Graded metareflectors for wave manipulation and control at the nanoscale

Optical metasurfaces, or planarized metamaterials, are based on engineered subwavelength inclusions intentionally designed to provide desired advanced functionalities, unavailable with conventional gratings, by exploiting their anomalous localized response. Metasurfaces have been investigated both theoretically and experimentally in various recent studies, but most of the available examples are limited to strictly periodic structures. In this work we introduce a novel planarized metasurface reflector composed of deeply subwavelength nonperiodic inclusions arranged to impart the desired arbitrary phase distribution at the nanoscale. We obtain exciting and unique wave interaction properties, and we outline their potential applications at optical frequencies, demonstrating a novel photon management approach for broadband light absorption enhancement in thin-film solar cells, an efficient, low-dispersion integrated on-chip coupler, and a new concept for ultrathin optical carpet cloaks.