Polarization-Independent Compact Waveguide Crossing on SOI Platform

As artificial intelligence systems scale, the demand for high-speed and energy-efficient chip continues to grow. Silicon photonics presents a compelling solution, particularly through dual-polarization schemes that utilize both transverse electric (TE) and transverse magnetic (TM) modes to double data throughput. However, designing polarization-independent components, such as waveguide crossings, on the standard 220 nm top silicon platform pose significant challenges. In this work, we experimentally demonstrate a compact, polarization-independent waveguide crossing enabled by an inverse design methodology using particle swarm optimization. The device achieves insertion loss below -0.18 dB and crosstalk better than -30 dB for both TE and TM modes across the full O-band (1260-1310 nm), with a compact footprint of only 8 μm × 8 μm. These performance metrics surpass those of previously reported devices with similar functionalities. Furthermore, the structure is fully compatible with standard commercial silicon photonics foundry processes. These results highlight the potential of inverse design to overcome polarization-related limitations in silicon photonics and enable dense, scalable, and high-performance optical interconnects for next-generation photonic systems.