Planar Silicon-Polydimethylsiloxane Optofluidic Ring Resonator Sensors

We report an optofluidic ring resonator sensor based on liquid-core hybrid silicon-polymer waveguides. The device features a planar layout that combines optical and fluidic functions on the same platform. A high quality factor of $1.44\, \times \, 10^{4}$ is achieved. The device resonant wavelength shift has been measured as a function of the water-core temperature, obtaining a temperature sensitivity of 0.0633 nm/°C. Based on the thermo-optic effect of water, this corresponds to a bulk refractive index (RI) sensitivity of $\sim 700$ nm per RI unit (RIU), resulting in the RI limit of detection of $\sim 1.57\times 10^{\mathrm {-6}}$ RIU. The planar architecture combined with an optofluidic design concept holds the promise of high functionality and compactness toward a complete on-chip integrated sensing system.