Asymmetric Y junctions in silicon waveguides for on-chip mode-division multiplexing

Silicon waveguide asymmetric Y junction mode multiplexers and demultiplexers are demonstrated for applications in on-chip mode-division multiplexing (MDM). We measure demultiplexed crosstalk as low as -30 dB, <-9 dB over the C band, and insertion loss <1.5 dB for multimode links up to 1.2 mm in length. The frequency response of these devices is shown to depend upon Y junction angle and multimode interconnect length. Interference effects are shown to be advantageous for low-crosstalk MDM, even while using compact Y junctions designed to be outside the mode-sorting regime.