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Open AccessArticle

Tunable Bound States in the Continuum in All-Dielectric Terahertz Metasurfaces

by Xu Chen 1 and Wenhui Fan 1,2,3,*
1
State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 710119, China
2
Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
3
Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
*
Author to whom correspondence should be addressed.
Nanomaterials 2020, 10(4), 623; https://doi.org/10.3390/nano10040623
Received: 18 February 2020 / Revised: 24 March 2020 / Accepted: 25 March 2020 / Published: 27 March 2020
(This article belongs to the Section Nanophotonics: Characterization, Modelling, and Nanodevices)
In this paper, a tunable terahertz dielectric metasurfaces consisting of split gap bars in the unit cell is proposed and theoretically demonstrated, where the sharp high-quality Fano resonance can be achieved through excitation of quasi-bound states in the continuum (quasi-BIC) by breaking in-plane symmetry of the unit cell structure. With the structural asymmetry parameter decreasing and vanishing, the calculated eigenmodes spectra demonstrate the resonance changes from Fano to symmetry-protected BIC mode, and the radiative quality factors obey the inverse square law. Moreover, combining with graphene monolayer and strontium titanate materials, the quasi-BIC Fano resonance can be tuned independently, where the resonance amplitude can be tuned by adjusting the Fermi level of graphene and the resonance frequency can be tuned by controlling the temperature of strontium titanate materials. The proposed structure has numerous potential applications on tunable devices including modulators, switches, and sensors. View Full-Text
Keywords: terahertz; dielectric metasurfaces; graphene; quasi-bound states in the continuum; tunable terahertz; dielectric metasurfaces; graphene; quasi-bound states in the continuum; tunable
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Chen, X.; Fan, W. Tunable Bound States in the Continuum in All-Dielectric Terahertz Metasurfaces. Nanomaterials 2020, 10, 623.

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