A Terahertz Metasurface for Thin Film Biosensing

Abstract

Terahertz (THz) metasurface biosensors have attracted considerable attention in thin-film biological sensing due to their real-time and ultra-sensitive detection properties. This paper proposes a planar array of split-ring resonators (SRRs) over a dielectric substrate to study its performance for having a highly sensitive, non-label, and low-cost biosensor. By coupling the two SRRs of each unit cell, a pick in the transmission spectra occurs at 1.58 THz. Analyzing the electromagnetic field distribution and surface current flow shows the appearance of coupled electric and magnetic dipoles in the resonators. It is also shown that changing the distance between the coupled SRRs can passively tune the resonance frequency. Finally, the sensing functionality of the metamaterial is validated by simulating a human skin tissue with a refractive index of 1.6 and a thin thickness of $6\ \mu\mathrm{m}$. The results give a remarkable theoretical sensitivity of 400 GHz/RIU.