Compact and low-crosstalk silicon-based polarization-insensitive multi-channel and multi-mode waveguide crossing

A silicon-based polarization-insensitive multi-channel and multi-mode waveguide crossing is presented, optimized, and validated experimentally in this paper. The device structure is optimized to achieve polarization insensitivity, compact footprint, low crosstalk, small insertion loss, and wide bandwidth through the combined application of the particle swarm optimization algorithm, direct-binary-search optimization algorithm, and finite-difference time-domain method. Our presented device is found to exhibit a size of only 13.6 µm × 13.6 µm. The crosstalk and insertion loss in the case of the TE₀, TM₀, TE₁, or TM₁ modes are measured to be lower than -21.1 dB and 1.40 dB, -26.1 dB and 0.90 dB, -20.8 dB and 1.80 dB, or -20.4 dB and 1.70 dB from 1520 to 1600 nm, respectively.