Key Multimode Silicon Photonic Devices Inspired by Geometrical Optics

On-chip optical interconnect has been widely accepted as a promising technology to realize future large-scale multiprocessors. Mode-division multiplexing (MDM) provides a new degree of freedom for optical interconnects to dramatically increase the link capacity. For present on-chip multimode devices, although large amounts of computation and optimization are adopted to support more modes, mode-independent manipulation is still hard to be achieved due to severe mode dispersion. Here, we propose a promising solution to standardize the design of fundamental multimode building blocks, inspired by the geometrical-optics concept, adopting a waveguide width larger than the working wavelength. The proposed solution can tackle a group of modes at the same time with very simple processes, avoiding a demultiplexing procedure and ensuring compact footprint. Compared to the conventional schemes, it is scalable to larger mode channels without increasing the complexity and whole footprint. As a proof of concept, we demonstrate a set of multimode building blocks, including crossing, bend, coupler, and switches, with low loss and power consumption. Our work promotes the multimode photonics research and makes the MDM technique more practical.