Monolithic silicon interferometric optoelectronic devices for label-free multi-analyte biosensing applications

Miniaturized bioanalytical devices find wide applications ranging from blood tests to environmental monitoring. Such devices in the form of hand held personal laboratories can transform point-of-care monitoring provided miniaturization, multianalyte detection and sensitivity issues are successfully resolved. Optical detection in biosensors is superior in many respects to other types of sensing based on alternative signal transduction techniques, especially when both sensitivity and label free detection is sought. The main drawback of optical biosensing transducers relates to the unresolved manufacturability issues encountered when attempting monolithic integration of the light source. If the mature silicon processing technology could be used to monolithically integrate optical components, including light emitting devices, into complete photonic sensors, then the lab on a chip concept would materialize into a robust and affordable way. Here, we describe and demonstrate a bioanalytical device consisting of a monolithic silicon optocoupler properly engineered as a planar interferometric microchip. The optical microchip monolithically integrates silicon light emitting diodes and detectors optically coupled through silicon nitride waveguides designed to form Mach-Zehnder interferometers. Label free detection of proteins is demonstrated down to pM sensitivities.