摘要: Free-electron radiation results from the interaction between swift electrons
and the local electromagnetic environment. Recent advances in material
technologies provide powerful tools to control light emission from free
electrons and may facilitate many intriguing applications of free-electron
radiation in particle detections, lasers, quantum information processing, etc.
Here, we provide a brief overview on the recent theoretical developments and
experimental observations of spontaneous free-electron radiation in various
structured environments, including two-dimensional materials, metasurfaces,
metamaterials, and photonic crystals. We also report on research progresses on
the stimulated free-electron radiation that results from the interaction
between free electrons and photonic quasi-particles induced by the external
field. Moreover, we provide an outlook of potential research directions for
this vigorous realm of free-electron radiation.