A Flow Cell for Mode-Specific, Integrated Optical Waveguide Spectroscopy in Aqueous Superstrates

Integrated optical waveguide (IOW) spectroscopy has attracted considerable interest as a technique for investigating physical and chemical processes at interfaces. The advantages of IO waveguides for interfacial studies include the extremely high irradiance that can be generated in the guide (usually achieved by efficient prism coupling); the higher reflection density in comparison to that for conventional internal reflection spectroscopies; and the discrete electric field distributions of resonant modes that are both spatially inhomogeneous and easily calculated. Swalen and co-workers exploited these features in studies of IO waveguide-excited Raman scattering from Langmuir-Blodgett (L-B) layers deposited on waveguide surfaces. Their reports yielded information on molecular adhesion mechanisms and surface orientation of the L-B structures, thus establishing IOW spectroscopy as a technique for studying interfacial chemistry of monolayer samples.