MIM based plasmonic Refractive Index (RI) sensor, Demultiplexer and Filter with Resonant Cavities.

Abstract

Three high-yielding plasmonic refractive index (RI) structures are proposed in this the- sis. Those are sensor, demultiplexer and filter. To meet contemporary sensing demands in various industries, such as medical, forensic, and industrial, a sensor consisting of a U-shaped cavity connected with a sub-annular circle was developed. An ultra modern plasmonic 1x2 demultiplexer was made to meet the lackings of conventional demulti- plexers such as reduction of bandwidth wastage and minimization of signal delay. The final proposed model of this thesis is a triple ring resonator filter. The optimized filter shows promising results with the minimum possible transmittance. All three struc- tures were constructed using gold as the metal base to ensure minimum oxidation. The wave-solver is COMSOL Multiphysics, which uses the Finite Element Method (FEM) by default. The computational precision of COMSOL Multiphysics is demonstrated through re-simulations of existing structures. Furthermore, the refractive index and the resonant wavelength are linearly related in all three proposed sensors created using the nanoimprint lithography technology. To perceive unknown materials, this linear relationship is used. Furthermore, plasmonic structures’ structural properties are sus- ceptible to changes. As a result, the proposed structures are subjected to intensive simulations and optimization processes in order to improve their performance. The proposed sensor was a plasmonic refractive index sensor that had an initial sensitivity of 1320 nm/RIU. After proper optimization, a maximum sensitivity of 3120 nm/RIU was obtained. The proposed second work with triple ring resonators with rectangular stubs had an initial transmittance dip of 0.062 is observed at the wavelength of 974.7 nm. This re- sult was optimized by adding and varying various structural parameters. The optimized transmission dip obtained is 0.0023 at the wavelength of 912.5 nm which is very low and thus most of the energy is blocked or filtered. The final structure is a 1×2 channel demultiplexer with concentric ring and nanodisk directly coupled with MIM waveguide. Despite using gold, high quality factor of 22 and 25 were achieved for port 1 and port 2 respectively after intensive optimization. Besides channel spacing of 124 nm was also found. The proposed structures within the book have satisfactory results and is suitable for practical purposes.