Coexistence of slow light states and valley-polarized kink states in all-dielectric valley photonic crystals with triangular lattice

Topological photonic valley-Hall states, regarded as an excellent information carrier, have attracted a great attention in recent years due to binary degree of freedom (DOF) of valley states. In order to enhance and promote miniaturization and functionalization of integrated photonic devices using the valley DOF, researchers have performed a plethora of wok in both theory and experiment recently. In this work, we theoretically propose a kind of all-dielectric valley photonic crystals (VPCs) with triangular lattice composed of silicon rods, and systematically analyze and investigate two different domain interfaces (bearded-stack and zigzag-stack) constructed by the VPCs with opposite valley Chern numbers. Topological valley-Hall states, such as valley-polarized kink states and slow light states, are demonstrated and realized in the two domain interfaces, such as valley-polarized kink states in the low gap and slow light states in the high gap for the bearded-stack, and valley-polarized dual-band kink states and slow light states in the high gap for the zigzag-stack. Both the slow light states and the valley-polarized kink states have their own merits in the zigzag and bearded interfaces, respectively, e.g., valley-polarized dual-band kink states with broadband and high-energy-density light filed in the zigzag-stack, and slow light states with group-dispersionless and large group index in the bearded-stack. Additionally, the waveguide interfaces could be arbitrarily shifted by sliding and translating half lattice constant along X axis. Hence they can be easily manipulated and automatically controlled by external coding in practice application. Finally, our work provides a novel platform for applications in topological on-chip photonic devices with multifunction and specific light fields with field enhancement and high-energy-density transport.