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

¹ Telecommunication Research Institute (TELMA), Universidad de Málaga, CEI Andalucía TECH, E.T.S.I. Telecomunicación, 29010 Málaga, Spain
² IBIMA Plataforma BIONAND, Parque Tecnológico de Andalucía, 29590, Málaga, Spain
³ Scuola Superiore Sant’Anna, Institute of Mechanical Intelligence, Via G. Moruzzi 1, 56124, Pisa, Italy
⁴ Scuola Superiore Sant’Anna, Institute of Biorobotics, Viale Rinaldo Piaggio 34, 56025, Pontedera, Italy
⁵ BIOHERENT, S.L., Calle Severo Ochoa, 34, 29590, Málaga, Spain

^* Corresponding author: asr@ic.uma.es

Published online: 31 October 2024

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.