Excitation and Dynamic Tuning of High- Q Resonances with Electromagnetic Coupling Asymmetry

Abstract

Metasurfaces with in-plane structure asymmetry have been widely explored for realizing high-Q resonances. However, the structure asymmetry parameter, which governs the magnitude of the Q factor, is difficult to modulate directly. This hinders the Q factor from being tuned actively and efficiently. In this paper, a mechanism to excite the high-Q resonance in the in-plane symmetric hole lattice is proposed. The resonance is achieved by use of two perforated metasurfaces, where two localized modes in one layer couple differently with a third mode in the other layer, exhibiting an interplane coupling asymmetry. We further show that, by lateral displacement of one metasurface (approximately \ensuremath{\lambda}/20), the electromagnetic coupling asymmetry can be manipulated. The high-Q resonance can thus be switched on or off and tuned dynamically, leading to efficient modulation of the transmission intensity, the Q factor, etc. The results open a way for excitation and dynamic tuning of the high-Q resonance.