Towards compact integrated refractive index sensors

Silicon on insulator (SOI) technology is desirable for implementing integrated photonic devices due to compatibility with standard fabrication techniques. In addition, the large refractive index contrast between the silicon layer and substrate (silicon dioxide) allows for the creation and control of confined photonic modes. In this work, we use topology optimization to create compact integrated sensors using SOI technology at telecommunication wavelengths. Our sensors utilize high-quality factor resonances to detect small variations in the refractive index of the surrounding medium, manifested through a shift in the resonance frequency. Furthermore, we utilize a custom three- to two-dimensional transformation along with topology optimization, which significantly reduces the computational cost of the design process. Our proposed platform is easy to implement, tunable to different wavelengths, and provides high sensitivity, making it suitable for biosensing and environmental monitoring applications.