Coherent Terahertz Emission Using Metasurfaces to Intercept a Flat Electron Beam

Abstract

Terahertz electromagnetic radiation is one of the hottest research topics thanks to its promising applications in diverse scientific and technological fields. Using a uniformly moving electron beam to interact with a metallic or dielectric surface is an efficient tool for the generation of high-power terahertz waves. In the present paper, we demonstrate enhanced coherent terahertz emission theoretically and experimentally by using a metasurface formed by an array of Fabry-Perot-like resonators to obliquely intercept a low-energy flat electron beam. We illustrate that the mechanism is one of modified coherent Smith-Purcell radiation rather than the expected transition radiation. More notably, this metasurface overcomes the inherent restriction imposed by the decay length in conventional beam-wave interactions, greatly enhancing the radiation efficiency and intensity. This emission promises an attractive way of developing high-power terahertz sources.