(Invited) Optical Biosensors in Photonic Integrated Circuits for Smart System Integration

Abstract

Photonic integrated circuits (PIC) are like electronic integrated circuits drivers of communication systems. Moreover, state-of-the-art technologies enable the fabrication of electronic-photonic integrated circuits (ePIC), which allows for example the cointegration of ultra-fast BiCMOS devices with high speed photo detectors. Besides that, this technology provides an attractive platform for biosensors. They open the door for label-free detection of various analytes with high specificity and in real-time. This gives perspective to highly scalable and cost effective technologies for smart system integration of biosensors and electronic readouts to realize a true lab-on-a-chip application.We present the integration of optical biosensors in a Si-based PIC-technology. This comprises a front-end of line with optical waveguides, an integrated Ge-photodiode and a complete back-end of line consisting of three thin and two thick aluminum metal layers. The optical biosensor is integrated by opening the optical waveguide from the backside of the chip. In particular, we released a Si-based slot waveguide, which provides an enhanced evanescent field to interact with the analyte and hence to increase the sensitivity. The slot waveguide is incorporated in a ring resonator and we analyzed the wafer-level performance using the full width at half maximum, which allows us to assess the optical losses. Thermal sensing in a wide temperature range is investigated. In addition, a simple and cost-effective microfluidic is realized and we show initial results of the surface functionalization. Our work demonstrates the compatibility of a photonic biosensor with a photonic integrated circuit technology without any restriction to the standard FEOL and BEOL processing on the wafer front-side, while it keeps the inherent high sensitivity of evanescent-field sensing and opens a route towards smart system integration. Figure 1