Numerical Studies of Metal-Dielectric-Metal Nanoantennas

We propose a new design of optical nanoantennas and present numerical studies of their optical properties. The nanoantennas are composed of two metallic parts stacked vertically with a dielectric spacer. The calculated near-field and far-field spectra show cavity resonances, which produce sharp peaks in local field spectra and leave their fingerprints as multiple dips in the far-field scattering spectra. Numerical results also show that the local field enhancements inside the cavity can be tuned by varying the size of the dielectric spacer and that a gap of 5 nm or less promises an extraordinary electromagnetic field enhancement on the order of 10(2). The uniqueness of this new design lies in the ability to fabricate them with high accuracy in gap size control.