UC San Diego

Planar structured interfaces, also known as metasurfaces are continuously attracting interest owing to their ability to manipulate fundamental attributes of light including angular momentum, phase polarization. Metasurface can utilize abnormal phase abrupt changes at an interface to manipulate electromagnetic wave fronts. It provides an effective method for applications including planar lens imaging, polarization splitter, half-wave plate, extra thin layer hologram and so on. Different from traditional optical devices are bulky, metasurfaces are thin layers with multifunction, low loss, and easy to integrate. Due to their advantages, metasurfaces have become a rapidly growing field of research and have attracted wide attention. In this dissertation, we focus on both physics and applications of manipulating electromagnetic (EM) wave fronts with the metasurfaces. First, we review the mechanics of metasurface and the general design methods of metasurfaces. Secondly, as the application, we demonstrate a novel and simple approach to cloaking a scatterer on a ground plane with an extremely thin dielectric metasurface. The metasurface compensates the wave fronts distortion by a scatterer. With this design, any observer will just see a flat ground plane and the scatterer will be invisible and thus effectively cloaked. Then, a linear polarization broadband metasurface carpet cloaking at visible is studied. We reveal the requirements of linear polarization broadband (wavelengths from 650 nm to 800 nm) metasurface carpet cloaking and propose a unit cell to provide the required phase. The 2D simulation results show the distortion is fixed due to our metasurface design and the 1D result further show the quantity of corrected phase. In additional to linear polarization broadband metasurface carpet cloaking, we also investigate linear polarization, high efficiency, and broadband achromatic meta-lens. Despite exciting findings, achieving simultaneously high efficiencies and large bandwidths has remained a challenge. Recent state of the art results in the visible reported a bandwidth from 470 nm to 670 nm with an efficiency of 20 % while the efficiency of 40% was obtained for the bandwidth from 400 nm to 660 nm. Here, we experimentally report polarization-independent, fishnet-achromatic-metalenses (FAM) with measured average efficiencies over 70% in the band from the visible (640 nm) to the infrared (1200 nm).

Metasurfaces are so far demonstrated using unit cell method where the approach usually used to engineer metasurface devices assumes that neighboring elements are identical, by extracting the phase information from simulations with periodic boundaries, or that near-field coupling between particles is negligible, by extracting the phase from single particle simulations. In this thesis, we proposed a new method that quantify the phase error of each element of the metasurfaces with the proposed local phase method paves the way to the design of highly efficient metasurface devices including, but not limited to, deflectors, high numerical aperture metasurface concentrators, lenses, cloaks, and modulators. As illustrations, we proposed to use deflectors and high numerical aperture concentrators where we demonstrate an improvement of 100% compare to unit cell method. We also introduced and evaluated the intercept factor and the slope error from solar industry to quantify fabrication imperfections. The concept opens a new path to calculate metasurfaces sensitivities to fabrication imperfections and will be critical for practical systems. The concept paves a new way to calculate metasurfaces sensitivities to fabrication imperfections and will be critical for practical systems.