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

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Nanophotonics

Background:

• Traditional mode-division multiplexing (MDM) systems face polarization sensitivity bottlenecks.
• Efficiently separating different polarization modes is crucial for high-capacity optical communication.

Purpose of the Study:

• To propose and experimentally demonstrate a silicon-based dual-polarization mode splitter.
• To overcome the polarization sensitivity limitations of existing mode splitters.

Main Methods:

• Fabrication on a silicon-on-insulator (SOI) platform.
• Utilizing a subwavelength circular hole array as the functional core.
• Optimization using the direct binary search (DBS) algorithm.

Main Results:

• Achieved ultra-compact integration with a footprint of 5.1 × 2.4 µm².
• Simultaneous separation of TE₀/TE₁ and TM₀/TM₁ mode pairs without polarization preprocessing.
• Demonstrated low insertion losses (0.7–1.25 dB) and crosstalk below -10.9 dB across a 1500–1580 nm bandwidth.

Conclusions:

• This work presents the first dual-polarization mode splitter with orderless conversion, multi-polarization compatibility, and broadband operation.
• The developed device offers compact integration and high performance.
• It lays the foundation for next-generation optical interconnection systems.