Integrated Platform for Robust Differential Refractive Index Sensor

In this work, we demonstrate an integrated platform comprising a refractive index (RI) sensor based on Photonic Molecule (PM) that effectively mitigates the influence of environmental perturbations using a differential measurement scheme while providing high quality-factor (Q) resonances. The RI sensor consists of an exposed microdisk resonator coupled to an external clad microring resonator fabricated on silicon-on-insulator (SOI) platform. We report a RI sensitivity of 23 nm/RIU, achieving a limit of detection (LOD) of 1.6 x 10-3 refractive index units (RIU) with improved stability in a compact footprint of 40 x 40 {\mu}m2, representing a good solution for real-life applications in which measurement conditions are not easily controllable.