Effects of structure parameters on kink states of two-dimensional valley photonic crystals

Abstract

We construct graphene-like valley photonic crystals (VPCs) by breaking spatial inversion symmetry in two-dimensional (2D) all-dielectric photonic crystals with honeycomb lattice. By tuning sizes of two scattering rods in unit cell, variations of topological band gaps of VPCs are investigated in detail. Further, valley-locked kink states and their unidirectional propagations are numerically studied by constructing two kinds of zigzag waveguide interfaces between two VPCs with opposite valley Chern number. Our results show that changing structure parameters of VPCs can effectively tune topological band gaps, adjust configurations of valley kink states, and control their unidirectional propagations, and particularly in some cases, resonant structures along waveguide interface can even destroy the valley-locked unidirectional propagations of kink states. We also investigate transverse localizations of kink states and reveal their robustness as they propagate along the interfaces. Our research gives further understandings on properties of VPCs, provides detailed regulation of kink states with change of structure parameters and paves the way for design of photonic devices based on VPCs.