Topology inverse design of integrated biosensors

In this work, and inspired by the multimode fiber refractive index sensors, we propose and design a refractive index sensor in a silicon-on-insulator (SOI) semiconductor structure using a complex multimode resonator. The resonator is optimized with an adjoint-based inverse design topology optimization technique using the commercial software Lumerical. We model the structure in a two-dimensional platform and the device's effective refractive index is calculated based on a suitable figure of merit. The sensor is tailored to operate within the telecommunication band, making it suitable for applications such as wearable devices for patient monitoring or detection of pathogens or toxins in environmental monitoring. The biosensor's design is optimized for maximum sensitivity to changes in the surrounding refractive index within the 1450 nm to 1650 nm wavelength range. It is also compatible with standard fabrication processes and the minimum manufacturable feature size, which is crucial for practical implementation.