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Sensors 2015, 15(4), 8968-8980; doi:10.3390/s150408968

Stand-Off Biodetection with Free-Space Coupled Asymmetric Microsphere Cavities

Max Planck Institute for the Science of Light, Laboratory of Nanophotonics & Biosensing, Guenther-Scharowsky-Str. 1/Bldg. 24, Erlangen D-91058, Germany
Authors to whom correspondence should be addressed.
Academic Editor: Frances Ligler
Received: 21 November 2014 / Revised: 9 April 2015 / Accepted: 10 April 2015 / Published: 16 April 2015
(This article belongs to the Special Issue Advances in Optical Biosensors)
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Asymmetric microsphere resonant cavities (ARCs) allow for free-space coupling to high quality (Q) whispering gallery modes (WGMs) while exhibiting highly directional light emission, enabling WGM resonance measurements in the far-field. These remarkable characteristics make “stand-off” biodetection in which no coupling device is required in near-field contact with the resonator possible. Here we show asymmetric microsphere resonators fabricated from optical fibers which support dynamical tunneling to excite high-Q WGMs, and demonstrate free-space coupling to modes in an aqueous environment. We characterize the directional emission by fluorescence imaging, demonstrate coupled mode effects due to free space coupling by dynamical tunneling, and detect adsorption kinetics of a protein in aqueous solution. Based on our approach, new, more robust WGM biodetection schemes involving microfluidics and in-vivo measurements can be designed. View Full-Text
Keywords: Whispering Gallery Mode (WGM) biosensors; free-space coupling; asymmetric resonant cavities; biosensing; label-free detection; protein adsorption Whispering Gallery Mode (WGM) biosensors; free-space coupling; asymmetric resonant cavities; biosensing; label-free detection; protein adsorption

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Ballard, Z.; Baaske, M.D.; Vollmer, F. Stand-Off Biodetection with Free-Space Coupled Asymmetric Microsphere Cavities. Sensors 2015, 15, 8968-8980.

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