Enhanced Refractive Index Sensing in an Ag-Dielectric-Ag Plasmonic Waveguide via an Embedded WS2 Layer

We design and analyze a plasmonic metal dielectric metal waveguide sensorbased on a novel configuration, where a WS2 nanolayer is employed insidethe dielectric core rather than at the conventional metal dielectric boundary.In our configuration, the propagating surface plasmon polaritons interact directly with the WS2 layer inside the sensing region. We study the effect of theWS2 position and thickness on the transmission spectra and refractive indexsensitivity using the finite element method. We compare our design witha conventional MDM waveguide and with a conventional configuration inwhich the WS2 layer is placed at the metal dielectric boundary. Our resultsshow that embedding the WS2 nanolayer inside the dielectric core strengthens the light-matter interaction, improves field confinement, and enhancesthe refractive index sensitivity. Within the refractive index range of 1.33 to1.4, we find that a 5 nm WS2 layer provides the highest sensitivity of 571nm/RIU. We also employ a graphene layer at the metal dielectric boundarytogether with the embedded WS2 layer to evaluate a hybrid configuration.However, the graphene layer does not provide any additional improvementin sensitivity. The proposed configuration offers an effective approach fordeveloping compact plasmonic waveguide sensors for on-chip refractive indexsensing applications.