Integrated bio/chemical microsystems employing optical detection: the clip-on

The fabrication and test of a new integrated optical detection circuit, which can be coupled to external microcapillary analysis systems, is presented. Simple optical waveguide and photodiode circuits, as well as the system for coupling light through the external microcapillary chemical transport system, are included on the same silicon, `clip-on', chip. A chemical reaction taking place in the external microcapillary system, which gives rise to a change in absorbance or luminescence, is detected as the reaction front moves past the optical detection circuit. Mesa photodiode structures are butt coupled to multilayer glass optical waveguides and have responsivities of about 0.5 plus a broad spectral response. The buried optical waveguide structures, which are formed in low loss (0.5 dB ) germanium doped core glass, couple very effectively to the mesa diodes. Light is coupled to the waveguides via optical fibers which are fastened to the chip by means of simple connectors etched into the silicon. Fluids are transported to and from the chip by means of quartz microcapillary, similarly fastened to the chip by means of an integrated connector.