Design of a highly sensitive tunable plasmonic refractive index sensor based on a ring-shaped nano-resonator

In this paper, a high-sensitivity and tunable plasmonic refractive index sensor based on a nano ring- shaped resonator is proposed. This structure can be used as a multi-wavelength refractive index sensor with a maximum high-sensitivity of 2160 nm/RIU and maximum FoM of 55.2 RIU-1. The sensitivity is nearly 2 times higher than that of the previously reported basic structure based on a nanodisk shaped resonator. Besides, the sensitivity of the proposed structure is highest in comparison with the other reported works in recent years in this literature. The influences of various structural parameters on the transmission spectrum and sensing performance are comprehensively investigated using the finitedifference time-domain (FDTD) and finite-element (FEM) methods. More importantly, the results demonstrate that the sensitivity of the proposed sensor is robust to any fabrication fluctuation. Due to the simplicity of its topology and its easiness to be fabricated, the proposed high-sensitivity sensor can be a competitive candidate for sensing applications.