“Hot spots” induced near-field enhancements in Au nanoshell and?Au nanoshell dimer

The influence of “hot spots” on the near-field properties of Au nanoshell and Au nanoshell dimers have been investigated by means of the finite element method. It is found with increasing the pinhole radius R that the maximal enhancement of near-field for Au nanoshell with pinhole parallel to the polarization increases from 17.906 at R=0 nm to 36.979 at R=0.8 nm, and then almost shows a negligible radius dependence. Large electric fields also can be observed inside the pinhole perpendicular to the polarization, which increases with increasing the pinhole radius. The near-field of Au nanoshell dimer depends strongly on the polarization and propagation directions of the incident light. Exponential decay behavior is found for the maximal enhancement of the electric field in the dimer junction as a function of the dimer separation. Furthermore, a very strong electric field is found in the junction between two Au nanoshells when the pinholes are located near the gap between the nanoshells.