Integrated photonic biosensors are capable of detecting trace amounts of biochemical substances without time-consuming labeling steps . Ring resonators and Mach-Zehnder interferometers (MZI) are among the most widely used sensor architectures. The latter can operate with a simple, fixed-wavelength source and have recently shown state-of-the-art limit of detections (LOD) (10−7 −10−8 RIU)  by using the coherent phase read-out illustrated in Fig. 1(a), overcoming sensitivity fading and directional ambiguity . Sensors using resonant structures often require a wavelength-swept source or broadband source combined with a spectrum analyzer . However, they can also be interrogated with a coherent detection scheme and a fixed wavelength source, shown in Fig. 1(b), making them especially suited for cost sensitive point-of-care devices.
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