Topological Slow Light Rainbow Trapping and Releasing Based on Gradient Valley Photonic Crystal

Slow light topological photonic crystal waveguide offers an attractive platform for enhancing light-matter interaction. We design a slow light rainbow trapping based on translational valley photonic crystal waveguides constructed by a gradient interface width. Through theoretical analysis and numerical calculation, the resulting structure supports topologically protected edge states at different frequencies. The edge state can be slowed down to zero group velocity and trapped at different positions. Moreover, the switch between slow light trapped states and transport states can be easily realized by tuning the structural parameter. Our work can help open up a new avenue to control the flow of light and find great potential for applications such as optical buffers and wavelength-division multiplexing.