Sensitive refractive index sensing with tunable sensing range and good operation angle-polarization-tolerance using graphene concentric ring arrays

A highly tunable refractive index sensor with excellent performance and good operation angle-polarization-tolerance is proposed and demonstrated numerically by means of the finite element method. The proposed sensor consists of a planar regular array of paired graphene concentric ring resonators sandwiched between a substrate and a sensing medium. Numerical calculation results show that a high sensitivity of 9.59 mu m per refractive index unit and figure of merit of 5.82 can be reached for lower sensing medium refractive indices. The introduction of graphene in this sensor can enhance the absorption of biomolecules and make the sensing range actively tunable. Therefore, it can be conveniently used for possible detection of the refractive index variation of gases, liquids or mixed solutions. Also, we predict that a multi-channel sensor can be achieved by introducing several graphene concentric ring resonators into each unit cell of the array.