Silicon nitride waveguide integration platform for medical diagnostic applications

The impressive progress of silicon photonic integrated device technology during the past fifteen years has been primarily driven by the requirements of optical data- and telecommunication. Research and development in silicon photonics has therefore been focused on the telecom wavelengths in the 1.55 µm and 1.31 µm regions and on silicon-on-insulator (SOI) material as waveguide integration platform. The rising cost burden of the traditional healthcare system as well as the increasing health consciousness among people is stimulating the decentralization of healthcare and is creating a strong demand for novel medical diagnostic devices suitable for point-of-care testing. This opens up new possibilities for integrated nanophotonic sensing devices operating in the visible and < 1.1 µm near infrared region. In this talk, we will present our ongoing research activities on the development of a CMOS-compatible photonic integrated circuit technology platform. This platform relies on silicon nitride waveguides fabricated by low-temperature plasma enhanced chemical vapor deposition (PECVD), which allows their monolithic co-integration with silicon photodiodes and CMOS based electronic read-out circuitry. We have achieved propagation losses of less than 1 dB/cm at a wavelength of 850nm in silicon nitride waveguides processed directly on an optoelectronic CMOS chip employing chemical-mechanical planarization (CMP). We will present the design and experimental validation of various nanophotonic building blocks required for the implementation of medical diagnostic sensing devices. We will show results of optical biosensing experiments based on integrated Mach-Zehnder interferometers and demonstrate how inkjet material printing technology can be effectively used to locally functionalize the optical waveguide transducer components. Moreover, we will discuss the potential of this silicon nitride waveguide based nanophotonic integration platform for the miniaturization of optical coherence tomography systems.