Non-spin-mixing defect modes in the split-ring dielectric photonic crystals

Topological photonic crystals (PCs) with unique optical performances have tremendous potential application in the realm of integrated photonic circuits. In this paper, we propose split-ring topological PCs manufactured by conventional silicon material, which hosts both topological transition and helical edge states mimicking the quantum spin Hall effect. A large nontrivial bandgap from 224.85 THz to 235.03 THz can be achieved. Non-spin-mixing defect modes with the nature of topological protection are demonstrated when line defects are introduced by fabricating the sectional columns with Al2O3 at the interface of two different topologies. A guide path for the non-spin-mixing defect modes reveals that light can propagate unidirectionally with high efficiency, powerful optical localization, and strong stability. This work provides a versatile method to improve the performances of optical transmission and reveals a novel mechanism to guide light transmission, which has vast application prospects in the all-optical integrated circuits.