High-sensitivity refractive index sensors using coherent perfect absorption on graphene in the Vis-NIR region

Plasmonic structures with sophisticated nanofabrication have revolutionized the ability to trap light on the nanoscale and enable high-sensitivity refractive index sensing. Previous theoretical research has indicated that the sensitivity and figure of merit around the wavelength of 1 μm for a plasmonic sensing system can be up to 13000 nm/RIU and 138, respectively. In order to improve the sensing performance, we propose a graphene-based nonplasmonic sensor with the sensitivity over 440000 nm/RIU at the wavelength of 1 μm, which is 33 times more than the theoretical result of plasmonic sensors. Our graphene sensor is a nanofabrication-free design with perfect light confinement within a monolayer of graphene. Meanwhile, its figure of merit is up to the scale of thousands, which is also much higher than plasmonic sensors. Our scheme uses a simple dielectric structure with a monolayer of graphene and shows a great potential for low-cost sensing with high performance.