Silicon photonic microring resonators offer an ultra‑compact, label‑free platform for translating minute refractive‑index perturbations into easily tracked resonance shifts. This invited lecture surveys the fundamental physics of all‑pass and add‑drop configurations, with emphasis on confinement, group index engineering, quality factor management, and the coupled trade‑offs that ultimately define sensitivity and detection limits. Within this framework I will contextualise my doctoral contributions, beginning with a systematic comparison of multiple waveguide geometries in SOI technology, including strip, slot, PANDA and S‑junction designs, working at 1550 nm. Finite‑element modelling and experimental validation identified the slot ring as the most effective refractometric transducer, owing to its enhanced evanescent‑field overlap and favourable balance between propagation loss and optical confinement.

Building on these insights, the research migrated to a silicon nitride platform at 1310 nm, leveraging reduced material absorption to achieve substantially higher quality factors and correspondingly lower intrinsic detection limits under microfluidic operation. Surface functionalization with oriented monoclonal antibodies then converted optimized slot cavities from generic refractometers into robust biosensors. Assays targeting spike and fusion proteins from clinically relevant respiratory viruses demonstrated selective, real‑time monitoring of binding kinetics, while preserving specificity in the presence of complex sample matrices.

Finally, the methodology was validated using unprocessed nasopharyngeal swab extracts, achieving diagnostic concordance with reference molecular techniques and highlighting the robustness of the photonic interface. The talk concludes by outlining routes toward large‑scale multiplexing, integrated fluidic handling and fibre‑to‑chip packaging, positioning microring resonators as a scalable foundation for near‑patient infection surveillance and broader lab‑on‑a‑chip applications.