Abstract

We introduce a metasurface capable of generating multiple bound states in the continuum (BICs). Through the rotation of two ${{\rm LiTaO}_3}$ columns, the symmetry protection can be broken, resulting in a quasi-BIC with a high quality factor. The multipolar analysis of each BIC confirms that the dominant pole aligns closely with the electromagnetic field. Additionally, we demonstrate the tunability of the quasi-BIC’s quality factor by modifying the Fermi level of graphene, designing a terahertz (THz)-wave modulator with a remarkable modulation depth more than 90% and a modulation range of 36 meV, 108 meV, 30 meV, 1.2 meV, and 42 meV. Furthermore, the sensing performance of the metasurface is investigated. The sensitivity of peak1 is measured at 0.41 THz/RIU, peak2 at 0.4 THz/RIU, peak3 at 1.049 THz/RIU, peak4 at 0.34 THz/RIU, and peak5 at 1.59 THz/RIU, and the figure of merit of these BICs is calculated as ${455.56} \; {{\rm RIU}^{- 1}}$, ${62.8} \; {{\rm RIU}^{- 1}}$, ${11},{655.56} \; {{\rm RIU}^{- 1}}$, ${17,\!000} \; {{\rm RIU}^{- 1}}$, and ${7,\!950} \; {{\rm RIU}^{- 1}}$, respectively. Compared with relevant studies, our metasurface demonstrates excellent performance. The results of these studies have potential applications in sensing, optical communication, and energy harvesting, and open up possibilities for efficient control and manipulation of terahertz waves.

© 2023 Optica Publishing Group

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