Novel optical antennas inspired by metamaterial architectures

Abstract

The spatial resolution of conventional optical systems is commonly constrained by the diffraction limit. This is a fundamental problem important for various high-tech applications including density limitation in data storage devices (CD, DVD, and Blue-ray discs), crosstalk in detectors, and blurred images in microscopy. To overcome this limit, different types of optical antennas have been investigated to date. However, these antennas either do not exhibit a maximum level of field intensity enhancement that can be achieved via field localization using plasmons or they have large field intensity enhancement at the cost of complicated three-dimensional architectures or very sharp tips, which are hard to fabricate. In this thesis, to address this problem, we investigate a new class of planar optical antennas inspired by metamaterial architectures including E-shape and comb shape. We found that the field intensity enhancements inside the gap regions of such comb-shaped nanoantennas were significantly increased compared to the single or array of dipoles, despite operating across an electrical length significantly reduced with respect to their resonance wavelength. We also showed that the field intensity localization of a single dipole nanoantenna can be at least doubled using single ring resonator with the same gap size by decreasing field radiations from end points and obtaining continuous current flow. These results indicate that comb-shaped planar nanoantennas hold great promise for strong field localization.