Tuning Fano resonances in a planar metamaterial

We demonstrate the tuning of Fano resonances in a symmetric planar metamaterial both experimentally and theoretically, on the basis of a unit cell consisting of two identical split ring resonators. The electromagnetic responses of the planar metamaterial to incident TE and TM waves are measured. By controlling the excitation of the Fano-type trapped-mode resonance via the angle of incidence, the resonance can be switched on/off and the resonance is red-shifted by up to 21%. Based on the finite element method, the field distributions are presented and a very sharp normal phase dispersion renders the response of the structure a metamaterial analog of classical electromagnetically-induced transparency (EIT). The simulated results are in good agreement with the measured ones. The switching feature of the trapped mode resonance in symmetric metamaterial can provide an easy approach to tuning the performance of metamaterial.