Free-Electron-Driven Multi-Frequency Terahertz Radiation on a Super-Grating Structure

Juan-Feng Zhu,Pu-Kun Liu,Chao-Hai Du,Fan-Hong Li,Lu-Yao Bao

doi:10.1109/access.2019.2938270

Juan-Feng Zhu, Pu-Kun Liu + Show 3 more

Open Access

https://doi.org/10.1109/access.2019.2938270

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Abstract

A free-electron-driven multi-frequency terahertz (THz) radiation based on a super-grating structure is elucidated in this paper. The super-grating, i.e., periodically depth-modulated metallic grating, has a peculiar dispersion characteristic, similar to the energy bands in a crystal due to the Brillouin zone folding effect. The multi-frequency radiation is stimulated in several directions with the excitation of a free electron as the synchronization points are in the radiative region. The radiation frequency can be independently tuned by the groove depths of the super-grating. The number of frequencies is tailored by the modulated period. Additionally, the multi-frequency THz radiation exhibits a frequency-locked effect during the energy variation of the free electron. Moreover, the radiation field intensity shows a significant enhancement compared with that of a conventional Smith-Purcell radiation. The work is promising for developing efficient on-chip THz radiation sources and boosts advanced THz applications such as communications, multi-frequency imaging, and beam diagnostics, etc.

Highlights

Terahertz (THz) sources play a key role in promoting the development of THz technologies [1]–[3]
Despite the coherent THz radiation based on the spoof surface plasmon (SSP) wave can be obtained from the beam-SSP interaction, the SSP is confined at the surface of grating as its wavenumber is considerably larger than that of propagation wave [13], [14]
As the super-grating can be equivalent to a series of SSP cavities, the multi-frequency THz radiation exhibits a frequency-locked effect during the dynamic voltage tuning of free electron owing to the resonance characteristic in these cavities

Summary

INTRODUCTION

Terahertz (THz) sources play a key role in promoting the development of THz technologies [1]–[3]. THz radiation sources based on the beam-wave interaction between the free electron and SSP wave have been fully investigated. A free-electron-driven multi-frequency THz radiation is achieved based on a super-grating. Zhu et al.: Free-Electron-Driven Multi-Frequency THz Radiation on a Super-Grating Structure bands in a crystal due to the Brillouin zone folding effect. In this manner, part of the dispersion curve is folded into the radiative region. As the super-grating can be equivalent to a series of SSP cavities, the multi-frequency THz radiation exhibits a frequency-locked effect during the dynamic voltage tuning of free electron owing to the resonance characteristic in these cavities. The multi-frequency radiation provides a new way for developing on-chip THz radiation sources and holds promises in various advanced THz applications

MODEL PRESENTATION

DISSCUSSION

CONCLUSION