Cylindrical Metalens for Generation and Focusing of Free-Electron Radiation

Aviv Karnieli, Dolev Roitman, Matthias Liebtrau, Shai Tsesses, Nika Van Nielen, Ido Kaminer, Ady Arie, Albert Polman

Research output: Contribution to journalArticlepeer-review

Abstract

Metasurfaces constitute a powerful approach to generate and control light by engineering optical material properties at the subwavelength scale. Recently, this concept was applied to manipulate free-electron radiation phenomena, rendering versatile light sources with unique functionalities. In this Letter, we experimentally demonstrate spectral and angular control over coherent light emission by metasurfaces that interact with free-electrons under grazing incidence. Specifically, we study metalenses based on chirped metagratings that simultaneously emit and shape Smith-Purcell radiation in the visible and near-infrared spectral regime. In good agreement with theory, we observe the far-field signatures of strongly convergent and divergent cylindrical radiation wavefronts using in situ hyperspectral angle-resolved light detection in a scanning electron microscope. Furthermore, we theoretically explore simultaneous control over the polarization and wavefront of Smith-Purcell radiation via a split-ring-resonator metasurface, enabling tunable operation by spatially selective mode excitation at nanometer resolution. Our work highlights the potential of merging metasurfaces with free-electron excitations for versatile and highly tunable radiation sources in wide-ranging spectral regimes.

Original languageEnglish
Pages (from-to)5641-5650
Number of pages10
JournalNano Letters
Volume22
Issue number14
DOIs
StatePublished - 27 Jul 2022

Keywords

  • Smith-Purcell radiation
  • cathodoluminescence
  • free electrons
  • metalens
  • metasurfaces
  • nanophotonics
  • wavefront shaping

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