Interferometric sensor for detection of surface-bound bioreactions

An integrated optical interferometer for direct detection of affinity react ions is presented. A modern version of a Young's interferometer is built wi th a waveguide structure as beam splitter and as sensing element. Resistive waveguides were produced by plasma-enhanced chemical vapor deposition of s ilicon oxinitride. At the output of this device a fringe pattern is detecte d by a CCD line camera. The adsorption of molecules on top of the waveguide s is observed with a detection limit of 750 fg/mm(2). The resolvable variat ion of effective refractive index is 9 x 10(-8). (C) 2000 Optical Society o f America. OCIS codes: 130.6010, 130.6750, 230.3120, 230.7380.