Ultra-high figure of merit refractive index sensor based on concentric ring and disk resonator

A plasmonic refractive index sensor based on metal–insulator–metal (MIM) waveguide coupled with concentric ring and disk resonator (CRDR) is proposed in this work. The plasmonic refractive index sensor with a sensitivity of 1039 nm/RIU and a high figure of merit (FOM) of 401 in the near-infrared region is numerically investigated using a finite element method (FEM). The physical mechanism of high Q factor of the mode of CRDR can be explained by the coupled mode theory. The structural parameters of the plasmonic sensor are also discussed. The structural parameters can be changed to adjust the sensor properties. Furthermore, the application of proposed plasmonic sensor in bio-sensing is analyzed.