Plasmon tuning and electromagnetic field enhancement of Au@Ag nanorod-gold film nanostructure

In this paper, the finite element method is used to calculate the extinction optical properties and electric field distribution of gold core silver shell nanorod-gold film nanostructures. The volume ratio of silver and the length diameter ratio of core-shell nanorods can be changed by controlling the thickness of silver layer, which can realize the regulation of the longitudinal mode peak position from 600 to 900 nm. The electric field intensity of the core-shell nanorod-gold film structure increases with the increase of the volume ratio of silver. Silver is the plasmon material with the smallest loss in the visible light region, due to its small imaginary part of the dielectric function and lower plasma damping than gold. Therefore, with the increase of the volume ratio of silver, the extinction spectrum intensity of the gold core silver shell nanorod-gold film increases obviously, and the blue shift of the peak position and the narrowing of the full width at half maximum of the wave shape are obvious changes. At the same time, the structure gap confines the light to the deep sub wavelength range, which will produce a hot spot in the gap, which will enhance the electric field.