Ultralow Crosstalk and Loss CMOS Compatible Silicon Waveguide Star-Crossings with Arbitrary Included Angles

As the integration level of silicon photonics improves, using a large number of 2 × 2 crossings is seemingly inevitable. However, with the help of a multiports crossing, which has low crosstalk and loss, the number of crossings can be greatly reduced, then the integration density and routing flexibility can be enhanced. Here, we propose and demonstrate the novel 3 × 3, 4 × 4, 5 × 5 and 6 × 6 silicon waveguide star-crossings based on self-imaging. The star-crossings are fabrication compatible with the 180 nm commercial CMOS process. The fabricated devices show ultralow crosstalk and insertion loss. The crosstalk of those crossings are less than −50, −50, −49.2, and −48 dB, respectively, in C-band. The corresponding insertion loss are less than 0.067 dB, 0.075 dB, 0.081 and 0.133 dB, respectively. We also propose the high performance star-crossings with arbitrary angles, which can reduce the difficulty of the waveguide routing and further improve the integration density of photonics IC. The footprint and minimum angle of the proposed star-crossing are also discussed. The crossings have high fabrication tolerance, and will be widely used in the future integrated photonics.