Terahertz Biosensing Based on a Polarization-Insensitive Metamaterial

A polarization-insensitive metamaterial biosensor composed of metallic square ring resonators is proposed and is shown to be especially suitable to work together with the linear polarized femtosecond laser pumped terahertz time-domain spectroscopy. A symmetric slit is distributed on every side of the ring to render the biosensor insensitive to the polarization direction of the incident terahertz wave. The proposed structure is analyzed with the finite-element method and investigated experimentally. The results reveal that a minimal resolution of 17.7 μmol/L in the detection of bovine serum albumin is obtained when the biosensor is oriented arbitrarily in the plane containing the electric field vector.