Surface sensitivity of SiON integrated optical waveguides (IOWs) examined by IOW-attenuated total reflection spectrometry and IOW-Raman spectroscopy

A series of Langmuir-Blodgett (LB) films doped with increasing amounts of lipophilic cyanine dye were deposited at the surface of SiON waveguides. Propagation losses of incoupled laser light were measured photometrically, and then modeled using an attenuated total reflection (ATR) version of the Beer-Lambert law. The SiON waveguides exhibit an experimentally measured surface sensitivity of approximately 0.033 cm-1 propagation loss per 1012 dyes cm-2 and a detection limit of 8.4 × 1011 dyes cm-2. However, the experimental surface sensitivity was 0.4 times less than that predicted by ATR theory that did not account for scatter losses and dye aggregation in the LB film. The discrimination of small signals above background was demonstrated by collecting the integrated optical waveguide Raman spectrum of a submonolayer of avidin bound to the SiON waveguide surface through a biotin linker. This spectrum is believed to be the first spontaneous Raman spectrum reported for a protein film bound to a dielectric substrate. © 1994.

Duke Scholars

Author William M. Reichert Biomedical Engineering