Strong and tunable plasmonic field coupling and enhancement generating from the protruded metal nanorods and dielectric cores

Numerical investigation of resonant peak by modifying the number of protruded metal nanorods (MNRDs) and the core material in metal nanoshells for near field intensity are explored by means of the finite element method. The surface plasmon effect arising from the core cases with/without the protruded MNRDs was compared along with that arose from their solid counterparts. A strong and tunable field coupling and enhancement effects corresponding to the transverse surface plasmon resonance (SPR) and cavity plasmon resonance (CPR) modes are observed. It is found that the near field intensity spectra obtained from the silver and silver-shell nanorods with the protruded silver nanorods is approximately 2.5-3.0 times larger than that of the silver nanorods without the protruded silver nanorods. The peak resonance wavelength shows a red shift as the increasing of the permittivity in the core regions and the number of the protruded MNRDs. This indicates that the core regions and the protruded MNRDs can significantly mediate the EM waves coupling and enhancing the plasmonic effects and play a key role to tune the peak resonance wavelengths position. The investigated nanostructures offer multiple design freedoms to modulate the peak resonant wavelength and electromagnetic wave properties.