A window-shaped resonator nanostructure based on an MIM waveguide for refractive index sensing

Optical sensors have many advantages such as anti-electromagnetic interference, fast response speed and low power consumption. However, the optical sensor cannot be further integrated due to the existence of diffraction limit. SPPs can overcome the diffraction limit and manipulate the optical signal in the subwavelength range, realizing the miniaturization of optical devices at the nanometer level. In this work, we presented an innovative sensor structure, which consists of a Window -Shaped Ring Resonator (WSRR) and a metal-insulator-metal (MIM) waveguide. The finite element method (FEM) was used to simulate the sensor characteristics. We analyzed the cause of Fano resonance, and optimized the performances of sensor by altering the parameters of the structure. The best sensitivity of the proposed structure is 1480 nm/RIU and the figure of merit (FOM) is 98.7. The presented refractive index sensor has promising applications in material sensing detection.