Abstract
We report an approach to efficiently generate terahertz radiation from a combined periodic structure. The proposed configuration is composed of two metallic slit arrays deliberately designed with different periodic length, slit width and depth. We found that the combination of the two slit arrays could provide special electromagnetic modes, which exhibit nonradiative property above the surface of one slit array and radiative property inside the other one. An electron beam holding proper energy could resonate with those modes to generate strong and directional electromagnetic radiations in the terahertz regime, indicating that the approach has the potential in developing high-performance terahertz radiation sources.
Highlights
There is continued interest in developing terahertz radiation sources[1,2,3,4,5,6,7,8,9,10,11,12,13,14] to meet various requirements of increasing applications[15,16,17,18] in scientific and industrial fields
The traditional electron-beam-driven devices, such as backward-wave oscillators, traveling-wave tubes and Smith-Purcell free-electron lasers, are usually considered to be high-power, continuous wave and compact terahertz radiation sources, and attempts are still being made to increase the average power, extend the frequency regime and improve the output performance. In such kind of devices the electron beam with medium energy is used to interact with the surface wave generated from a metallic periodic structure
The surface wave is a kind of nonradiative electromagnetic modes, which propagates along the surface of the structure, and it radiates only at the ends of the structure by the diffraction effect
Summary
There is continued interest in developing terahertz radiation sources[1,2,3,4,5,6,7,8,9,10,11,12,13,14] to meet various requirements of increasing applications[15,16,17,18] in scientific and industrial fields. In order to correspond to the radiation angle in sub-wavelength slit array, the refractive index of an effective dielectric medium is derived as nef = c/v cos(arctan(v/c)), which relates to the electron’s velocity.
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