FREE-ELECTRON RADIATION ENGINEERING VIA STRUCTURED ENVIRONMENTS

|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 the research progresses on the stimulated free-electron radiation that results from the interaction between free electrons and photonic quasi-particles induced by the external (cid:12)eld. Moreover, we provide an outlook of potential research directions for this vigorous realm of free-electron radiation. tailorable emission properties, free-electron radiations broad applications in the of particle