Generation of Perfect Electron Vortex Beam with a Customized Beam Size Independent of Orbital Angular Momentum

Abstract

The electron vortex beam (EVB)-carrying quantized orbital angular momentum (OAM) plays an essential role in a series of fundamental research. However, the radius of the transverse intensity profile of a doughnut-shaped EVB strongly depends on the topological charge of the OAM, impeding its wide applications in electron microscopy. Inspired by the perfect vortex in optics, herein, we demonstrate a perfect electron vortex beam (PEVB), which completely unlocks the constraint between the beam size and the beam’s OAM. We design nanoscale holograms to generate PEVBs carrying different quanta of OAM but exhibiting almost the same beam size. Furthermore, we show that the beam size of the PEVB can be readily controlled by only modifying the design parameters of the hologram. The generation of PEVB with a customized beam size independent of the OAM can promote various in situ applications of free electrons carrying OAM in electron microscopy.

Monocular Metasurface for Structured Light Generation and 3D Imaging with a Large Field-of-View

“…Various intriguing optical phenomena and laws have been discovered, including extraordinary Young’s interference, generalized refractive and reflective law, generalized Fresnel formulas, asymmetric spin–orbit interaction, and generalized geometric phase . Since the subwavelength structural inclusions can implement independent phase, amplitude, and polarization modulation, enhanced, multifunctional, or even totally new functionalities can be realized, including vector vortex beam generation and determination, − wide-FOV planar beam scanning and imaging . In the field of imaging, researchers have utilized metasurfaces to achieve functionalities such as underwater binocular sensing and intelligent depth perception. − Within the realm of structured light imaging, there is an increasing interest of researchers in using a metasurface to achieve comprehensive space coverage by leveraging its subwavelength-scale unit cells, far surpassing the DOE counterpart.…”

“…Recently, the emergence of the optical metasurface, − a kind of digitally structured material composed of subwavelength-spaced thin elements, greatly advances the development of digital optics by downscaling the pixel sizes of the structural inclusions to the subwavelength scale, which enables us to overcome the bottlenecks of conventional optics . Various intriguing optical phenomena and laws have been discovered, including extraordinary Young’s interference, generalized refractive and reflective law, generalized Fresnel formulas, asymmetric spin–orbit interaction, and generalized geometric phase .…”