Cog-shaped refractive index sensor embedded with gold nanorods for temperature sensing of multiple analytes.

This article presents a refractive index (RI) nanosensor utilizing gold as the plasmonic material. The layout of the sensor includes metal-insulator-metal (MIM) waveguides coupled with a cog-shaped resonator studded with gold nanorods. At the mid-infrared (MIR) spectrum, the spectral characteristics of the sensor are numerically analyzed employing the finite element method (FEM). Moreover, the refractive index sensing property is thoroughly explored by varying the key parameters, establishing a linear correlation with the transmittance profile. After extensive simulations, the most optimum structure displays the highest sensitivity of 6227.6 nm/RIU. Furthermore, the capability of the proposed device as a temperature sensor is investigated with five different liquids (ethanol, polydimethylsiloxane, toluene, chloroform, and the mixture of toluene and chloroform); among these, chloroform exhibits maximum temperature sensitivity of 6.66 nm/°C. Due to being chemically stable and demonstrating satisfactory performance in RI and temperature sensing, the suggested schematic can be a suitable replacement for silver-based sensors.