Topological edge states of Kekul\'e-type photonic crystals induced by a synchronized rotation of unit cells

TL;DR

This paper introduces a tunable 2D photonic crystal with Kekule9 lattice that uses synchronized rotation of unit cells to induce topological phase transitions, enabling robust edge states for defect waveguides.

Contribution

It presents a novel design of a Kekule9-type photonic crystal where synchronized rotation of pillars induces topological phase changes, a new method for reconfigurable topological photonics.

Findings

Rotation induces Dirac-degeneracy breaking and topological phase transition.

Topologically protected edge states enable robust waveguide transmission.

The scheme allows reconfigurable topological phases in photonic systems.

Abstract

Generating and manipulating Dirac points in artificial atomic crystals has received attention especially in photonic systems due to their ease of implementation. In this paper, we propose a two-dimensional photonic crystal made of a Kekul\'e lattice of pure dielectrics, where the internal rotation of cylindrical pillars induces optical Dirac-degeneracy breaking. Our calculated dispersion reveals that the synchronized rotation reverses bands and switches parity as well so as to induce a topological phase transition. Our simulation demonstrates that such topologically protected edge states can achieve robust transmission in defect waveguides under deformation, and therefore provides a pragmatically tunable scheme to achieve reconfigurable topological phases.