Photonic Topological Insulators Based on Metamaterials: Molding the Flow of Light Around Corners and Obstacles
Speaker: Gennady Shvets, University of Texas at Austin
Abstract: Photonic crystals have been referred to as “semiconductors of light” because of the far-reaching analogies between electron propagation in a crystal lattice and light propagation in a periodically modulated photonic environment. However, this analogy was never completed because photonic crystals could not emulate the electron spin. I will demonstrate how the emulation of both the spin and the spin-orbit coupling (SOC) is enabled by bi-anisotropic metamaterials. The importance of the SOC is that it makes possible the emergence of topologically nontrivial phases in condensed matter physics that give rise to topologically protected edge states immune to scattering. I will describe how the analogous photonic topological insulators (PTIs) emerge in metamaterials-based structures and enable topologically protected transport of electromagnetic waves. As the result, the fundamental limitation of light transport imposed by the wave equation, i.e. the inability of reflections-free light propagation along sharply bent pathway, can be circumvented. Topologically protected electromagnetic states could be used for transporting photons without any scattering, potentially underpinning new revolutionary concepts in applied science and engineering.
I will also describe a simple photonic structure, a periodic array of metallic cylinders attached to one of the two confining metal plates, that behaves as a PTI: possesses a complete topological bandgap and emulates spin-orbit interactions. An interface between two such structures supports topologically protected surface waves which can be guided without reflections along sharp bends of the interface. Perspectives on how metamaterials can emulate condensed-matter phenomena such as valleytronics, quantum spin Hall effect, and quantum Hall effect, will be presented.