Analogue of electromagnetically induced transparency inspired by bound states in the continuum and toroidal dipolar response in all-dielectric metasurfaces

Abstract

Optical resonance cavity with high Q-factor is a paramount indicator of high-performance photonic devices. In this article, we present an all-dielectric metasurface composed of hollow cylindrical tetrameric clusters in the near-infrared region. Combining with the bound states in the continuum (BICs) theory, a distinct analogue of electromagnetically induced transparency (EIT) resonance arises. The squared inverse relationship between the Q-factor and the asymmetric parameters is calculated to corroborate the excitation of the quasi-BIC EIT pattern. By observing the distribution characteristics of the electromagnetic field in resonant mode and performing a multipole decomposition, the proposed metasurface can support magnetic dipole (MD), electric quadrupole (EQ) and toroidal dipole (TD) response simultaneously, which exhibits remarkable field confinement capability. The geometric parameters are adjusted to observe the variation of the dipole scattering energy. Subsequently, the transmission spectrum shows a peculiar pair of TD resonances, which possess remarkably dependence on polarization. The sensitivity and figure of merit (FOM) values of the sensor can reach 430 nm/RIU and 483 RIU−1. It is believed that the proposed metasurface may provide a constructive approach for slow light devices, high-performance sensors and polarization independent devices.