Enhanced Temperature and Refractive Index Sensor Based on InSb Plasmonic Waveguide Resonator Structure with a Disk Defect

In this study, a Fano resonance system based on a semiconductor-insulator-semiconductor (SIS) plasmonic waveguide with integrated resonators is proposed for the first time. The device shows high sensitivity with a multi-mode plasmonic resonator and an InSb defect. The sensor uses InSb as the plasmonic material which offers numerous advantages over conventional noble plasmonic materials. The sensor takes advantage of the tunable optical properties of the InSb to detect changes in the external environment temperature and refractive index which has been demonstrated using the finite difference time domain (FDTD) method. The double Fano resonance line and field patterns of the structure are numerically simulated. It is found the double Fano resonances are originated from the coupling between the continuous spectrum supported by the stub and discrete localized states provided by the square cavity. Additionally, the profile of the double Fano spectrum can be tuned by adjusting the geometrical parameters. Besides, owing to the permittivity-dependent nature of InSb, the Fano resonance dip can be manipulated by adjusting of ambient temperature. The strong dispersion of the Fano peak will lead to slow light; therefore, active control of slow light can be achieved by changing the ambient temperature. Based on the proposed structure, an InSb disk defect is added to the square cavity, triple Fano resonance spectra can be observed. The field enhancement effect caused by the defects results in a greater sensing sensitivity. These characteristics offer flexibility and tunability in the design of the highly efficient plasmonic sensor for both refractive index and temperature sensing. The improved structure yields a sensitivity of 8.96x10(-4) THz/k and 0.76 THz/RIU. The optimal figure of merit (FOM) and maximum Q factor of the Fano dip are about 149.1 and 160.7, respectively. This multi-parameter high-sensitivity plasmonic sensor may find important applications in THz-slow light, sensors, and modulators.