Comparison between Vernier-cascade and MZI as transducer for biosensing with on-chip spectral filter

The Mach-Zehnder interferometer (MZI) and the Vernier-cascade are highly responsive photonic sensors with large design freedom. They are therefore very suitable for interrogation through a broadband source and an on-chip spectral filter, a sensing scheme that is well equipped for point-of-care applications. In this work, the MZI is shown to outperform the Vernier-cascade through a better minimum detectable wavelength shift as well as a higher power efficiency, indicating its superiority in this sensing scheme. Fabricated MZIs yield bulk detection limits down to 8.8×10−7 refractive index units (RIU) in a point-of-care compatible measuring setup, indicating the potential of the proposed sensing scheme.