Pseudospin topological behavior and topological edge states in a two-dimensional photonic crystal composed of Si rods in a triangular lattice

In this work we propose a two-dimensional topological photonic system of Si rods, whose unit cell is composed of six artificial atoms located on the sites of a triangular lattice. By perturbing the original lattice, by alternately increasing (type A) and shrinking (type B) the radius of the rods, we find edge modes that are highly localized at the interface between the type A and type B photonic crystals. The proposed structure is robust against complex defects and allows transmission of the propagating electromagnetic waves without any reflection. The interface edge modes present a typical behavior corresponding to that of a topological insulator. More specifically, the edge mode presents a pseudospin topological behavior. Our numerical results show the robustness, originating from the topological protection, of this mode against defects, disorder, and reflection. Also, the localization at the interface state permits the confinement of the light, where the interface behaves as a waveguide for the propagation of electromagnetic waves. The geometric perturbation considered here can easily be implemented using nanolithography.