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.
ACCESS THE FULL ARTICLE
Alexandre François, Nicolas Riesen, Kristy Gardner, Tanya M. Monro, Al Meldrum, "Optofluidic whispering gallery mode microcapillary lasers for refractive index sensing," Proc. SPIE 10013, SPIE BioPhotonics Australasia, 100131E (9 December 2016);