Trapped mode resonances in symmetric rectangular-hole tetramers

Abstract

High Q-factor trapped mode resonances are mostly supported by weakly asymmetric metamolecules. In this paper, we study theoretically and experimentally a planar all-metallic metamaterial comprising highly symmetric metamolecules (rectangular-hole tetramers in a freestanding metallic plate) and find that high Q-factor trapped mode resonances can also be realized. The effect comes from the destructive interference between two anti-phased excitations: the electric dipole modes of the two inner and two outer rectangular holes within individual tetramers. Here, the high Q-factor resonance is dominated by the hole separation that affects greatly the coupling and radiation. At the resonance, a huge enhancement of electric field in each hole appears, accompanied by a significant slow-wave effect in the reflection process. Our design has potential applications in constructing high Q-factor filters, highly sensitive sensors and slow-wave devices.