Optical antennas: Resonators for local field enhancement

TLDR

The study investigates electromagnetic field enhancement in optical antenna arrays at midinfrared wavelengths using simulation and experiment. Optical antennas are designed to confine intense optical fields to subwavelength dimensions at resonance, fabricated on transparent substrates by electron beam lithography, and characterized via finite‑difference time‑domain simulations of current, charge, and field distributions. The results show that antenna shape, length, and sharpness influence field intensity, the resonant wavelength depends on length and material, and calculated extinction efficiencies agree well with experimental measurements.

Abstract

Electromagnetic field enhancement in optical antenna arrays is studied by simulation and experiment at midinfrared wavelengths. The optical antennas are designed to produce intense optical fields confined to subwavelength spatial dimensions when illuminated at the resonant wavelength. Finite difference time domain (FDTD) method simulations are made of the current, charge, and field distributions in the antennas. The influence of antenna shape, length, and sharpness upon the intensity of the optical fields produced is found. Optical antennas arrays are fabricated on transparent substrates by electron beam lithography. Far-field extinction spectroscopy carried out on the antenna arrays shows the dependence of the resonant wavelength on the antenna length and material. The FDTD calculated and experimentally measured extinction efficiencies of the optical antennas are found to be in good agreement.