Mode division multiplexing using chip-scale silicon coupled vertical gratings

Mode division multiplexing of modes in a silicon waveguide supporting three optical modes is demonstrated in the silicon on insulator platform. Cross-talk suppression of 17dB and 12dB are obtained for the zeroth and second order modes respectively. The extinction bandwidth is observed to increase with the mode order indicating a stronger cross coupling coefficient as the mode order is increased. The extinction ratio is also observed to increase from 5 dB to 15dB and >25dB as the mode order is increased, implying an increasing cross coupling coefficient.