Integrated photonic glucose biosensor using a vertically coupled microring resonator in polymers

A photonic glucose biosensor incorporating a vertically coupled polymeric microring resonator was proposed and accomplished. The concentration of a glucose solution was estimated by observing the shift in the resonant wavelength of the resonator. For achieving higher sensitivity the contrast between the effective refractive index of the polymeric waveguide and that of the analyte was minimized. Actually, the effective refractive index of the polymeric waveguide (n = similar to 1.390) was substantially close to that (n = similar to 1.333) of the fresh solution with no glucose. The fabricated resonator sensor with the free spectral range of 0.66 nm yielded a sensitivity of similar to 280 pm/(g/dL), which corresponds to similar to 200 nm/RIU (refractive index units) as a refractometric sensor, and provided a detection limit of refractive index change on the order of 10(-5) RIU. (C) 2008 Elsevier B.V. All rights reserved.