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.