LAUSR

Abstract Terahertz (THz) metamaterials and their assemblies with strong Fano resonance are of fundamental interest and have potential applications in modulators, slow-light devices and THz sensing. Here, we demonstrate that near-field coupling dominated Fano-dip and plasmon-induced transparency can be simultaneously generated in a THz metamaterial by introducing a symmetry-breaking nanogap. We fabricated the designed metamaterials THz structures using our lately developed “sketch and peel” lithography process, which can obtain the multi-scale micro/nano-structures with small gap size and high fabricating efficiency. Both experimental and numerically simulated spectra show that the physical origin of Fano dip and plasmon-induced transparency are the near-field coupling derived destructive interference between two overlap plasmon resonance modes, and their specific manifestation depends on the coupling intensity between two overlapped plasmon modes. Enabled by the strong near field in the THz nanogaps, the numerical results show that the refractive index sensitivity of Fano dip and plasmon-induced transparency can be as high as 153 GHz/RIU and 236 GHz/RIU with a 500 nm small feature size, respectively. Our study not only provides an insight to understand the different spectral manifestation of Fano resonance in THz metamaterials, but also a possible straightforward path to achieve ultra-sensitive micro/nano-scale THz refractive index sensing.