Fano resonance-induced high-purity circularly polarized spectra for high-precision refractive index sensing from hybrid resonator-graphene meta-surfaces.

Abstract

We demonstrate the perfect synthesis of terahertz circularly polarized Fano resonant reflecting spectra from hybrid resonator-graphene meta-surfaces for highly sensitive refractive index sensing of the biochemical analyte. Such a hybrid resonator-graphene meta-surface, consisting of periodic multi-node split ring resonators on the top of the grounded polyimide substrate inserted with a monolayer graphene sheet, can perfectly transform the linearly polarized electromagnetic fields into circularly polarized waves. Especially, the greatest polarization purity of the reflecting spectra can readily be obtained at the Fano resonance by tuning the Fermi level of the graphene, thus offering an alternative way to identify the difference between the given test specimens and other analytes with a very close refractive index on the basis of the polarization extinction ratio. The proposed methodology, capable of distinguishing the samples with a difference in the refractive index of ten thousandths, should pave the way for tangible applications of precision detections in biochemical assays with high accuracy.