Resonantly Enhanced Absorption in Bifurcation Plasmon Nanostructures for Refractive Index Sensing

By changing or fine-tuning the surface structure of the metal, the characteristics of surface plasmon-especially the interaction with light-can be customized. In this work, we numerically design a plasmonic nanostructure composed of a pair of symmetrical bifurcation nanostructures. The composite nanostructure has significantly enhanced optical absorption, and a sharp groove is generated in the scattering spectrum due to the plasmon mode hybridization. The extremely intense and highly confined electromagnetic fields induced in the bifurcation plasmon nanostructures provide a sensitive environment to probe minor changes in the dielectric environment, and the simulation result shows that the average sensitivity is about 699 nm/RIU with the refractive indices from 1.332 to 1.467. Such high-performance composite nanostructure provides great potential for the application of SERS probing and label-free biosensing.