Dual-mode waveguide crossing utilizing taper-assisted multimode-interference couplers.

A dual-mode waveguide crossing is proposed and realized for the application of on-chip multimode interconnection. The present structure is realized by two 90° crossed multimode-interference (MMI) couplers. By properly choosing the width and length of the MMI section, the self-images for both the incident TM₀ mode and the TM₁ mode could be at the center of the crossing. The characterization results for the fabricated device show that low insertion loss below ∼1.5  dB and low crosstalk below ∼-18  dB can be achieved over a large bandwidth more than 80 nm for both the TM₀ and TM₁ modes.