Terahertz metamaterial filter with enhanced sensing sensitivity using the suspended structure design

This paper presents a method to improve refractive index sensing sensitivity using a suspended structure design with a suspended silver split ring resonator metamaterial structure on a silica substrate, which is important in improving detection sensitivity compared to a planar structure. Its basic unit has two metal cleavage rings attached back-to-back to an etched dielectric substrate. Due to the enhancement of the electric field around the gap of the surface-modularized metal structure and the expansion effect of the electric field of the etched layer, the sensitivity is enhanced from 162.5 GHz/RIU of the planar structure to 342.5 GHz/RIU with a sensing sensitivity enhancement factor of 2.1 times compared to the planar metamaterial with an unetched substrate. When the refractive index of the surrounding environment is changed from n = 1 to n = 1.4, the resonance center produces 0.137 THz redshift. Based on this, a more practical structural design is proposed to improve the refractive index sensing sensitivity while reducing the fabrication difficulty. This work provides new ideas for the research of terahertz (THz) metamaterials with high refractive index sensitivity and offers more device options for THz sensing applications.