Trapped-mode resonances in all-metallic metasurfaces comprising rectangular-hole dimers with broken symmetry

Abstract

Traditional metamaterial systems usually own a low Q factor due to the strong absorption and radiation loss. Fano resonances in ultrathin metasurfaces provide an efficient method for solving the issue. In this work, we theoretically and experimentally study the trapped-mode resonance in rectangular-hole dimers with broken symmetry. Compared to the asymmetric particle dimers that have been widely investigated, the asymmetric hole dimers in freestanding metal screens present an all-metallic platform for engineering the high-Q resonances. With the experiments, a significantly increased Q factor of ∼200 has been achieved in the microwave region. Numerical simulations show that, in comparison with the incident field, the hole electric field (and intensity) can be increased by ∼127 times (and ∼16 000 times). Moreover, the evolution characteristic of the trapped-mode resonance with the structural parameters has been studied systematically. The inversely quadratic relationship between the Q factor and asymmetric parameter, proposed primarily for the particle dimers [Koshelev et al., Phys. Rev. Lett. 121, 193903 (2018)], is found to work well for the asymmetric hole dimers.