Intensive vertical orientation Smith-Purcell radiation from the 2D well-array metasurface.

We present an intensive vertical orientation Smith-Purcell radiation with the 2D well-array metasurface. It is shown that the moving electrons can induce three induced surface currents at the well-array metasurface, where a strong coupling among them takes place. The coupling significantly improves the radiated field intensity and shapes the radiation angle-distribution. The theoretical results show that the Smith-Purcell radiation's field intensity is 3 times larger than the one within a conventional grating structure with directional radiation at 90 degree. Therefore, much stronger intensity and more centralized directional radiation will provide a promising way to develop electron beam driven THz sources.