A Novel Photonic Biosensor Based on Multi-Coupled Micro-ring Resonators: Design and Numerical Validation for Ultra-High Resolution Cancer Cell Detection

Early and accurate detection of cancer is essential for effective treatment and improved patient outcomes. Photonic integrated circuits (PICs) offer significant advantages for biosensing in cancer diagnostics due to their compactness, high sensitivity, and rapid response times. However, conventional cancer biosensors often rely on labeling mechanisms, which introduce complexity and reduce real-time efficiency. This work presents the design and numerical validation of a novel ultra-compact, label-free photonic biosensor based on multi-coupled microring resonators (MRRs). The proposed architecture employs a high-density coupling scheme that enhances light–matter interaction and resonance sharpness, enabling ultra-high-resolution cancer detection. This resolution is achieved through the constructive overlap and interference of tightly interwoven coupling paths within the resonator network. The sensor is specifically optimized to detect six cancer cell types—Basal (skin), MCF-7 and MDA-MB-231 (breast), PC12 (adrenal), HeLa (cervical), and Jurkat (blood)—based on an approximate refractive index contrast of 0.014 RIU compared to healthy cells. Finite element method (FEM) simulations over the 1515–1555 nm wavelength range demonstrate a sensitivity of approximately 45 nm/RIU, a full-width at half maximum (FWHM) below 0.005 nm, and exceptionally high quality factors (QF) ranging from 1.5 × 10 5 to 1.0 × 10 6. The corresponding figure of merit (FOM) reaches up to 27,000, significantly outperforming existing photonic biosensor designs. These results highlight the potential of the proposed PIC-based sensor as a high-performance, high-resolution, label-free platform for next-generation biomedical diagnostics.