Demonstration of a highly efficient multimode interference based silicon waveguide crossing

We present the design, fabrication and characterization of a highly efficient silicon waveguide crossing based on multimode interference (MMI). The crossing is formed by only one step etching with the grating couplers on a silicon-on-insulator (SOI) platform. High transmission efficiency of 98.5% (loss of −0.07 dB) and low crosstalk (<−43 dB) are predicted by the 3D FDTD simulation. Our experiment results showed good agreement with the simulation and, loss of −0.1 dB per crossing, and crosstalk better than −40 dB was obtained over a broad optical spectrum from 1520 nm to 1580 nm. Such a low loss, low crosstalk waveguide crossing is suitable for future on-chip optical interconnect.