Metasurfaces for full control of reflected light

Abstract

Optical metasurfaces, being the two-dimensional analog of optical metamaterials, have in recent years gained considerable attention due to the possibility to control light on a subwavelength scale in unforeseen ways and the relative ease of fabrication, thus representing viable components for compact real-world applications. In this talk, we will discuss a certain type of plasmonic (i.e., metal-based) metasurfaces that allows for simultaneous control of the amplitude and phase of the reflected light for one polarization or, alternatively, to independently engineer the reflection phases for two orthogonal polarizations [1]. This almost full control of the reflected light is achieved through excitation of the fundamental gap surface plasmon (GSP) mode and, for this reason, this type of metasurface is also termed GSP-based metasurface. GSP-based metasurfaces consist of an optically thick metal film overlaid by a subwavelength thin glass spacer and a meticulously designed array of metal nanobricks (also known as nanopatches), hence enabling the possibility for realization by only one step of electron beam lithography. The great utility of GSP-based metasurfaces will be exemplified through various examples of inhomogeneous metasurfaces, ranging from plasmonic color printing [2], which corresponds to control of the reflection amplitude, to polarization-controlled unidirectional excitation of surface plasmon polaritons [3], which represents independent control of reflection phases for two orthogonal polarizations. Also, we demonstrate the possibility to simultaneously control the reflection amplitude and phase by performing calculus operations, like differentiation and integration, on linearly polarized incident light [4]. Finally, we utilize the new degrees of light control to design and realize compact polarimeters that allow for immediate determination of light's state of polarization [5]. The compactness, speed, and simple optical setup of the proposed polarimeters represent a first step towards real-life applications.