Racetrack ring resonator-assisted MZI-based integrated optical biosensor with buffer layers for measuring blood glucose level.

In this study, we present a two-racetrack ring assisted Mach-Zehnder interferometer (RRAMZI) configuration, specifically engineered for glucose detection. RRAMZI chose to combine the property of high sensitivity of the racetrack ring resonator (RRR) with the property of high accuracy due to the reference arm of the Mach-Zehnder Interferometer(MZI) for achieving high sensitivity with high accuracy. To enhance biosensor performance, intermediate buffer layers were introduced between the core and substrate layers. Depending on the material chosen for the buffer layer, it offers the advantage of enhancing the resonant and penetration depths. In this paper, two different configurations of RAMZI with two different buffer materials are presented. The two materials of the buffer layer are silicon nitride (Si3N4) and fluorinated silicon dioxide (FSiO2). The first Si3N4 buffer layer is strategically introduced between the silicon dioxide (SiO2) substrate and the silicon (Si) core. The inclusion of the Si3N4 layer directly contributes to an increase in resonant depth, which eventually enhances the quality factor to 1.435× 103. In the second architecture, the FSiO2 layer is introduced between SiO2 and Si. It enhances penetration depth, which in turn increases the sensitivity of RRAMZI to 400 nm/ RIU. The system is analytically modeled using the signal-flow graph (SFG) method.