Ultramicro-sensing of terahertz metamaterials using sample traps

A metamaterial sensor using sample traps based on terahertz electromagnetically-induced-transparency-like（EIT-like） effect is proposed. The basic unit structure of the sensor is composed of a metal wire and a pair of split-ring resonators(SRRs), which are coupled to produce EIT-like effect. A transparency peak with a full width at half maximum (FWHM) of 178 GHz is obtained at 1.067 THz, and the maximum transmittance of the transparency peak is 89.71%. The sensing characteristics of the structure are studied, and the sensitivity is 178 GHz/(RIU·mm3). It is found that the electric field at gaps of the SRRs on both sides is the strongest by analyzing electric field distribution at the resonant frequency point of the metamaterial. Sample traps are constructed at the gaps, where the electric field is strongest. The photoresist was filled into the sample traps as the object to be measured, and 50 GHz frequency offset was successfully measured, which verified that the sample trap structure can be applied to sensing. After research and analysis, by placing samples in the sample traps, the sample volume is reduced to the ultra-micro level, and the sensitivity is increased to 5538 GHz/(RIU·mm3), which is 31 times higher than before. The successful identification of water, human skin and rat skin samples shows that the metamaterial sensor using sample traps has potential application value in the field of ultra-micro detection.