Topological metasurfaces for symmetry-protected electromagnetic line waves

Dia'aaldin J. Bisharat; Daniel F. Sievenpiper

doi:10.1117/12.2529727

5 September 2019 Topological metasurfaces for symmetry-protected electromagnetic line waves

Dia'aaldin J. Bisharat, Daniel F. Sievenpiper

Proceedings Volume 11080, Metamaterials, Metadevices, and Metasystems 2019; 110800Q (2019) https://doi.org/10.1117/12.2529727
Event: SPIE Nanoscience + Engineering, 2019, San Diego, California, United States

Abstract

The discovery of topological condensed-matter systems has promoted extensive research on analogous classical photonic systems, motivated by the prospect of backscattering-immune wave propagation. So far, photonic topological insulators have mainly relied on engineering bulk modes in photonic crystals and waveguide arrays in two-dimensional systems. However, these realizations suffer from bulky structures, intricate design/material requirements, or limited operational bandwidth. Here, we present symmetry-protected topological states akin to quantum spin-Hall and valley-Hall effects by engineering surface modes over open-boundary metallic metasurfaces of infinitesimal thickness. As a result, the proposed structures support robust gapless edge states, which are confined and guided along a one-dimensional line rather than a surface interface. To emulate the spin degree of freedom, we exploit the electromagnetic-duality symmetry by stacking two complementary metasurfaces. Straightforwardly, the modal degeneracies are formed at high-symmetry K/K′ points due to the use of hexagonal unit cells, while the strong effective magneto-electric coupling inherent to the overlapped metasurfaces opens a wide non-trivial bandgap. To emulate the valley degree of freedom, on the other hand, we exploit the mirror symmetry of the structure by reducing the lattice symmetry of the hexagonal cell-based metasurface, which has either inductive or capacitive response, into C3υ point symmetry. Consequently, the degeneracy between the two valleys in reciprocal space is lifted. Owing to the simplicity, compactness, tunability, and openboundary nature of the proposed system, it constitutes an attractive tabletop platform for the study of classical topological phases, as well as for practical applications advancing the potential of photonic topological insulators.

Conference Presentation

Citation Download Citation

Dia'aaldin J. Bisharat and Daniel F. Sievenpiper "Topological metasurfaces for symmetry-protected electromagnetic line waves", Proc. SPIE 11080, Metamaterials, Metadevices, and Metasystems 2019, 110800Q (5 September 2019); https://doi.org/10.1117/12.2529727

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available