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 10². The uniqueness of this new design lies in the ability to fabricate them with high accuracy in gap size control.