Symmetry Breaking and Resonances Hybridization in Vertical Split Ring Resonator Metamaterials and the Excellent Sensing Potential

The resonances with narrow linewidths generated in metamaterials are valuable for numerous applications ranging from bio-sensing to narrow-band filter. And breaking structural symmetry of metamaterials is one of the common and efficient approaches to achieve such sharp resonances. In this paper, we present symmetry breaking introduced in vertical split ring resonators (VSRR) metamaterials to excite narrow resonance. Different from the previously reported planar asymmetric metamaterials, the three-dimensional metamaterials are dominantly excited by the magnetic field component of the terahertz illumination together with the electric component. In this case, sharp resonances with characteristic magnetic field distributions are excited. And the sharpest resonance shows up with an ultra-narrow line-width (full width at half maximum, FWHM is 5.90 GHz) and high Q of 327 at 1.93 THz. Through systematic theoretical analysis and numerical mode implementation, we reveal the sharp resonance dips are produced by resonance hybridization between a resonance mode induced by the destruction of the structural symmetry and another special resonance inherent in the symmetric VSRR metamaterials. In addition, the fabrication robustness and sensing potential of the asymmetric VSRR metamaterials are explored in this paper. The results show that the AVSRR design is insensitive to the errors in the fabrication process, like rough metal surface and smooth metal corner, but highly sensitive to the approaching substance, which prove the excellent sensing performance.