Optical Properties of UT-Shaped Plasmonic Nanoaperture Antennas

In this paper, we present numerical and experimental results on optical properties of a multi-resonant UT-shaped plasmonic nanoaperture antenna for enhanced optical transmission and near-field resolution. We propose different structure designs in order to prove the effect of geometry on resonance spectrum and near-field enhancement. Theoretical calculations of transmission spectra and field distributions of UT-shaped nano-apertures are performed by using three-dimensional finite-difference time-domain method. The results of these numerical calculations show that transmission through the apertures is indeed concentrated in the gap region. In addition to theoretical calculations, we also performed a lift-off free plasmonic device fabrication technique based on positive resist electron beam lithography (EBL) and reactive ion etching in order to fabricate UT-shaped nanostructures. For further confirmation of the multi-resonant behavior, we checked the individual U- and T-shaped nano-aperture antenna responses. We also studied the parameter dependence of the structure to determine the control mechanism of the spectral response. Theoretical calculations are supported with experimental results to prove the enhanced field distribution and multi-resonant behavior which can be suitable for infrared detection of biomolecules, wavelength-tunable filters, optical modulators, and ultrafast switching devices