High-Q Fano-like resonance based on a symmetric dimer structure and its terahertz sensing application

High quality factor (Q) Fano-like resonance with intense electromagnetic confinement is essential for ultrasensitive refractive index label-free sensors. Ordinarily, planar metamaterials with asymmetric configurations are the main approaches to demonstrate these extremely narrow line-width Fano-like resonances. In this work we present a high-Q Fano-like resonance with a symmetric structure consisting of a bilayer split-ring resonator (SRR) dimer structure with identical SRR array on each layer. We find that the interference between the resonances arising from the top and bottom layers of SRR array could also give rise to Fano-like resonance with more than twenty times enhanced Q-factor (Q = 19.28) comparing to that of a single layer SRR array (Q = 0.8). The figure of merit of this Fano-like resonance (FOM = 1.79) is about ten times larger than that of the ordinary electric dipole resonance (FOM = 0.186) when applied to terahertz sensing. Our symmetric structure opens up a new way to realize the high Q Fano-like resonances, which would facilitate the design of ultrasensitive chemical and biomolecular sensing platform at terahertz frequency. (C) 2017 Optical Society of America