Ultra-broadband multimode fiber-to-chip edge coupler based on periodically segmented waveguides.

Mode-division multiplexing (MDM) technology demonstrates a bright outlook for enhancing the capacity of chip-scale or fiber-based optical communication. Nevertheless, the fiber-to-chip MDM optical interconnects are hindered by the considerable mode mismatch and inter-modal cross talk between the few-mode fiber (FMF) and on-chip few-mode waveguide (FMW). In this Letter, a new, to the best of our knowledge, multimode coupling solution based on periodically segmented waveguides for the MDM system is proposed, which achieves efficient conversion between LP, LP, and LP modes in FMF and E, E, and E modes in FMW with low refractive index difference.