Silicon-based microphotonics for biosensing applications

This paper reviews theory and experiments on silicon photonic wire waveguide evanescent field (PWEF) biosensors. Theoretical considerations and supporting calculations show that sensor response increases both with increasing core-cladding refractive index contrast, and with decreasing waveguide core thickness until a maximum sensor response is achieved. As a result, appropriately designed Si waveguide sensors can have the largest response to superstrate refractive index shifts, and also to surface molecular adsorption, of any commonly available waveguide system. Measurements of Si waveguide sensor response to fluid index change and biotin-avidin binding reactions confirm the predictions of theory.