Field Enhancement by a Metallic Sphere on Dielectric Substrates

We calculate the scattered local field around a small gold sphere on dielectric substrates which is illuminated by a collimated monochromatic beam. The numerical results show the field between the sphere and the substrate is much enhanced when the sphere is illuminated by a p-polarized beam. The enhanced area is very localized between the sphere and the substrate and the diameter of the enhanced area on the surface of the substrate is one fifth of the sphere diameter. The field increases as the gap distance decreases or as the refractive index of the substrate increases.This paper was originally presented at the 5th International Conference on NEAR FIELD OPTICS and RELATED TECHNOLOGIES (NFO-5), which was held on December 6–10, 1998 at Coganoi Bay Hotel, Shirahama, Japan, in cooperation with the Japan Society of Applied Physics and Mombusho Grant-in Aid for Scientific Research on Priority Area “Near-field Nano-optics” Project, sponsored by Japan Society for Promotion of Science.