Ultralow Loss Waveguide Crossing with Low Imbalance for Two Transverse Electric Modes

Ultra-low loss waveguide crossings are requisite in the on-chip mode-division-multiplexing (MDM) system. We propose an ultra-low loss waveguide crossing using a combination of strip and rib waveguides in the multimode-interference (MMI) coupler region to reduce the imbalance for two transverse electric (TE) modes. Simulated results show that the insertion losses (ILs) are 0.043 and 0.084 dB for the fundamental TE polarized mode (TE
₀
) and the first-order TE polarized mode (TE
₁
) at 1550 nm, respectively. The ILs are <; 0.87 dB and <; 0.54 dB for TE0 and TE
₁
modes from 1500 to 1600 nm, respectively. The crosstalk (CT) is <; -50 dB for both modes within the 100 nm bandwidth.