A nano-refractive index sensor based on a MIM waveguide with a semicircular ring rectangular resonator

This paper proposes a novel nano-sensor structure consisting of the metal-insulator-metal (MIM) waveguide with two rectangular baffles and a semicircular ring rectangular resonator (SRRR). The sensor's transmission characteristics are investigated using the finite-difference time-domain (FDTD) method. The results show that the transmission spectrum of the sensor exhibits the Fano resonance shape. The influences of refractive index and structural parameters on transmission characteristics are systematically investigated. The maximum sensitivity (S) of the sensor can get up to 2560 nm/RIU (refractive index unit), and the figure of merit (FOM) is 1080. In addition, the potential application of the structure in temperature sensing is explored with a sensitivity of 0.87 nm/degrees C. The proposed structure has promising applications in nanoscale optical sensing.