Compact and broadband dual-polarization silicon mode splitter based on inverse design

To overcome the polarization sensitivity bottleneck of mode splitters in traditional mode-division multiplexing (MDM) systems, this study proposed and experimentally demonstrated a silicon-based dual-polarization mode splitter. Fabricated on a silicon-on-insulator (SOI) platform, the device adopts a subwavelength circular hole array as its functional core. Optimized via the direct binary search (DBS) algorithm, which converged after six iterations, the device achieved ultra-compact integration with a footprint of 5.1 × 2.4 µm². Without polarization preprocessing, it enables simultaneous separation of TE₀/TE₁ and TM₀/TM₁ mode pairs. Experimental results show that at 1550 nm, the insertion losses (IL) of TE₀ (TE₁) and TM₀ (TM₁) were 1.25 dB (0.7 dB) and 1.29 dB (1.09 dB), respectively, with corresponding crosstalk (CT) values of -21.54 dB (-19.3 dB) and -12.0 dB (-13.34 dB). Across the 1500-1580 nm wavelength range, the CT of all operating modes remains below -10.9 dB. To the best of our knowledge, this is the first reported dual-polarization mode splitter with orderless conversion, multi-polarization compatibility, compact integration, and broadband operation, which lays the foundation for the development of the next generation compact, high-performance, high-capacity optical interconnection systems.