Coherent Terahertz Radiation from Patterned Sub-wavelength Holes Driven by a Free-electron Beam

We propose and investigate a coherent terahertz scheme, which uses a free-electron beam to drive a set of closely patterned sub-wavelength holes. Each hole is an independent electromagnetic resonator in the terahertz region and can emit coherent terahertz radiation. Detailed theoretical analyses are performed and the angular distributions of the radiation are obtained. We show that the proposed scheme can generate enhanced terahertz emission, which is insensitive to the moving direction of the electron beam, affording an efficient way of generating coherent terahertz radiation.