Enhance the detection of surface micro/nanostructures by SPPs generated from silver film covered hemi-microsphere

Surface plasmon polaritons (SPPs) are widely used for surface micro/nanostructures detection. However, because of the limitations of the common SPPs excitation conditions, it is difficult to flexibly detect surface micro/nanostructures in the air without being limited by the substrate structure. In this paper, a new SPPs excitation structure is developed. This structure is a silver film covered hemi-microsphere. SPPs could be excited on the surface of the Ag film, and induce collective oscillations of free electrons on the substrate surface to generate periodic electromagnetic waves. The periodic electromagnetic waves can enhance the electromagnetic field around the surface micro/nanostructures, which could benefit the detection of those surface micro/nanostructures. This method could work in the air, and requires less of the sample structure, but also could move above the sample to achieve a large range of detection. Simulation experiment results demonstrate that this structure has a good detection effect. The maximum enhancement achieved for nanoparticles is 113-fold. This structure holds great potential for medical detection and biosensing.