Abstract
Bound states in the continuum (BICs) have attracted much attention due to their infinite Q factor. However, the realization of the analogue of electromagnetically induced transparency (EIT) by near-field coupling with a dark BIC in metasurfaces remains challenging. Here, we propose and numerically demonstrate the realization of a high-quality factor EIT by the coupling of a bright electric dipole resonance and a dark toroidal dipole BIC in an all-dielectric double-layer metasurface. Thanks to the designed unique one-dimensional (D)–two-dimensional (2D) combination of the double-layer metasurface, the sensitivity of the EIT to the relative displacement between the two layer-structures is greatly reduced. Moreover, several designs for widely tunable EIT are proposed and discussed. We believe the proposed double-layer metasurface opens a new avenue for implementing BIC-based EIT with potential applications in filtering, sensing and other photonic devices.
Highlights
Bound States in the Continuum.The analogue of electromagnetically induced transparency (EIT) has attracted much attention since it was realized in metamaterials (MMs) [1,2,3]
Thanks for the proposed unique 1D–2D double-layer metasurface, a robust high-Q EIT is realized by near-field coupling of a bright electric dipole resonance (ED) of the disk metasurface (DMS) and a dark toroidal dipole (TD)-bound state in continuum (BIC) of the rod metasurface (RMS)
Since the TD-BIC cannot be directly excited by the normal incident wave in a singlelayer RMS, we proposed a double-layer metasurface shown in Figure 3a and demonstrated the realization of EIT by coupling a bright ED mode to the dark TD-BIC
Summary
BIC [36,37,38], which is easy to be coupled with a low-Q transverse dipole resonance, but it is very sensitive to the structural parameters of MMs. it is often difficult to eliminate the detuning between the two coupled F–W BIC and low-Q resonance in singlelayer MMs. For double-layer MMs, can the two resonances be independently designed, but the near-field coupling of them can be effectively manipulated by adjusting the relative displacement or distance of the two structures [42,43,44,45], which provides the possibility for the realization of an ideal BIC-based EIT. Thanks for the proposed unique 1D–2D double-layer metasurface, a robust high-Q EIT is realized by near-field coupling of a bright electric dipole resonance (ED) of the DMS and a dark TD-BIC of the RMS. Several methods for achieving a widely tunable EIT are discussed
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