Enhanced sensitivity in an engineered hybrid plasmonic ring resonator for ultra-compact, high-performance biosensing

Early-stage detection of cancer is crucial for improving survival outcomes; however, conventional diagnostic approaches are often limited by bulky instrumentation, labeling requirements, and high costs. In this work, we present an engineered hybrid plasmonic–dielectric ring resonator with an optimized geometry tailored for high-sensitivity, on-chip, label-free cancer detection. The sensing principle relies on monitoring refractive index variations caused by the interaction of circulating cancer cells with the evanescent field, thereby inducing a measurable shift in the resonant wavelength. The optimized geometry of the device plays a central role in enhancing performance, as it maximizes the overlap of the evanescent field with the analyte while maintaining strong optical confinement within a compact footprint. The device employs a hybrid plasmonic waveguide (HPW) configuration, integrating silicon (Si) and silver (Ag) to couple photonic and plasmonic modes. This design yields strong field confinement at the metal–dielectric interface and significantly improves light–matter interaction. The optimized structure achieves a sensitivity of 468.47 nm/RIU with an ultra-compact footprint of 6×6µm 2 , nearly doubling the sensitivity of a conventional Si-based RR (259 nm/RIU, 6×6µm 2 ). Benchmarking against state-of-the-art optical biosensing mechanisms further highlights its competitive edge in detection resolution and device miniaturization. This study underscores the importance of geometric optimization in hybrid plasmonic–dielectric architectures for achieving high sensitivity, establishing the proposed device as a promising platform for on-chip, point-of-care cancer diagnostics.