Dual-polarization photonic integrated biosensor in a Mach-Zehnder interferometer with coherent phase readout

Abstract

Photonic integrated biosensors have garnered considerable attention due to their promising applications in various fields such as healthcare. Differentiating specific targets from interfering background effects is a challenging task. In this work, a dual-polarization Mach-Zehnder interferometer (MZI) with coherent phase readout is proposed to identify refractive index changes from different layers above the waveguide surface, thus improving sensor specificity. All the system building blocks have been designed for a 300 nm-thick silicon nitride platform, fabricated and characterized. The first experimental results show a bulk waveguide sensitivity of 0.17 RIU/RIU for TE polarization and 0.25 RIU/RIU for TM, confirming the correct functioning of the sensors when operating for each polarization separately. Future work will focus on simultaneous sensing with both polarizations and experiments with layered variation of refractive indices.