Frequency-selective absorption characteristics of a metal surface with embedded dielectric microspheres

The coupling of the resonances of spherical particles embedded near the surface of a metal and the surface plasmon is investigated by calculations using a multiple scattering formalism. The system we considered is a periodic array of glass spheres buried just beneath the surface of an Ag substrate. The calculated absorption spectra show features that can be traced to the resonance frequency of the microsphere cavity or the surface mode of the metal. In general, the absorption peaks for both the cavity and the surface mode are relatively weak when their resonance frequencies are far from each other. However, if the system is designed such that the cavitylike mode and the surface mode have almost the same frequency, the coupling of the resonances will lead to enhanced frequency-selective absorption. Such systems can be employed to modify or control thermal emission.