Inverse-designed waveguide superlattices for ultra-broadband polarization-independent power splitters

Conventional waveguide superlattices rely on theoretical physics models with manual refractive index tuning to control light propagation, yielding limited design freedom and poor scalability. Here, we propose a universal design framework using inverse-designed waveguide superlattices and demonstrate a 1 × 2 polarization-insensitive power splitter. The designed device exhibits an ultra-broad bandwidth (1450-1650 nm) with insertion losses below 0.26 dB for both TE₀ and TM₀ modes. Fabricated via a CMOS-compatible process, the splitter experimentally achieves insertion loss <0.31 dB and power imbalance <0.24 dB over 1485-1635 nm. This design strategy is further extended to a 1 × 4 splitter with excellent polarization insensitivity and broadband performance, thus confirming the universality of the proposed superlattice approach and providing a novel, to the best of our knowledge, paradigm for developing next-generation photonic devices.