Optical nanoantenna optimization for local field enhancement at visible wavelengths

Abstract

Dipole nanoantennas are studied by means of numerical calculations, over a broad frequency range (250-600 THz), in order to evaluate the benefits of its integration in NSOM microscopy systems. Operational wavelength, radius and material were systematically varied to study the antenna’s resonant length, the field confinement, enhancement and decay. To perform more accurate calculations we implemented an algorithm to include real metal dispersion, at optical wavelengths, in the simulation. The simulations’ results suggest that the antenna’s performance depends strongly on the material’s dielectric properties; even aspects that we would relate only with the antenna geometry like field confinement. By comparing gold and aluminum antennas we found a crossover wavelength for the antenna performance. Below this wavelength aluminum is a more suitable material while for larger wavelengths gold gives better results.