Silica waveguide evanescent waves

A novel fiber optic sensor concept using antibody-antigen reactions at a glass-liquid interface was reported by Daehne146. The reaction of antibodies immobilized onto the surface of fused silica fiber optic or planar waveguides with antigens in solution was detected by interaction with the evanescent wave. By detecting in-line fluorescence, the measurement of human IgG is described. 

Demarco D.R., Lim D.V., Detection of Escherichia coli 0157 H7 in 10-and 25-gram ground beef samples with an evanescent-wave biosensor with silica and polystyrene waveguides, J. Food Protect. 2002 65 596-602. 

In another application of multiple position detection, a cooled CCD detector has been used to detect four spots of fluorescein-labeled HSA, which bind to anti-HSA antibody that is immobilized on a fused silica plate.(134) Irradiation of the waveguide at a 70° angle of incidence on the top surface generates an evanescent wave in the waveguide. The CCD is positioned parallel to the top surface of the waveguide to capture the emission of the labeled HSA. Three-dimensional images of the scans are shown in this study. 

The curing of an epoxy resin adj acent to an embedded silica optical fibre was monitored in situ by evanescent wave spectroscopy. The epoxy resin was partially fluorinated and had a lower refractive index than the silica fibre. The lower refractive index of the epoxy resin allowed the silica optical fibre to be used as a waveguide for the internal reflection of the near-IR light. The epoxy resin curing was determined as a function of time and temp, by analysis of the near-IR spectmm from the epoxy adj acent to the fibre obtained by the interaction of the evanescent wave that occurred at each internal reflection with the low refractive index epoxy resin. The results obtained showed that epoxy ring-opening and... 

Measurements with evanescent wave spectroscopy have been made, using both glass slides as a waveguide and optical fibres such as polymer-clad silica (PCS) fibre without the cladding. 

---