Investigation of topological valley kink states along zigzag and armchair domain wall in a two-dimensional photonic crystal

This paper provides a numerical analysis of the topological valley kink states along both zigzag and armchair domain walls of a dielectric two-dimensional photonic crystal (PC), considering the photonic energy band folding mechanism. By engineering the side length of triangular holes in a honeycomb PC, we created inequivalent valleys in the momentum space. We utilized two adjacent valley PCs with inverted structures to induce a topological transition of the TE mode energy band as it crossed the interface. Further research into the projected energy bands along both zigzag and armchair directions revealed that topologically protected valley kink states can be supported by both configurations. The zigzag interface enabled valley waveguides to transport chiral optical fields at the 0 degrees, 60 degrees, and 120 degrees bending angles, while maintaining their backscattering immune properties. The armchair interface, on the other hand, supported the straight propagation. By combining both armchair and zigzag interfaces, the valley waveguide can facilitate bending propagation at 90 degrees and 180 degrees, while also enabling the equal splitting of chiral fields at the intersection between these two interfaces. Our analyzation can be helpful to improve the applications of valley waveguides in integrated photonics.

Automated summary

This paper presents a numerical analysis of the topological valley kink states in a two-dimensional photonic crystal, focusing on both zigzag and armchair domain walls. By manipulating the triangular holes in a honeycomb structure, inequivalent valleys were created in the momentum space. The results showed that both the zigzag and armchair interfaces can support topologically protected valley kink states, providing potential applications for valley waveguides in integrated photonics.