Metasurface Reconfiguration through Lithium-Ion Intercalation in a Transition Metal Oxide

In the latest years the optical engineer's toolbox has welcomed a new concept, the metasurface. In a metasurface, the properly tailored material inclusions are able to reshape the electromagnetic field of an incident beam. Change of amplitude, phase, and polarization can be addressed within a thickness of only a fraction of a wavelength. By means of this concept, a radical gain in compactness of optical components is foreseen, even of the most complex ones; other unique features like that of analog computing have also been identified. With this huge potential ready to be disclosed, lack of tunability is still a main barrier to be broken. Metasurfaces must now be made reconfigurable, i.e., able to modify and memorize their state, possibly with a small amount of energy. In this Communication we report low-energy, reversible, and self-holding metasurface reconfiguration through lithium intercalation in a vanadium pentoxide layer integrated within the photonic device. By a proper meta-atom design, operation on amplitude and phase of linearly polarized light has been demonstrated. In addition, manipulation of circularly polarized light in the form of tunable chirality and tunable handedness-preserving reflection has been implemented. These operations, which can potentially be performed on the time scale of a fraction of a second, are accomplished using as low as ?50 pJ/?m^2, raising lithium intercalation in transition metal oxides as one of the most energy efficient self-holding tuning mechanisms known so far for metasurfaces, with significant perspectives in the whole field of nanophotonics.