Low-loss and low-cross talk polarization-insensitive multimode silicon waveguide crossing.

A polarization-insensitive multimode silicon waveguide crossing is investigated and experimentally characterized in this Letter. By employing the particle swarm optimization (PSO) algorithm and finite difference time domain (FDTD) method, the lengths and widths of the waveguides in the proposed device are optimized for attaining wide bandwidth, small insertion loss (IL), low cross talk (CT), and compact size. Measurement results reveal that the footprint of the presented device is 11.92 μm × 11.92 μm. From 1520 to 1600 nm, the measured insertion loss and cross talk are smaller than 0.67 dB and -28.6 dB in the case of the TE mode, lower than 0.65 dB and -28.7 dB in the case of the TE mode, less than 0.48 dB and -36.3 dB in the case of the TM mode, and lower than 0.62 dB and -28 dB in the case of the TM mode.