Engineering of closely packed silicon-on-isolator waveguide arrays for mode division multiplexing applications

On-chip optical communications require high-performance, energy-efficient, and scalable multiplexing techniques for enabling high parallelism. Mode division multiplexing (MDM) is gaining momentum, but its scalability is limited by the crosstalk and the (de)multiplexing complexity. To overcome such limitations, this paper proposes the exploitation of super-modes in closely spaced arrays of waveguides. A theoretical approach demonstrates the generation of super-modes achieved by perturbing the uniformity of waveguide arrays. Spectral characterization shows a crosstalk of about -20 dB on the C band, in a nonuniform array of five silicon-on-isolator waveguides.