Design and optimization of integrated multimode interferometers (MMIs) for dual-polarization photonic biosensors for biomedical applications in a silicon-on-insulator platform

Multimode Interferometers (MMIs) have long served as essential components in low-loss beam-splitters and -combiners for applications in advanced communications, neuromorphic computing, and interferometric imaging. Recent advancements in photonic integrated circuits position MMIs as promising candidates for biosensing applications, enabling highly sensitive detection of biomolecules critical biomedical. This study presents the first design and optimization of integrated MMIs on a silicon-on-insulator (SOI) platform specifically tailored for advanced biosensor applications. Our device demonstrates sensitivity comparable to established MRRs and MZIs, with the added benefits of CMOS manufacturability and improved reproducibility. Utilizing both the fundamental TE and TM modes allows for enhanced measurement reliability by differentiating evanescent field penetration depths. Furthermore, our integration strategy, which incorporates microfluidic channels through local backside etching, enables compact, high-density sensor designs, paving the way for cost-efficient, wafer-scale production of photonic sensor chips.