Design and Optimization of Dielectric Metasurface Optics

Thesis (Ph.D.)--University of Washington, 2019In recent years, sub-wavelength, aperiodic gratings, currently coined metasurfaces have the potential to manipulate electromagnetic elds with extreme control in a remarkably small form factor. These planar optical components promise to manipulate incident elds at the wavelength scale to achieve unprecedented functionalities. This extraordinary exibility arises from the extremely large numbers of tunable degrees of freedom characterizing the individual discrete scatterers. This thesis details two methods for the design of these optical elements, a forward method, and an inverse method. First, a forward design method is described for metasurfaces based on a silicon nitride nanopost platform. Results from experiments characterizing metasurface lenses, vortex beam generators, cubic phase plates, and Alvarez lenses are presented. These optical elements were all designed to operate in the visible frequencies, and fabricated using conventional top-down semiconductor lithography. Then, a general inverse design method is described for discrete spherical scatterer based optical elements. Simulation results for single layer and multilayer lenses for fabrication using a 3D printer are shown, and simulation and experimental results for a novel optical element producing a discrete helical focusing pattern is presented