Improving Topological Confinement Using Asymmetric Elements

Abstract

Photonic topological systems are enticing alternatives to realize multifunctional optical circuits with minimum distortions due to their unique insulating features. Among them, expanded honeycomb structures give rise to topological phases without involving any external field or gyromagnetic materials. Unlike atoms in crystals, the morphology of the repeating element in photonic systems can be tailored, allowing to tune the different interelement couplings. In this regard, traditional circular rods are replaced in honeycomb lattices with teardrop‐shaped pillars to push the “center of mass” outward, thus heightening the intercell interaction. This teardrop honeycomb lattice can provide a broader nontrivial bandgap and better edge‐state confinement compared with a circular rod lattice with the same material‐to‐void filling factor. The approach proposes a novel method to tailor the performance of topological systems by engineering the individual pillars and results in better‐confining waveguides that can be building blocks for designing more compact optical circuits under the same platform.