Topology Optimization-Based Design of Topological Edge-State Wavelength Division Multiplexer

Previous research processes on topological insulators were mainly based on the manual adjustment of a large number of fine parameters to achieve the desired properties. Here, we propose to treat the design process of photonic crystals as an objective function through topological optimization theory, allowing the desired properties to arise spontaneously with the optimization. Through topology optimization, we have designed and implemented three topological photonic crystals with different topological characteristics and dual-band protection common bandgap. The results show that functional edge modes with desired propagation properties can be generated within these two bandgaps by constructing domain walls between photonic crystal structures with different topological phases. The unidirectional transmission characteristics of the wave can also be observed, which provides an easy way to implement a wavelength division multiplexer.