Spatial Confinement of Light onto a Flat Metallic Surface using Hybridization between Two Cavities

Controlling the optical field down to the nanometer scale is a key step in optoelectronic applications and light matter interaction at the nanoscale. Bowtie structures, rods and sharp tapers are commonly used to realize such optical properties, but their fabrication is challenging. In this context, the complementary structures, namely holes and cavities, are less explored. Herein a simple system of two metallic nano-cavities milled in thin silver film is used to confine the electromagnetic (EM) field to an area of ~60nm. The field is confined onto a flat surface area and is either enhanced or suppressed by the polarization state of incident light. The energy of this spatially confined mode is determined by the distance between the two cavities and thus any color (wavelength) at the optical regime can be achieved. As a consequence, a dynamically controlled wavlength is generated on a pixel size smaller than one micron square. If molecules are deposited onto those ‘hot spots’, they should experience a very strong EM field that may shape their potential energies and thus open a new pathway for controlling photochemical processes on surfaces. Those results are supported both by transmission spectra and a Cathodoluminescence study.