Gyromagnetically Induced Transparency of Meta-Surfaces

We demonstrate that the violation of the time-reversal (TR) symmetry in the presence of a gyromagnetic substrate can produce an analog of electromagnetically induced transparency in metallic meta-molecules. The simplest implementation of such gyromagnetically induced transparency (GIT) in a meta-surface comprised of an array of resonant antenna pairs placed on a gyromagnetic substrate and illuminated by a normally incident electromagnetic wave is analyzed. TR symmetry breaking introduced by the magnetic field makes meta-molecules bi-anisotropic and causes spectrally-sharp Fano interference between the otherwise uncoupled electric and magnetic dipolar resonances of the meta-molecules. The applied magnetic field results in a sharp transmission peak through the otherwise reflective meta-surface. We show that, for oblique wave incidence, one-way GIT can be achieved by the combination of spatial dispersion and TR symmetry breaking. These theoretically predicted phenomena pave the way to non-reciprocal switches and isolators that can be dynamically controlled by electric currents.