Development of a Plasmonic Refractive Index Sensor with Enhanced Sensitivity

Abstract

Plasmonic devices are based on the propagation of surface plasmon polaritons. In this thesis, waveguide design with metal-insulator-metal configuration is considered to support the propagation of the surface plasmon polaritons. Silver has been placed as metal. The design topology of the refractive index sensor, as well as its design parameters, are the fundamental parameters to improve the performance of the sensor. The plasmonic refractive index sensors with a straight waveguide and different side coupled resonators have been proposed and analyzed. The equilateral triangular, regular pentagonal, and semi-circular resonator are the three different designs of the resonator. The resonators are of disc-type and ring-type. The finite element method has been implemented as a numerical computational tool. The scattering boundary condition is implemented on the non-port boundary of the sensors. The detection of refractive index change has been numerically simulated and analyzed using COMSOL Multiphysics. The simulation environment has been validated by re-simulating an existing sensor from the literature. The re-simulation results have been compared and found a maximum error of 4.14% in sensitivity calculation. The sensitivity achieved using our proposed designs has been found to be 2713 nm/RIU with a high figure of merit (FOM) of 35.1 for the design with the ring-type triangular resonator. It is shown that the sensor can detect a refractive index change of 3:68 10����6, which is the sensing resolution of the sensor, for dielectrics whose refractive indices are between 1 to 1.03 and also between 1.33 to 1.42. This range of refractive index indicates the application of the sensor as a gas sensor and biosensor. Simplicity and compact design with high refractive index sensitivity and FOM of the plasmonic device make the design comparable with many excellent sensors in the literature. The other significant applications of the sensor cover bio-sensing, biomedical applications like cancer cell detection, nanosensing, and optical filter applications.