Highly compact 2×2 multimode interference coupler in silicon photonic nanowires for array waveguide grating demodulation integration microsystem

A highly compact 2×2 multimode interference (MMI) coupler based on silicon-on-insulator that can be used in an array waveguide grating demodulation integration microsystem is designed. The coupler is simulated using the beam propagation method. Taper waveguides are used as input/output waveguides. The footprint of the MMI region is only 6 μm×57 μm. The excess loss is 0.46 dB, and the uniformity is 0.06 dB with transverse electric polarization when the center wavelength is 1.55 μm. The maximum excess loss is 1.55 dB in the range of 1.49 μm–1.59 μm. The simulation results show that a small 2×2 MMI coupler exhibits low excess loss, wide bandwidth, and good uniformity suitable for the requirements of the system on chip.

► A smaller dimension of 2×2 MMI coupler based on SOI for AWG demodulation integration microsystem is proposed.
► Under the condition of the similar footprint of multimode region, the 2×2 MMI coupler designed in the current work has lower excess loss.
► The 2×2 MMI coupler designed in the current work has wider bandwidth.
► The 2×2 MMI coupler designed in the current work has good uniformity.