On-Chip Chemical Sensing Using Slot-Waveguide-Based Ring Resonator

We demonstrate static and dynamic bulk refractive index measurement using slot-waveguide based ring resonator. A detailed simulation is performed to optimize the slot-waveguide geometry for maximum sensitivity. The on-chip measurements are performed using a slot waveguide ring resonator by applying aqueous solutions of acids and bases at different concentrations. Based on these measurements, we derive a relation of refractive index change per unit change in concentration of the liquids in water. We experimentally measured a maximum sensitivity of 476 nm/RIU, enabling a limit of detection (LOD) of 1.05×10-5 RIU. Finally, we demonstrate dynamic refractive index on-chip measurement by diluting potassium bicarbonate with hydrogen peroxide.