Ellipsoid Defect in Trapezoidal-Shaped Cavities Coupled to Multi-resonance Plasmonic Metal–Insulator-Metal Waveguide Toward Ultrasensitive Temperature Sensor

A multi-resonance plasmonic temperature and refractive index (RI) sensor is developed based on a metal–insulator-metal (MIM) waveguide with two trapezoidal-shaped cavities and an elliptical island inside. Different dielectrics including ethanol, chloroform, carbon disulfide, glycerin, and polydimethylsiloxane (PDMS) have been utilized for the temperature investigation in the range of − 50 to 70 °C. Results revealed the maximum temperature sensitivity (TS) of 1.058 nm/°C and the maximum temperature figure of merit (FoM) (FoM T ) of 0.0141 1/°C which correspond to the carbon disulfide and PDMS in the first resonance (FR), respectively. The RI-sensitivity (RIS) of this sensor at the first and second resonance (SR) is 1328.57 nm per RI unit (RIU) and 735.71 nm/RIU as well as its FoM which is 36 1/RIU and 31.31 1/RIU, respectively. This paper confirms the high capabilities for measuring the temperature and RI in a wide spectral range of wavelengths (600 to 3000 nm), and multi-resonance sensing. This reveals significant potential in optical and photonic circuit applications such as different quantities detection, including hemoglobin and cancer.