Interaction between optical nano-objects at metallo-dielectric interfaces

The light interactions between subwavelength apertures in metallic screens represent a basic diffraction phenomenon that has been studied for a long time. Initial reports have promoted the surface plasmon polariton (SPP) as the main vector responsible for the interaction. However, recent experimental results largely question this point of view and favour an interaction based on a new type of surface wave. Here we provide a comprehensive study of the different mechanisms involved in the electromagnetic interaction between optical nano-objects such as slits and holes at metallo-dielectric interfaces. We show that the interaction is driven by two very different near-field contributions, the SPP mode of the interface and a creeping wave. Although their relative impact strongly depends on the frequency range of interest and on the actual geometry of the nano-objects, SPPs are shown to be the primary vector of the interaction at visible frequencies.