Rainbow trapping and releasing based on the topological photonic crystals and a gradient 1D array

Abstract

Topological photonic crystal provides a platform for robust energy transport in photonic systems. In this letter, we propose a method for realizing rainbow trapping and releasing based on the topologically protected defect modes in dielectric photonic crystals. The photonic states of different frequencies are separated and trapped at different positions to form the topological rainbow. The all-dielectric planar nanostructures consist of deformed honeycomb lattices and a gradient 1D array, which is distinct from previous platforms where edge states appear at the interface between trivial and nontrivial crystals. Due to the simplification of the configuration, we can selectively control the stop position of the wave by modifying the bottom row of dielectric rods so that light can switch between the trapping state and releasing state. The robustness of the slowing light system is also investigated. These results are beneficial to multiple frequency tuning. The simplified structure could offer a novel method for micro-miniaturizing and applying optical communication equipment, such as optical storage and optical buffer.