Design of Compact Arbitrary-Ratio Multimode Power Splitters Based on Topological Derivative

Compact unbalanced splitters are a key constitutive block to achieve flexibility in future multimode applications relying on silicon-on-insulator technology. Their design, however, poses significant challenges as it has to combine high performance for the different supported modes, a compact size, and compliance with fabrication constraints. In this letter, we employ topological derivative to optimize the design of bimodal unbalanced splitters with predefined split ratios of 2:1 and 3:1. Numerical simulations reveal that the optimized devices achieve the desired ratios with insertion losses of 0.6 dB and 0.5 dB, and crosstalks of -18.2 dB and -16.4 dB, both in a compact footprint of 4.2 μm × 3.5 μm.