Gap plasmonic properties of NPOM structures composed of gold nanoparticles and thin films

Metal nanoparticles have attracted great interest because of their unique near-field enhancement properties, and have important applications in many fields, such as surface-enhanced Raman scattering (SERS), fluorescence enhancement, solar cell efficiency enhancement and so on. In this paper, we use the finite element method to study the local field enhancement characteristics of the coupling system in which the gold ellipsoidal nanoparticles (GENP) on a mirror. In the coupling system, a hot spot will be formed at the gap between the GENP and the mirror under the appropriate incident light excitation. Based on the structural characteristics of GENP, we systematically study the local electric field produced by placing ellipsoids vertically and horizontally on the mirror. Under the excitation of the same polarized incident light, the maximum local electric field of the vertical GENP is 2200 (V/m), while that of the horizontal GENP is more than 9400 (V/m). Our proposed gap coupling system based on metal nanoparticles and thin films may open a new field of interest in the fields of plasmon, sensing, optical limitation and enhancement.