Highly Q-factor refractive index sensor based on graphene stack

Abstract

The perfect absorber with high figure of merit (FOM) and sensitivity for mid-infrared application is developed in this study. The structure contains a nanoaperture as a resonator and multi-layer hyperbolic metamaterial of graphene-SiN is place under the nanoaperture to increasing the absorption. The results show how the chemical potential of graphene can improve the absorbance. Finally, a coat of SiO2 is pinpointed over the nanoaperture for enhance the absorption and protecting the surface. The proposed aperture is designed symmetrically based on crossed shape to reduce the polarization effects on sensing. The Q-factor has increased sharply to 3000 for the final device by utilizing the hyperbolic material structure. The left-hand characteristic of the hyperbolic metamaterial provides a condition for concentrating the surface Plasmon’s at the interface of the gold layer with the substrate, leading to the reflection reduction to − 46 dB. This absorber is considered as an optical sensor for various materials under test (MUT) in the optical spectrum and it is simulated by FIT method as a time-domain technique. This sensor has a sensitivity of 400 nm/RIU and the FOM of 89000 RIU−1.