Scalable selective mode filter architecture with asymmetric directional coupler

We propose a novel design architecture to realize scalable selective mode filter based on the asymmetric directional coupler structure. In this structure, any arbitrary high-order mode can pass, whereas other unwanted modes are blocked. Furthermore, multiple optical modes can be blocked by only adjusting the structural parameters. As a proof of concept, we experimentally demonstrated a three-mode device and the scalability of the proposed structure is demonstrated by another design of four-mode filter. The proposed architecture offers scalability and high-design flexibility, and it has excellent potential to be used in advanced mode division multiplexing optical networks.