A parallel design scheme for ultra-compact silicon waveguide crossing based on the tapered multimode interference coupler

Abstract

We demonstrate two ultra-compact high efficiency silicon waveguide crossing devices based on the tapered multimode interference coupler in the entire wavelength range of 1520 to 1580 nm. A parallel waveguide crossing structure for transverse-electric (TE) mode with a footprint of only 1.05 × 2.6 μm2 is designed, which can provide single mode crossing with the insertion loss better than 0.12 dB and the crosstalk lower than −23 dB in the broadband. A polarization-insensitive waveguide crossing with a footprint of only 1.1 × 2.3 μm2 is also designed, which can provide insertion loss lower than 0.54 dB and crosstalk lower than −23 dB for both TE and transverse-magnetic modes. The proposed parallel crossing scheme can efficiently save rooms for building up sophisticated waveguide crossing networks by avoiding the waveguide bending before or after crossing. These devices can have great application potential in the dense photonic integrated systems.