Optical Characteristics of Rhombic Hybrid Au-Ag Nanostructures Calculated by Discrete Dipole Approximation Method

The extinction spectra of rhombic hybrid Au-Ag nanostructures have been calculated using the discrete dipole approximation (DDA) aided design method. The plasmon peaks of the rhombic hybrid Au-Ag nanostructures can be tuned not only by the structural parameters but also by the effective refractive index of the medium surrounding around the nanostructures. The relationship between the extinction efficiency and the polarizations of the incident light are also analyzed by the DDA method. Based on the calculated curves, the main parameters of the nanostructure arrays such as thickness, period and the refractive index sensitivity can be determined. Using this aided method, a hybrid Au-Ag nanostructures array is designed with the determinant parameters of thickness (Au 5 nm, Ag 25 nm), period (400 nm) and the refractive index sensitivity (400 nm/RIU). This study shows that the particle material, period and the effective refractive indexes of the mediums have significant effect on the optical properties of the nanostructures, and DDA aided design method can provide the perfect structure parameters for our hybrid nanostructures.