A silicon-based athermal double-ring resonator biosensor with a vertically coupled configuration is developed. We present an optimal design of the sensor structure by specifying the radii of the reference and the sensing rings, the vertical coupling offset, d, between the two rings and the bus waveguide, and the lateral offset, l, between the edges of the rings and the bus waveguide. By using Lumerical software package, we demonstrate that the optimal vertical and lateral offsets are d=325 nm and l=-80 nm, respectively. One major challenge faced by ring based biosensors is their temperature dependent characteristics. In this study, the sensing ring is exposed to the biomaterial under test, while the reference ring provides a temperature-insensitive reference to the sensing measurements. By assuming the biomaterial medium has small variations in temperature, we conclude that the proposed biosensor device offers temperature insensitive measurement, where the temperature effects are fully corrected by the reference ring response. The double-ring sensors are proposed to be fabricated with the local oxidation of silicon process, without the need for advanced lithography methods such as e-beam or deep UV lithography. In addition, the vertically coupled double-ring configuration allows precise control of the critical coupling separation between the rings and the bus waveguide. The proposed silicon double-ring biosensor can be used for highly sensitive and stable sensing for both biomedical and environmental applications.

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Photonics North 2011
Department of Electronics

Xiong, Y. (Yule), & Ye, W.N. (2011). Vertically coupled Si-based athermal double-ring biosensor. In Proceedings of SPIE - The International Society for Optical Engineering. doi:10.1117/12.905392