Bound states in the continuum driven by multiple modes for high Q refractive index sensing in metasurfaces

• Published in: Journal of physics. D, Applied physics Vol. 56; no. 46; pp. 465101 - 465109
• Main Authors: Li, Jiangbin, Wang, Zhihui, Liu, Haiying
• Format: Journal Article
• Language: English
• Published: IOP Publishing 16.11.2023
• Subjects: factor; figure of merit; Freidrich–Wintgen BIC; symmetry-protected BIC
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/1361-6463/acedbc

Bound states in the continuum (BICs) have attracted much attention in the field of refractive index sensing. In this paper, we propose multi-mode symmetry-protected BICs (SP-BICs) and the Freidrich–Wintgen BIC (FW-BIC) in terahertz metasurfaces consisted of periodic open split ring resonators. Firstly, multi-mode SP-BICs are subject to the magnetic dipole, electric dipole (ED), and toroidal dipole (TD) modes. Moreover, we demonstrate the FW-BIC by strongly coupling the electric quadrupole and TD modes. For micron film sensing of the ED mode, simulation results show that the Q factor, the sensitivity of sensing ( S ), and the corresponding figure of merit can simultaneously reach 1561, 141 GHz/RIU, and 306, respectively. Our quasi-BICs have potential applications in micro-sensing.