Symmetry and topology at the metasurface

• Main Author: Lawrence, Mark
• Published: University of Birmingham 2015
• Subjects: 621.36; QC Physics
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.665763

Since the metamaterials ethos of geometry over chemistry was first conceived at the end of the last century, a great deal of effort has been directed towards the conceptual, computational and experimental development of myriad effective electromagnetic media. Taking inspiration from quantum mechanics, here we exploit the possibility of independently controlling the individual elements of an effective polarizability matrix to reveal unique polarisation based phenomena. Firstly, by employing resonant “meta-atoms” to selectively absorb specific polarisation states of THz radiation, while tuning the polarisation conversion efficiency via near-field coupling, Parity Time symmetry breaking has been proposed, based on analytical and numerical modelling, and observed, using THz-Time Domain Spectroscopy, in polarisation space for the first time. We also reveal that anisotropic material as well radiative loss can be highly useful for tailoring the response of resonant metamaterials. Secondly, the possibility of achieving a topologically non-trivial phase within an effectively homogeneous photonic medium is discussed. Originating from the inherent spin-orbit interaction for light, three dimensional metamaterials with chirality and hyperbolicity are shown to be topologically non-trivial, resulting in one-way surface waves that are immune to back-scattering. Building on the effective medium calculations, our predictions are confirmed by numerical studies of realistic meta-structures.