Multimode silicon photonics using on-chip geometrical-optics

TL;DR

This paper introduces a geometrical-optics-inspired approach for on-chip multimode silicon photonics, enabling scalable, low-loss, and reconfigurable multimode components that simplify design and improve capacity for optical interconnects.

Contribution

It presents a universal, waveguide-width-based design method for multimode photonic devices, simplifying fabrication and enabling scalable, low-loss, reconfigurable multimode components.

Findings

Low-loss multimode waveguide crossings and bends achieved

Ultra-low power reconfigurable multimode switch demonstrated

Scalable design supporting larger mode channels

Abstract

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. Present on-chip multimode devices are based on traditional wave-optics. Although large amount 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 universal solution to standardize the design of fundamental multimode building blocks, by introducing a geometrical-optics-like concept adopting 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 demultiplexing procedure and ensuring compact footprint. Compare to 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. Low losses of multimode waveguide crossing and bend are achieved, as well as ultra-low power consumption of the multimode switch is realized since it enables reconfigurable routing for a group of modes simultaneously. Our work promotes the multimode photonics research and makes the MDM technique more practical.