Metallic meshes as biochemistry sensor chip in the terahertz region

A biological sensor based on the resonant transmission characteristics of metal meshes has been proposed in the terahertz (THz) region. We simulated THz transmission characteristics of two kinds of structure by FDTD method: arrays of circular hole and rectangular hole. Their resonant frequencies at the interface of metal and air are 1.42THz and 1.225THz respectively. We find that the refractive index and thickness of the sample commonly affect the surface plasma's resonant frequency. When coupled with a layer of sample of 50 micron on the metallic meshes, the resonance frequency would shift to a lower frequency with an increasing refractive index. Sensitivity of two kinds of structure is 0.64 THz/RIU and 0.507 THz/RIU respectively. The sensitivity differences of two kinds of structure lie mainly in the different dominant resonant transmission mechanism. The thickness also affected detection sensitivity. When thickness of sample is less than the corresponding resonance wavelength, we need to consider the influence of thickness. This theoretical simulation can be good reference for the following experiment.