Design of a High-Resolution Metal-Insulator-Metal Plasmonic Refractive Index Sensor Based on a Ring-Shaped Si Resonator

In this paper, a high-resolution refractive index sensor is proposed based on a novel metal-insulator-metal plasmonic topology. The structure is based on a Si nano-ring located inside a circular cavity. It acts as an optical notch filter with a quality factor equal to 269. The proposed filter topology is numerically simulated using the finite difference time domain method. It is shown that the proposed filter can also act as a refractive index sensor with a sensitivity of 636 nm/RIU and a fairly high figure of merit (FoM) equal to 211.3 RIU-1. It is shown that the sensor can easily detect a refractive index change of +/- 0.001 for dielectrics whose refractive index is between 1 and 1.2. For the refractive index range of 1.33 to 1.52, the maximum FoM of the sensor is 191 RIU-1. The simplicity of the design and its high resolution are the two main features of the proposed sensor which make it a good candidate for biomedical applications.