Nanostructured Optical Materials for Planar Photonics

Abstract

How a material interacts with light, whether it is reflective, transparent or absorptive, results form the fundamental properties of the atoms and molecules comprising the material. Adding a suitably-designed geometry to the material allows one to manipulate the light that is interacting with the material---adding curvature to glass allows one to focus light down to a point. However, the set of available responses from naturally-occurring materials is still limited. 'Metamaterials' are materials that have been artificially structured on dimensions smaller than the wavelength of light, allowing one to achieve a set of optical responses beyond traditional materials. Metamaterials, however, are incompatible with fabrication processes standardized by the electronic industry (semiconductor processing) and often have unusably-high losses. This thesis details the use of metasurfaces, the two-dimensional analog of metamaterials, which can be processed using standard production techniques while replicating or expanding on many of the functionalities of conventional optics and metamaterials. A particular emphasis is placed on the realization of metasurfaces at visible wavelengths, where material processing and fabrication challenges are amplified due to the smallness of the wavelength. It is shown that the combination of materials engineering, nanofabrication and device design enable new fundamental physical phenomena---controllable coupling between spin and orbital angular momentum in light---as well as substantial increases in the efficiency of metasurfaces---planar lenses and holograms with orders of magnitude reduction in thickness.