Free-Electron Exciting and Steering of the Radiation From Surface Plasmons on Nanowire Array

The radiation from surface plasmons (SPs) on nanowire (NW) array excited by free electron is attractive for its coherence and tunability. Yet previously, only 2D model had been considered. Here, we explore a realistic 3D model of free electron exciting NW array. Multiple SPs modes on the NWs are excited, which can radiate in both the radial and axial directions. Based on the axial radiation, a modified Smith-Purcell radiation in the plane parallel to the free electron is demonstrated. The radiation can be controllably steered in any directions in that plane, which indicates the possibility for developing the on-chip nano-scale light-sources and devices.