Planar photonic metasurfaces, exhibiting artificial optical effects at the interface, are enabling a broad variety of possibilities as optical elements, communications, and signal processing. The signal we perceive from a metasurface is determined by the phases of the different nanostructures that compose the system. This phase controls the spatial radiation distribution following Huygens’principle and has been utilized in planar optical devices exhibiting negative refraction, cloaking, and holographic elements to name a few.
In this presentation, we will first demonstrate the quantitative direct measurement of the phase front produced by a metasurface using digital holography microscopy. We will then show that by designing and tuning the multipolar components of the nanostructured building blocks, it is possible to also control the spectral response as well as the polarization state of the system. By composing a metasurface with such complex nanostructures fabricated in silver, we are able to control the scattered light and channel different colors into different directions. In the second series of experiments, we specifically study the multipolar radiation of a bianisotropic scatterer and use it for the efficient splitting of circularly polarized light, similar to a photonic spin Hall effect. Since the near-field enhancement and circularly polarized scattering in this case occur at the individual antenna level, this planar surface is capable of extracting the fluorescence and controlling the spin-polarized emission from nearby emitters, as will be demonstrated experimentally. These results have practical implications for controlling the optical activity and can potentially enable new polarization-dependent light-emitting devices for applications in imaging, optical communication, and optical displays.