University of Minnesota
Institute of Technology
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Electrical and Computer Engineering

Reflection-Based Bio-Sensing Using Integrated Optical Micro-Resonators

Terry Smith
3M, Corporate Research Materials Laboratory

Optical micro-resonators based on micro-spheres, tori, capillaries, and integrated optical cavities have
been widely investigated for optical bio-sensing applications. By coating the surfaces of these
structures with specific binding chemistries such as antibodies, and monitoring the resonant frequency
shift caused by the presence of the bound species within the device evanescent field, very low detection
limits can be achieved. However, most of the approaches investigated to date suffer from disadvantages
related to manufacturability, stability, or system cost. Here a new sensing approach incorporating micro-
resonators is presented that relies on the interaction of the evanescent field with metal nano-particle taggants. 
The nano-particles induce coupling between forward and backward modes propagating in the resonator; the
coupling results in a broadband intensity-encoded signal which can be detected using low-cost optoelectronics. 
Furthermore, this approach permits the use of simplified resonator device configurations that are compatible
with low-cost manufacturing approaches.

Terry L. Smith joined 3M in 1979, after receiving a Ph.D. in Physics from the University of Illinois, Urbana-
Champaign. His 3M career has included development of a variety of optoelectronic devices and systems,
including x-ray imagers, optical recording media, electro-photographic systems, ZnSe blue-green laser diodes,
lithium niobate integrated optical switches and fiber gyroscope chips, parallel fiber-optic data links, fiber-optic
Bragg gratings, dispersion compensation systems, and micro-mechanically self-aligned optical splitters for
Fiber-to-the-Home networks.  He currently leads the Optical Physics Group in the Corporate Research
Materials Laboratory, pursuing programs in integrated optical sensors and visible light-emitting devices.