Opt Quant Electron (2012) 44:557–562 DOI 10.1007/s11082-012-9557-0 INVITED PAPER Silicon photonic MZI sensor array employing on-chip wavelength multiplexing P. Muellner · R. Bruck · M. Baus · M. Karl · T. Wahlbrink · R. Hainberger Received: 21 October 2011 / Accepted: 25 January 2012 / Published online: 5 February 2012 © Springer Science+Business Media, LLC. 2012 Abstract In this work, we present a novel wavelength multiplexing concept for an integrated label-free biosensor array employing silicon photonic Mach-Zehnder interfer- ometers as sensors. Microring resonators act as wavelength selective elements in order to address the individual interferometers. Wire Bragg gratings terminate the interferometer arms and reflect the light back, which eliminates the risk of a wavelength mismatch between drop and add port. The characteristics of the device are discussed and the design based on FEM and 3D-FDTD simulations as well as measurements of the nanophotonic key components— micro ring resonators, Mach-Zehnder interferometers and photonic wire Bragg gratings—are presented. Measurements of combinations of the wire Bragg gratings with ring resonators and Mach-Zehnder interferometer sensors demonstrate the applicability of the reflectors in photonic circuits. Keywords Mach-Zehnder interferometer · Wire Bragg gratings · Ring resonators · Photonic sensor array · Silicon photonics · Biosensor 1 Introduction Mainly pushed by data- and telecom needs, silicon photonics is gradually entering other areas such as life science, where researchers start to exploit the high potential of integrated sili- con photonic sensors. Silicon-on-insulator (SOI) based biosensors allow real-time label-free measurements of biomolecular interactions. Moreover, they offer the possibility to realize multi-parameter measurements, which increases the diagnostic significance and accuracy. Integrated silicon photonic Mach-Zehnder interferometers (MZIs) have been widely inves- tigated as sensing elements for the detection of biomolecules (Densmore et al. 2009) due to their high sensitivity, which arises from the large ratio between waveguide length and P. Muellner (B ) · R. Bruck · R. Hainberger AIT Austrian Institute of Technology GmbH, Vienna, Austria e-mail: paul.muellner@ait.ac.at M. Baus · M. Karl · T. Wahlbrink AMO GmbH, Aachen, Germany 123