Numerical analysis of Mach-Zehnder interferometer based optical sensors incorporating WGM ring resonator

This work presents an effective design of Mach-Zehnder Interferometer (MZI) based optical sensor having whispering gallery mode (WGM) ring resonator (RR), where RR is coupled in the MZI's sensing arm and acts as a sensing window. The unique feature of WGM-RR facilitates both spectral and phase response when the target biological particle interacts with the incoming light in the WGM-RR. The optical and geometric parameters of the proposed MZI based optical sensor are numerically investigated and optimized accordingly to make the biosensor suitable for the effective detection of analytes refractive index (RI) in any biological samples. Detailed investigation reveals that the MZI would achieve higher sensitivity in detecting analytes RI with optimized design parameters having simplified structural architecture. The optimized WGM-RR based MZI biosensor shows phase and wavelength sensitivities of 307.43 nm/RIU and 4348π/RIU, respectively with 14.56 μm long sensing arm. These two sensitivity parameters ensure the analytes RI more accurately compared to the conventional waveguide based-MZI.