This Paper introduces analyzing and modeling dual silicon-oxy-nitride [SiOxNy ] racetrack resonators(RRs) for biosensing applications. The geometric configuration of the resonators and design of alternative small sensing windows result in the realization of optical biosensors with a highly improved intrinsic limit of detection (ILOD). A small sensing window, located above the coupling region of dual RRs, can be used to maximize the total quality factor (minimized ILOD). The best characteristics for each optical component in the parallel-coupled RR-based biosensors are single-mode-channel waveguides with dimensions of 35 × 1 μm^2; the radius of curvature 90 μm and quality factors up to approximately 5.53 × 10^6 for RRs. The biosensing performance of our proposed configuration is compared with other experimental and simulated biosensor devices. Our structure shows an ILOD of approximately 1.81 ×10^−6 refractive index units (r.i.u.), which significantly improved 100 times compared with the traditional single SiOxNy RR biosensor. This ultra-improved ILOD parameter is found in the dynamic refractive index range of 1.332–1.350 r.i.u. It shows that the proposed biosensor could be a promising diagnostic candidate for analyzing different components of blood samples, which is especially important in the early detection of some critical diseases such as prostate cancer.
