Surface plasmon enhancement for microsphere-assisted super-resolution imaging of metallodielectric nanostructures

Abstract

Using a two-dimensional hexagonally close-packed SiO2/Ag nanoshell array coated with or without a dielectric layer as an imaging object, we find that the imaging quality of microsphere-assisted microscopy depends strongly on the optical properties of the metallodielectric sample. When a thin dielectric film is deposited on the top surface of a SiO2/Ag nanoshell array, a periodic enhanced near-field electric field is formed at the interface between the Ag layer and the deposited dielectric layer due to the excitation of surface plasmon polaritons. By increasing the dielectric constant of the coating layer, the enhanced near-field electric field region becomes larger and extends into the region which is closer to the imaging system. When the SiO2/Ag nanoshell array is coated with a SiO layer, the best resolution, the highest magnification, and the longest working distance are obtained. And, a SiO coated nanoshell array with a core size of 180 nm (λ/3, where λ = 540 nm is the central wavelength of illumination) can be resolved.