diffraction limit [4]. A super-oscillating function is a band-limited function that is able to oscillate faster locally than its highest Fourier component and thereby produce an arbitrarily small spot in the far field.Here, we demonstrate experimentally for the first time a super-oscillatory electron beam whose characteristic probe size is much smaller than the Abbe diffraction limit. Figure 1(a) shows scanning electron microscopy (SEM) images of a conventional grating mask (left) and a super-oscillation off-axis hologram (right) that have the same outer diameters (10 µm). The masks were fabricated by focused ion beam milling 200-nm-thick SiN membranes coated with 150 nm Au. The masks were inserted into the C2 aperture plane of a probe-corrected FEI Titan 80-300 (S)TEM. Owing to the probe aberration corrector and relatively small numerical aperture (convergence semi-angle), diffraction-limited spots could be easily obtained from the conventional grating (Fig. 1, left), while a super-oscillatory electron probe, which was generated at the first diffraction order (Fig. 1, right), produced a much smaller hot-spot in the center. The size of the super oscillation hot-spot is approximately one third of that of the diffraction-limited spot. It could theoretically be decreased further, even below the de-Broglie wavelength of the electrons, by varying the ratio between the inner and outer radii.Further applications of such super-oscillatory electron wave functions, e.g. enhanced STEM imaging, will be presented

Perspektiven fuer die Agrarreformpolitik Simbabwes im Lichte aethiopischer und kenianischer Erfahrungen

SIGLEBibliothek Weltwirtschaft Kiel C137341 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman