Integrated optical sensors have become important in recent years since they are the only technology which allows the direct detection of biomolecular interactions. Moreover, silicon microelectronics technology allows mass production as well as the fabrication of nano-/macrosystems on the same platform by hybrid integration of sources, sensors, photodetectors and complementary metal-oxide semiconductor electronics.For the fabrication of an optical sensor nanodevice with an integrated Mach–Zehnder interferometric (MZI) configuration, the optical waveguides must have two main features: monomode behaviour and a high surface sensitivity. In this paper we present the development of a MZI sensor based on total internal reflection waveguides with nanometre dimensions. The aim is to use these sensors in environmental control to detect water pollutants by immunoassay techniques.

Silicon nitride photonics is on the rise owing to the broadband nature of the material, allowing applications of biophotonics, tele/datacom, optical signal processing and sensing, from visible, through near to mid-infrared wavelengths. In this paper, a review of the state of the art of silicon nitride strip waveguide platforms is provided, alongside the experimental results on the development of a versatile 300 nm guiding film height silicon nitride platform.

The performance of an interferometric device based on integrated Bimodal Waveguides (BiMW) for sensing is demonstrated. The sensors are fabricated using standard silicon technology and can achieve a detection limit of 2.5·10 -7 RIU for homogeneous sensing, rendering in a very high sensitive device. The applicability of the bimodal waveguide interferometer as label-free biosensor has been demonstrated by the real-time monitoring of the biomolecular interaction of BSA and anti-BSA. Due to their simplicity, the interferometric devices could be further integrated in complete lab-on-a-chip platforms for point-of-care diagnostics showing them as a powerful instrument for biochemical analysis.

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