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Proceedings Paper

Optofluidic whispering gallery mode microcapillary lasers for refractive index sensing
Author(s): Alexandre François; Nicolas Riesen; Kristy Gardner; Tanya M. Monro; Al Meldrum
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Paper Abstract

Whispering gallery modes (WGMs) allow for remarkable refractive index sensing performance with extremely low detection limits, and thus have found use in various emerging label free biosensing applications. Among the different types of resonators which have been studied, microcapillaries have the unique property of having the evanescent fields extend into and sample the medium inside the resonator, which is particularly interesting because the resonator itself serves as a microfluidic channel.

Here, lasing of the WGMs in fluorescent microcapillaries is demonstrated for the first time, and their application to refractive index sensing is investigated. The laser gain medium used here is embedded inside a high refractive index polymer coating deposited onto the inner surface of the capillary. Lasing can only be realized for thick polymer coatings (in this case ≥ 800 nm), with higher Q factor but also stronger confinement of the propagating wave, which lowers the refractive index sensitivity compared to non-lasing capillaries which can have thinner polymer coatings. We however find that the large improvement in signal-to-noise ratio and Q factor realized upon lasing more than compensates for the reduced sensitivity, resulting in an order-of-magnitude improvement in the detection limit for refractive index sensing.

Paper Details

Date Published: 9 December 2016
PDF: 8 pages
Proc. SPIE 10013, SPIE BioPhotonics Australasia, 100131E (9 December 2016); doi: 10.1117/12.2242705
Show Author Affiliations
Alexandre François, The Univ. of Adelaide (Australia)
The Univ. of South Australia (Australia)
Nicolas Riesen, The Univ. of Adelaide (Australia)
The Univ. of South Australia (Australia)
Kristy Gardner, Univ. of Alberta (Canada)
Tanya M. Monro, The Univ. of Adelaide (Australia)
The Univ. of South Australia (Australia)
Al Meldrum, Univ. of Alberta (Canada)

Published in SPIE Proceedings Vol. 10013:
SPIE BioPhotonics Australasia
Mark R. Hutchinson; Ewa M. Goldys, Editor(s)

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