Polarization-dependent electromagnetic responses of ultrathin and highly flexible asymmetric terahertz metasurfaces*

We report the polarization-dependent electromagnetic response from a series of novel terahertz (THz) metasurfaces where asymmetry is introduced through the displacement of two adjacent metallic arms separated by a distance δ. For all polarization states, the symmetric metasurface exhibits a low quality (Q) factor fundamental dipole mode. By breaking the symmetry, we experimentally observe a secondary dipole-like mode with a Q factor nearly 9x higher than the fundamental resonance. As δ increases, the fundamental dipole mode f₁ redshifts and the secondary mode f₂ blueshifts creating a highly transmissive spectral window. Polarization-dependent measurements reveal a full suppression of f₂ for all asymmetries at θ ≥ 60°. Furthermore, at δ ≥ 60 μm, we observe a polarization selective electromagnetic induced transparency (EIT) for the fundamental mode. This work paves the way for applications in filtering, sensing and slow-light devices common to other high Q factor THz metasurfaces with EIT-like response.