Chiral Smith-Purcell Radiation Light Source

Smith-Purcell radiation (SPR) with broadly tunable spectra has attracted attention in light emission, and this free-electron-driven source shows great potential in illumination fields, such as terahertz sources, ultra-compact light sources, free-electron lasers, etc. However, it remains difficult to control the polarization properties of SPR and realize a free-electron chiral light source. In this work, the chiral SPR with the maximum chirality (>40%) is acquired in a periodic stacked nanosquare light-well, and the radiation chirality is manipulated by variations of the designed electron beam excitation positions. Furthermore, this work reveals that the chiroptical effect originates in the superposition of SPRs with different phases and polarization, which are derived from adjacent sidewalls. This work may deepen the comprehension of electron-matter interaction and facilitate the development of compact electron-driven chirality-tunable source-on-chip, highlighting potential applications in photonic integration and binary data processing.