Reconfigurable topological waveguide based on honeycomb lattice of dielectric cuboids

We show that the photonic crystal (PhC) made of dielectric cuboids with their centers forming a honeycomb lattice is characterized by a ℤ 2 ${\mathbb{ℤ}}_{2}$ topological index when the longer sides of six cuboids point towards the center of hexagonal unit cell. While the C 6v symmetry regarding the center of unit cell is preserved, the C 3 symmetry regarding honeycomb sites is broken, which opens a bandgap in the Dirac dispersion of honeycomb structure and induces a band inversion between p modes and d modes. Rotating cuboids around their individual centers closes the bandgap and reopens a trivial bandgap. We discuss that this feature can be exploited for realizing a reconfigurable topological waveguide.