Discrete Dipole Approximation Simulation of the Surface Plasmon Resonance of Core/Shell Nanostructure and the Study of Resonance Cavity Effect

Nanoshells have been previously shown to tune absorption frequencies efficiently. What will happen when a nanoshell embeds on a small core system? A theoretical model that a core composed of gold is embedded within a nanoshell of Au/Ag is constructed to answer this question. The calculations based on the discrete dipole approximation (DDA) method are performed and proved to converge accurately by satisfying the usual criteria related to the applicability of the DDA. The results show that the nanoshells in the core/shell system greatly influence the surface plasmon resonance (SPR). Indeed, the shell frequency is tuned to match the optical properties of the absorbing core leading to hybridization/mixing and possibly overall enhancement of absorption cross-section. The calculation of the field enhancement also shows that the location of the field enhancement is specified by the different resonance patterns.