A dual-purpose sensor with a sawtooth U-shaped cavity and a rectangle-shaped cavity in a MIM waveguide structure

Abstract To improve the performance of subwavelength refractive index and temperature sensors, this paper proposes a subwavelength metal-insulator-metal (MIM) waveguide structure consisting of a sawtooth U-shaped cavity and a rectangular cavity based on surface plasmon polaritons. The transmission spectrum of the system is simulated using the finite element method (FEM) and verified with multi-mode interference coupled-mode theory (MICMT). The results demonstrate excellent sensing characteristics for the system, with a refractive index sensitivity of 1300 nm RIU −1 , a figure of merit (FOM*) of 191.262, and a temperature sensitivity of 0.525 nm/°C. This indicates that the nano-plasma system is highly significant in refractive index and temperature sensing.