Surface Plasmon Resonance Mode of Nanorods

This thesis discussed plasmon phenomena of various nano-structures, especially plasmonic modes, including a single gold nanorod, a single silver nanorod and gold nanorod-dimer structures, excited by electromagnetic plane wave and/or electrical dipoles. Maxwell theory together with the multiple-multipole (MMP) method is used to analyze the near-field surface plasmon resonance (SPR) and the far-field radiation patterns as well as the local field enhancement factor.
Results show that as the aspect ratio (AR) increases the corresponding wavelengths of plasmonic modes increase. For the case of normal incidence plane waves or symmetric bi-dipole, only odd modes are excited; while for the case of oblique incidence plane wave or asymmetry bi-dipole, both odd and even modes appeared. When dipole at the tip of nanorod, it can transfer energy to far end of nano-particle, in silver nanorods, the enhancement factors keep at 0.8.
For the case of gold nanorod dimer structures, for dimer with two identical nanorods, the bandwidth of dipole mode increases, while the peak of quadrupole mode weakens. For dimer with two different nanorods, if the wavelength of the quadrupole of long rod is close to that of the dipole mode of short rod, there is also a Fano resonance associated with a Fano dip due to a strong coupling between two nanorods.