Mid-infrared sensing properties of a plasmonic metal–insulator–metal waveguide with a single stub including defects

A highly sensitive surface plasmon polariton-based sensor with a simple structure comprising a metal–insulator–metal waveguide with a single stub including several silver nanorod defects is designed and numerically investigated, using the finite element method, for application in refractive index sensors and temperature sensors. The simulation results show that the existence of silver nanorod defects in the single stub has a large influence on the sensitivity performance, which provides an additional degree by which to manipulate the system response at the nanometer scale. The refractive index sensitivity can reach as high as 5140 nm RIU –1 (RIU, refractive index unit) and the temperature sensitivity is about 2.05 nm °C −1 , which can be further improved by varying the length of stub, the radius of the defect rods and the number of defects in the stub. The sensing characteristics of the proposed simple structure could pave the way for highly integrated optical circuits for use in nanoscale refractive index sensors and temperature sensors with the single stub including the defects.