Topological transmission and topological corner states combiner in all-dielectric honeycomb valley photonic crystals

We study the topological states (TSs) of all-dielectric honeycomb valley photonic crystals (VPCs). Breaking the space inversion symmetry of the honeycomb lattice by varying the filling ratio of materials for circular ring dielectric columns in the unit cell, which triggers topological phase transitions and thus achieves topological edge states (TESs) and topological corner states (TCSs). The results demonstrate that this structure has efficient photon transmission characteristics and anti-scattering robustness. In particular, we have found that changing the type of edge splicing between VPCs with different topological properties produces a change in the frequency of TCSs, and then based on this phenomenon, we have used a new method of adjusting only the type of edge splicing of the structure to design a novel TCSs combiner that can integrate four TCSs with different frequencies. This work not only expands the variety and number of unexplored TCSs that may exist in a fixed photonic band gap and can be rationalized to be selectively excited in the fixed configuration. Our study provides a feasible pathway for the design of integrated optical devices in which multiple TSs coexist in a single photonic system.