Large-Area Photonic Topological Waveguides with Wide Operating Bandwidths

Topological states constructed using photonic topological insulators (TIs) have garnered significant attention due to their exceptional wave modulation properties. Generally, topological edge states typically form at the interface between two domains of trivial and nontrivial photonic crystal (PhC) unit cells, which limits the capacity of transmissions and the interfacing with existing bulk devices in applications. Current studies have achieved large-area topological waveguide states by inserting gapless unit cells between trivial and nontrivial unit cells. However, as the width of the waveguide increases, the operating band tends to be significantly narrowed. In this research, we propose heterostructures with intermittently coupled topological waveguides capable of realizing broadband large-area waveguides while maintaining robustness against structural defects. Simulation results verify that the device is capable of flexible and adjustable wave transmission. The device can realize large-area photonic waveguides with operating bandwidths of approximately 4 GHz. This structure holds the potential for the design of multifunctional, strongly robust, and highly flexible topological devices.