Pseudospin-Polarized Topological Line Defects in Dielectric Photonic Crystals

Electromagnetic (EM) topological insulators have been extensively explored due to the robust edge states they support. In this work, we propose a topological EM system based on a line defect in topologically nontrivial photonic crystals (PCs). With a finite-difference supercell approach, modal analysis of the PC structure is investigated in detail. The topological line-defect states are pseudospin polarized and their energy flow directions are determined by the corresponding pseudospin helicities. These states can be excited by using two spatially symmetric line-source arrays carrying orbital angular momenta. The feature of the unidirectional propagation is demonstrated and it is stable when disorders are introduced to the PC structure.