Journal article
Designing photonic topological insulators with quantum-spin-Hall edge states using topology optimization
Designing photonic topological insulators (PTIs) is highly non-trivial because it requires inversion of band symmetries around the band gap, which was so far done using intuition combined with meticulous trial and error. Here we take a completely different approach: we consider the design of PTIs as an inverse design problem and use topology optimization to maximize the transmission through an edge mode past a sharp bend.
Two design domains composed of two different but initially identical C6ν-symmetric unit cells define the geometrical design problem. Remarkably, the optimization results in a PTI reminiscent of the shrink-and-grow approach to quantum-spin-Hall PTIs but with notable differences in the crystal structure as well as qualitatively different band structures and with significantly improved performance as gauged by the band-gap sizes, which are at least 50% larger than in previous designs.
Furthermore, we find a directional β-factor exceeding 99% and very low losses for sharp bends. Our approach allows the introduction of fabrication limitations by design and opens an avenue towards designing PTIs with hitherto-unexplored symmetry constraints.
Language: | English |
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Publisher: | De Gruyter |
Year: | 2019 |
Pages: | 1363-1369 |
ISSN: | 21928614 and 21928606 |
Types: | Journal article |
DOI: | 10.1515/nanoph-2019-0057 |
ORCIDs: | Christiansen, Rasmus E. , Wang, Fengwen , Sigmund, Ole and Stobbe, Søren |