Design and analysis of a very highly sensitive plasmonic refractive index sensor for sensing material measurement

A highly sensitive sensor based on metal–insulator-metal nanostructure with new branches is proposed. The performance of this sensor is based on measuring the refractive index of the sensing materials. This measurement is used to diagnose medical conditions such as cancer, diabetes, and blood infections by detecting small changes in the refractive index of biological samples. The performance of the proposed structures is evaluated by two methods finite-difference-time- domain (FDTD) and transmission line model (TLM). By adjusting the geometry and number of the branches (from 1 to 6), the sensitivity of the structure reaches its maximum value of 2620 nm/RIU. Also, the presence of more modes in a wide range of wavelengths from 800 to 3000 nm leads to the adjustability of this structure. Optimizing the dimensions significantly enhances sensitivity, achieving values far beyond those of previously reported plasmonic sensors. The bandgap width can be adjusted with optimal design and the maximum value of 900 nm can be achieved which has a 3800% increase with the increase in the number of branches. As a result, this high-sensitivity sensor can be a therapeutic candidate that is used to produce very complex integrated circuits.