Shedding light on fractals : exploration of the Sierpinski carpet optical antenna

Abstract

We describe experimental and theoretical investigations of the properties of a fractal optical antenna-the Sierpinski carpet optical antenna. Fractal optical antennas are inspired by fractal antennas designed in radio frequency (RF) region. Shrinking the size of fractal optical antennas from fractal antennas in RF regions by a factor of lE-5 arises challenges of fabrication, characterization and modelling their response to incident light. The comparison between optical antennas with the Sierpinski carpet geometry and other geometries is also an interesting topic. Generally speaking, this thesis covers the fabrication, the theoretical investigations of the properties of eigenmodes and the characterization of Sierpinski carpet optical antennas by optical techniques. The broadband response and hot-spot distribution of a Sierpinski carpet optical antenna have been investigated by the white-light dark field and two-photon photoluminescence microscopy respectively, and results are compared with two other morphologies: the pseudo-random and periodic nanostructures. The subradiant surface lattice resonance of a Sierpinski carpet optical antenna has been investigated by the back focal plane microscopy. Due to the versatile application of optical antennas, the generalization and application of the theoretical and experimental techniques to other plasmonic arrays, or even the application of the Sierpinski carpet optical antenna itself to other areas of light­ matter interaction, can be expected.