An Ultracompact Multimode Waveguide Crossing Based on Subwavelength Asymmetric Y-Junction

We propose and experimentally demonstrate a novel ultracompact multimode waveguide crossing. The compact asymmetric subwavelength Y-junction is introduced to convert the high-order modes into fundamental ones, enabling one to implement three or more modes simultaneously in the subsequent processing. Our proposed device occupied only a compact footprint of 34 × 34 μm2. The measured results indicate our fabricated device exhibited a high performance with the insertion loss less than 0.9 dB, crosstalk lower than -24 dB from 1.52 to 1.60 μm for all the three modes. Moreover, our scheme could be easily expended to implement more modes and will show great potential in dense and large-scale on-chip photonic integration.