Visible Light Emitting Si-Rich Si3N4$\mu$-Disk Resonators for Sensoristic Applications

We demonstrate the high potential of an optical integrated sensor which monitors the changes of the effective refractive index of the resonant optical modes induced by variations of the refractive index of the surrounding material. The detection system is a CMOS compatible structure based on a visible light emitting Si-rich Si3N4 $\mu$-disk coupled to a passive Si3N4 waveguide placed underneath. We present a complete optical characterization of the active material in the isolated ($\mu$-disk) and combined (plus coupled waveguide) photonic systems. The material has been optimized to obtain bright cavities with high quality factors. As a final result, we demonstrate that the sensor can achieve a sensitivity of 36 nm/RIU for small refractive index changes ($\Delta$n$=$ 0.002) and a minimum detection limit of 1.6 \texttimes 10-3 RIU. This structure can be used as a building block for detection systems with increased complexity, in which demultiplexing and detection could be readily integrated on the same chip.