Efficient Measurement of the Orbital-Angular-Momentum Spectrum of an Electron Beam via a Dammann Vortex Grating

Measuring the orbital-angular-momentum (OAM) states of electron beams is of great importance in diverse applications. Here, we demonstrate a method to effectively measure the OAM spectrum of an electron beam by exploiting a two-dimensional Dammann vortex grating (DVG). This grating enables us to simultaneously measure an input electron beam in a transmission electron microscope using its OAM components with values between -10 (h) over bar and 10 (h) over bar (OAM spectrum). We then experimentally evaluate the performance of the DVG OAM analyzer when measuring electron beams generated by spiral zone plates and nanofabricated magnetic needles. Our evaluation supports the validity of this approach, which paves the way toward enabling a wide range of electron OAM applications, including in nanoscale imaging and in materials science.