Coding photonic paths based on valley-protected topological phonic crystal

To achieve a flexible and reconfigurable topological edge state waveguide, we construct a valley photonic crystal (VPC) with liquid crystal filled rods. The permittivity of the two inequivalent rods in a unit is determined through the external voltage, which leads to a VPC with different valley topological phases. The external voltage is controlled by the codes of “0” and “1” on a control panel. Through programming the codes, arbitrary paths of topological edge states are achieved. The results were demonstrated by field propagation simulations.