We propose an improved type of holographic-plate suitable for the shaping of electron beams. The plate is fabricated by a focused ion beam on a silicon nitride membrane and introduces a controllable phase shift to the electron wavefunction. We adopted the optimal blazed-profile design for the phase hologram, which results in the generation of highly efficient (25%) electron vortex beams. This approach paves the route towards applications in nano-scale imaging and materials science

The study of structured optical waves has enhanced our understanding of light and numerous experimental methods now enable the control of the angular momentum and radial distributions. Recently, these wavestructuring techniques have been successfully applied to the generation and shaping of electron beams, leading to promising practical and fundamental advances. Here, we discuss recent progress in the emerging field of electron beam shaping, and explore the unique attributes that distinguish electron beams from their photonic analogues

Electron waves that carry orbital angular momentum (OAM) are characterized by a quantized and unbounded magnetic dipole moment parallel to their propagation direction. When interacting with magnetic materials, the wavefunctions of such electrons are inherently modified. Such variations therefore motivate the need to analyse electron wavefunctions, especially their wavefronts, to obtain information regarding the material's structure. Here, we propose, design and demonstrate the performance of a device based on nanoscale holograms for measuring an electron's OAM components by spatially separating them. We sort pure and superposed OAM states of electrons with OAM values of between −10 and 10. We employ the device to analyse the OAM spectrum of electrons that have been affected by a micron-scale magnetic dipole, thus establishing that our sorter can be an instrument for nanoscale magnetic spectroscopy.

Free electrons can possess an intrinsic orbital angular momentum, similar to those in an electron cloud, upon free-space propagation. The wavefront corresponding to the electron's wavefunction forms a helical structure with a number of twists given by the angular speed. Beams with a high number of twists are of particular interest because they carry a high magnetic moment about the propagation axis. Among several different techniques, electron holography seems to be a promising approach to shape a conventional electron beam into a helical form with large values of angular momentum. Here, we propose and manufacture a nano-fabricated phase hologram for generating a beam of this kind with an orbital angular momentum up to 200 . Based on a novel technique the value of orbital angular momentum of the generated beam are measured, then compared with simulations. Our work, apart from the technological achievements, may lead to a way of generating electron beams with a high quanta of magnetic moment along the propagation direction, and thus may be used in the study of the magnetic properties of materials and for manipulating nano-particles.Almost a century ago Rutherford and Bohr proposed a model, the so-called Bohr model, to describe the structure of atoms in which model atoms consist of a positive nucleus surrounded by orbiting electrons [1, 2]. Even in this semiclassical model, orbiting electrons possess a quantized orbital motion, i.e. orbital angular momentum (OAM). This quantization, indeed, lies at the heart of the rotationally symmetric nature of the atom. However, it took quite a long time to theoretically predict and experimentally demonstrate that free electrons can also carry a quantized OAM value upon freespace propagation [3][4][5]. The wavefront of electrons carrying a quantized OAM forms a helical shape exp (imϕ) with an integer winding index m, where ϕ is the azimuthal angle in polar coordinates. A free electron with such a helical phasefront possesses an OAM value of m along the propagation direction, and has a magnetic moment µ OAM = mµ B oriented along the beam axis with a polarity that depends on the sign of m. µ B = e /(2m e ) is the Bohr magneton of the electron, is the Planck constant, e and m e are the electron charge and rest mass, respectively. This magnetic moment, unlike the spin Bohr magneton, in principle is unbounded and can be large if desired. Nonetheless, it is bounded by the accuracy of phase modulation and the numerical aperture of the electron optics [6]. The spatial density distribution of these electrons in the transverse plane -orthogonal to propagation directionappears to be a doughnut shape, because a helical phase is undefined at the origin. Moreover, the current density associated with the wavefunction of "twisted" electrons circulates about the origin; thus, these beams are also called electron vortex beams (EVBs). Twisted electron beam (EBs) possess a novel magnetic moment µ OAM along the propagation axis, and thus found immediate applications in the study of materials [7,8]...