High performance SOI microring resonator for biochemical sensing

• We investigated different SOI microcavities based on a planar geometry with a footprint as small as 100 μm2 for biosensing devices.
• We demonstrated a Q factor of the order of 105, a LOD of the order of 10−6 RIU and a sensitivity of 120 nm/RIU.
• We designed the device for glucose biosensing.
• We proposed an on chip platform for high throughput, multichannel detection.

In this work we have investigated different silicon-on-insulator (SOI) microcavities based on a planar geometry having a footprint on chip as small as 100 μm2 with a ring, disk and hybrid configurations with the aim of being poorly intrusive for both in-body and out-of-body biosensing purposes. Accurate numerical results have been achieved by using the 3D finite element method and compared to 3D finite discrete time domain ones with a good agreement for both methods. The most promising resonator among the devices we have analyzed shows a Q-factor of the order of 105, that allows a limit of detection for the sensor equal to 10−6 RIU and a sensor sensitivity of 120 nm/RIU. The resonator has been designed for glucose biosensing, considering both the homogeneous sensing and the surface one, that enhances the sensor selectivity by the device functionalization with a glucose-oxidase (GOD) layer. The glucose concentration has been evaluated both with the microcavity surrounded by a water solution and with water only in the inner part of the cavity.The achieved performance is really attractive not only for the reduced size of the cavity, but also for the planar coupling configuration of the annulus and the waveguides composing the cavity since it appears to be a very promising configuration for the practical packaging of micro systems containing whispering gallery mode resonators. In this paper the concept of an on-chip platform for a high throughput and multichannel detection relying on an array of resonant cavities interacting with a single nanofluidic channel, is also discussed.