Nature Communications

Pseudospin-valley coupled edge states in a photonic topological insulator

Pseudo-spin and valley degrees of freedom of electronic topological insulators can be emulated in photonic crystals..  This provides possible approaches to optical encoding and robust signal transport. In a recent article (Nature Communications 9, 3029 (2018)) we have introduced spin-orbit coupling into a meta-crystal with a rod and collar, while a trivial valley crystal is created in a lattice of triangular prisms. Along the interface between these domains, we observe a ballistic edge state whose spin-valley indices are locked to the direction of propagation. We demonstrate the inhibition of inter-valley scattering at a Y-junction formed at the interfaces between photonic topological insulators carrying different spin-valley Chern number. These results open up the possibility of using valley indices to control the flow of optical signals in 2D structures. The figure below shows side and top views of the structure.