E-shaped and unsealed rectangular resonator assisted temperature sensor with high sensitivity.

A plasmonic temperature sensor based on a metal-insulator-metal (MIM) waveguide is proposed in this work. The sensor consists of an E-shaped resonator and an unsealed rectangular resonator on each side of the bus waveguide, which are filled with temperature-sensitive materials. The sensing performance of the sensor is investigated using COMSOL Multiphysics. We have systematically analyzed the influence of geometric parameters and materials of resonant cavities on the transmission characteristics and sensing performance. After optimizing the structural parameters as well as the plasmonic materials, the maximum sensitivity reaches 0.7 nm/°C when ethanol is used as the temperature-sensitive material, and the minimum temperature difference detectable within the range of 20.8°C-21°C is 0.01°C, and when temperature-sensitive material is modified to PDMS, the maximum sensitivity can increase to 0.8 nm/°C. The range for detecting the minimum temperature difference narrows to 20.4°C-20.6°C. We can flexibly select temperature-sensitive materials based on different detection environments without compromising sensing performance. Compared with similar MIM sensors, the proposed sensor supports multi-mode resonance and generates multiple resonant dips, thus providing rich sensing signals and improving measurement accuracy. It is especially easy to prepare and avoids errors caused by processing microstructures, such as stubs or baffles inside the bus waveguide. This provides development prospects for practical applications of high-sensitivity temperature measurement.