Interferometric sensor for detection of surface-bound bioreactions

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Abstract
An integrated optical interferometer for direct detection of affinity reactions is presented. A modern version of a Young’s interferometer is built with a waveguide structure as beam splitter and as sensing element. Resistive waveguides were produced by plasma-enhanced chemical vapor deposition of silicon oxinitride. At the output of this device a fringe pattern is detected by a CCD line camera. The adsorption of molecules on top of the waveguides is observed with a detection limit of 750 fg/mm2. The resolvable variation of effective refractive index is 9 × 10-8.