Quantitative Terahertz Communication Evaluation of Compact Valley Topological Photonic Crystal Waveguides

Topologically protected edge modes can effectively navigate turns and are immune to backscattering, making them widely applicable in compact routing designs for on-chip photonic systems. However, the influence of evanescent waves at topological boundaries between adjacent topological waveguides on the communication signal quality remains underexplored. In this paper, we experimentally study the quantitative relationship between the thickness of the domain wall and the communication quality of valley topological photonic crystal (VPC) waveguides on all-silicon chips within terahertz communication systems. As the thickness of the domain wall gradually decreases, the signal error initially increases and then decreases. Key evaluation parameters, including bit error rate, constellation diagrams, and eye diagrams, support this trend. Crosstalk between evanescent waves in adjacent topological waveguides can significantly impact the communication quality of intrachip signals due to the varying proportions of guided and evanescent wave components. These findings provide critical technical support for achieving high-quality communication through compact and dense routing based on VPC waveguides. The mutual coupling of evanescent waves between adjacent waveguides in terahertz valley topological photonic crystal on-chip circuits significantly affects communication quality, which is closely linked to the optical wiring configuration. This study quantitatively examines the relationship between the spacing of adjacent waveguides and communication quality, while also exploring the physical mechanism underlying this phenomenon.