Integration of vertical grating couplers and microfluidic channels with silicon photonic wire biosensor arrays

We describe a new label-free biosensor array chip developed for the real-time, simultaneous monitoring of multiple molecular binding reactions. It is composed of monolithically integrated grating couplers, microfluidic channels and spiral cavity silicon photonic wire sensors. The grating couplers use a novel design for coupling to the transverse magnetic mode of a silicon photonic wire. They contain arrays of subwavelength dimension holes, which allow the local refractive index to be engineered in the grating region. They can be fabricated with the photonic wires in a single etch step, an important advantage over other vertical couplers. The coiled waveguides are configured as ring resonators with extended cavity length for high sensitivity and small footprint for compatibility with microarray spotting. For analyte delivery, microfluidic channels were formed in an SU-8 overlayer.