Rainbow trapping based on gradient Kagome topological photonic crystals and one-dimensional arrays

Topological edge states with different frequencies located at different positions are called as the topological rainbow trapping effect. The topological rainbow capture has been studied extensively over the past years. In this work, for the first time to the best of our knowledge, we propose to realize the topological rainbow trapping based on the gradually shrinking and expanding the two-dimensional Kagome lattice. In order to simplify the topological structure, the one-dimensional array instead of the expanding Kagome lattice can also achieve the topological rainbow capture. In addition, the frequencies of rainbow trapping are modulated by the distance from the one-dimensional array to the Kagome lattice. The spatial positions of rainbow trapping at a fixed frequency are very sensitive to the dielectric constants of the environment and of dielectric columns, so we envisage potential applications in the area of topological sensors.