|approved||wave_manipulation_using_metasurfaces_one_page_final_larger2.pdf||2015-04-14 14:47:39||Nasim Mohammadi Estakhri|
Author: Nasim Mohammadi Estakhri
Requested Type: Oral
Submitted: 2015-04-06 09:42:18
The University of Texas at Austin
1616 Guadalupe St., UTA 6.426
Austin, Texas 78701
One of the most intriguing prospects of optical metasurfaces is their ability to manipulate at will the spatial distribution of electromagnetic waves, transforming arbitrary incident wave profiles into the desired scattered beam. Following the proposal of plasmonic metasurfaces to create abrupt and spatially inhomogeneous phase discontinuities, several proof-of-concept designs have been theoretically and experimentally put forward, realizing functionalities such as anomalous reflection and refraction, focusing, generation of twisted light, and retardation. Wave engineering using metasurfaces has so far been exclusively based on passive structures whose local properties are engineered to provide the desired local phase discontinuity, essentially based on a ray-optics approach. In our presentation, we demonstrate that this approach neglects the influence of impedance matching, and the coupling efficiency into the desired outgoing wave is fundamentally limited. We also discuss that in principle, active surface components are required to realize 100% conversion efficiency, and these constraints become more stringent for extreme operations such as large-angle beam bending or focusing in the very near-field. Based on rigorous solution for the wave interaction with gradient metasurfaces, we present a novel technique to design passive metasurfaces with enhanced efficiencies and discuss their performance for several applications, including beam steering, focusing and cloaking.