Symmetric and asymmetric Fano resonances in a broken axial symmetry metasurface of split ring resonators

Abstract

In the paper, a metasurface is investigated, the unit cell of which consists of two resonators. We show that the breaking of the axial symmetry of the unit cell in such a structure leads to the appearance of two Fano resonances instead of one that is characteristic of the symmetric unit cell. The two resonances are different, one of which is symmetric and the other is asymmetric. This is confirmed by calculating the phases of currents in the adjacent resonators. Modeling results are confirmed by experimental investigation of the metasurface spectrum in a microwave frequency range showing two resonances measured experimentally. A detailed study of the currents flowing in the adjacent resonators of the unit cell demonstrates that currents at the Fano resonance dips flow either in phase or in antiphase with respect to the external electric field, whereas in peaks this difference is π/2. This confirms the interference nature of the Fano effect.