Mode division multiplexing on an InP membrane on silicon

A 5-channel mode division multiplexed on-chip optical bus is designed and demonstrated on a submicron-thick InP membrane wafer-bonded on a Si substrate. Dual-core adiabatic tapers are leveraged for realization of the mode (de)multiplexers. The optimized device shows low excess optical loss of maximum 0.14 dB compared to a reference waveguide and low crosstalk of maximum -18.5 dB for all 5 channels over a broad optical bandwidth of 1510 ~ 1600 nm. High fabrication tolerance to width variations is also demonstrated, where low excess loss of less than 1 dB and low crosstalk of less than -14 dB are maintained in 1530 ~ 1585 nm, covering the C-band, when the width varies by up to 50 nm. The demonstrated results show an essential step towards a monolithic photonic layer on top of electronic chips for high-capacity on-chip optical interconnects.