High performance SOI microring resonator for biochemical sensing

In this work we have investigated different silicon-on-insulator (SOI) microcavities based on a planar geometry having a footprint on chip as smal las 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 thedevices we have analyzed shows a Q-factor of the order of 105, that allows a limit of detection for the sensor equal to106 RIU and a sensor sensitivity of 120nm/RIU. The resonator has been designed for glucose biosensing, considering both the homogeneous sensing and the surface one, that enhances the sensors electivity 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 microsystems containing whispering gallery mode resonators. In this paper the concept of a non-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.