Abstract
We propose an inverse-designed ultra-compact rib waveguide power splitter that enables scalable and flexible 1×N power distribution on a standard silicon-on-insulator platform. By combining a binary optimization algorithm with three-dimensional finite-difference time-domain simulations, 1×2, 1×3, and 1×4 power splitters are successfully designed and validated. The multimode interference sections measure only 1.4×1.4, 2.1×2.1, and 2.8×2.8 μm2. The insertion losses of the 1×2, 1×3, and 1×4 splitters are all below 0.29 dB for the tested splitting ratios (1:1, 2:3, 1:2; 1:1:1, 1:2:1; 1:1:1:1, 1:2:2:1). All splitters maintain high spectral flatness over an 80 nm bandwidth (1510 to 1590 nm), and the insertion loss fluctuation remains below 0.05 dB under ±10 nm (∼8.3% for diameter, ∼7.7% for depth) fabrication deviations, demonstrating strong process robustness. We provide an efficient and reliable technological pathway toward ultra-compact, broadband, low-loss 1×N arbitrary-ratio optical power splitters.