Abstract-Efficient terahertz and infrared Smith–Purcell radiation from metal-slot metasurfaces

Yanan Song, Jiayuan Du, Ningxiao Jiang, Liu Liu, and Xinhua Hu

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-43-16-3858

We demonstrate that when a charged particle moves on top of a metal-slot metasurface consisting of metallic slot resonators, strong Smith–Purcell electromagnetic (EM) radiation can be produced at resonant frequency. By adjusting the period of the metasurface, the resonant (or working) frequency can be tuned from gigahertz to terahertz and infrared regions. Since the EM field is localized in the slots rather than at the metal surface, the metasurfaces are found to exhibit a very low absorption loss ratio (<1%$<1\%$) in low working frequencies (<1  THz$<1\mathrm{THz}$). Although it becomes larger in high frequencies (>1  THz$>1\mathrm{THz}$), the loss ratio remains relatively low (<12%$<12\%$). In addition, a nonlinear relationship is also uncovered between the resonant frequency and the reciprocal of the period. Our results could benefit the construction of efficient, compact terahertz, and infrared free-electron light sources.

© 2018 Optical Society of America

Abstract-Terahertz and infrared Smith-Purcell radiation from Babinet metasurfaces: Loss and efficiency

Liu Liu, Huiting Chang, Chi Zhang, Yanan Song, and Xinhua Hu

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.96.165435

When a charged particle moves close and parallel to the surface of a Babinet metasurface composed of metallic $C$-aperture resonators, strong electromagnetic radiation arises at resonant frequency. Here we systematically study the Smith-Purcell effects in Babinet metasurfaces with different periods. By tuning the period, the resonant (or working) frequency of the metasurface can vary from GHz to THz and infrared ranges. It is found that for working frequencies lower than 10 GHz, the ratio of absorption loss to input power is about 3.7%. Although the loss ratio increases with increasing working frequency, it remains as low as 11% (29%) at a working frequency of 10 THz (224 THz). Due to the existence of loss, a nonlinear relationship is also found between resonant frequency and the reciprocal of period. Our results suggest that Babinet metasurfaces could be a good candidate for fabricating efficient, compact THz and infrared free-electron light sources.

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Abstract-Tunable terahertz radiation from graphene induced by moving electrons

Phys. Rev. B 89, 245434 – Published 20 June 2014

Tianrong Zhan, Dezhuan Han, Xinhua Hu, Xiaohan Liu, Siu-Tat Chui, and Jian Zi

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.245434

Based on a structure consisting of a single graphene layer situated on periodic dielectric gratings, we show theoretically that terahertz radiation can be generated by low-energy electron bunches moving atop the graphene layer. The THz emission arises from graphene plasmons excited efficiently by the moving electrons. We find that the radiation intensity can be strongly enhanced due to the local field enhancement of graphene plasmons arising from their low losses and high confinement. Importantly, the radiation frequency can be tuned over a wide spectral range by varying the Fermi level of the graphene layer. Our results could find applications in developing tunable and miniature free-electron terahertz radiation sources.

DOI: http://dx.doi.org/10.1103/PhysRevB.89.245434

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