Sci. Adv. 2, e1501168 (2016)

Metasurfaces are flat, ultrathin systems that can shape and manipulate light on length scales far smaller than those accessible with conventional optical components. Although potentially useful for optical device miniaturization, plasmonic metasurfaces often don't perform well when it comes to visible light. Fei Qin and colleagues have now shown that bilayer structures provide a route for manipulating visible light more efficiently.

Comprising arrays of metallic nanostructures, plasmonic metasurfaces shape light through its interaction with the plasmonic modes. Qin et al. looked at combining the response of an array of metallic elements with its inverse: a metallic film with an array of holes. By integrating a capacitive metasurface with an inductive one, they could manipulate the phase of cross-polarized transmitted light more efficiently than is possible with a single-layer plasmonic metasurface. So despite having much higher losses, metallic metasurfaces can be used to manipulate light with efficiencies similar to their dielectric counterparts.