Plasmonic sensors based on Metal-insulator-metal waveguides for refractive index sensing applications: A brief review

Optical sensors are widely used for refractive index measurement in biomedical, chemical, and food processing industries and offer high sensitivity to ambient refractive index variations due to the specific field distribution of the resonances. The sensor's sensitivity is greatly dependent on its material and structure. In this review, we focused on plasmonic refractive index sensors with no fluorescent labelling required. The latest developments on special types of plasmonic structures such as metal-insulator-metal waveguides and their application in refractive index sensors are presented. Moreover, numerous types of plasmonic waveguides, geometries, materials, fabrication processes, and losses related to plasmonic waveguides are explained to provide a better understanding of this topic. The highlight of this review is to discuss the spectral performance of recently reported refractive index sensors by emphasising their sensitivity and figure of merits.