Arrays of SOI photonic wire biosensors for label-free molecular detection

We present an SOI biosensor microarray chip that allows multiple molecular binding reactions to be simultaneously monitored. The individual biosensors are formed using 0.26 × 0.45 mum2 silicon photonic wire waveguides, which are arranged in compact Mach-Zehnder interferometer geometries with near temperature independent response. The sharp bend radius permitted by the photonic wires is exploited to form dense spiral waveguide structures that provide several millimeters of path length in a compact 130 mum diameter circular area. This design provides the high sensitivity of a long waveguide, while maintaining compatibility with commercial microarray spotting tools. For low volume analyte delivery the sensor array chip contains a monolithically integrated microfluidic channel formed in an SU-8 overlayer. Multiple antibody-antigen reactions are observed in real-time by using an infrared camera to monitor the optical powers emerging from the sensor array output waveguides.