We exploit the unique properties of the silicon-on-insulator material platform to demonstrate a new series of planar
waveguide evanescent field sensors for biological / chemical sensing. These sensors, combined with state-of-the-art
surface functionalization chemistries, offer a sensitive, label-free means for the specific detection of biomolecules,
without the need for fluorescent tags employed in conventional fluorescence-based biochips. The use of silicon photonic
wire waveguide technology allows sensors with extremely small footprint and small radius of curvature to be fabricated,
facilitating the development of densely packed sensor arrays for multi-parameter analysis, particularly attractive for drug
discovery, pathogen detection, genomics and disease diagnostics.
We show that high index contrast silicon photonic wire waveguides not only provide the above stated advantages but
also offer increased sensitivity over that of evanescent field sensors constructed on other common waveguide material
platforms. This results from the unique properties of the optical modes of silicon photonic wire waveguides, which
exhibit very large surface electric field magnitude and strong localization near the waveguide surface. We discuss the
design and fabrication of silicon-on-insulator-based Mach-Zehnder interferometer sensors and experimentally
demonstrate their performance to detect bulk solution refractive index change and to monitor the specific adsorption of
streptavidin to biotinylated waveguides.