Fundamental limits in high-Q droplet microresonators

Year: 2017

Authors: Giorgini A., Avino S., Malara P., De Natale P., Gagliardi G.

Autors Affiliation: INO, Consiglio Nazl Ric, Via Campi Flegrei 34,Complesso A Olivetti, I-80078 Naples, Italy; INO, Consiglio Nazl Ric, Largo E Fermi 6, I-50125 Florence, Italy.

Abstract: Liquid droplet whispering-gallery-mode microresonators open a new research frontier for sensing, optomechanics and photonic devices. At visible wavelengths, where most liquids are transparent, a major contribution to a droplet optical quality factor is expected theoretically from thermal surface distortions and capillary waves. Here, we investigate experimentally these predictions using transient cavity ring-down spectroscopy. With our scheme, the optical out-coupling and intrinsic loss are measured independently while any perturbation induced by thermal, acoustic and laser-frequency noise is avoided thanks to the ultra-short light-cavity interaction time. The measurements reveal a photon lifetime at least ten times longer than the thermal limit and indicate that capillary fluctuations activate surface scattering effects responsible for light coupling. This suggests that droplet microresonators are an ideal optical platform for ultra-sensitive spectroscopy of highly transparent liquid compounds in nano-liter volumes.

Journal/Review: SCIENTIFIC REPORTS

Volume: 7      Pages from: 41997-1  to: 41997-7

More Information: The experimental work was supported by the P.O.R. Campania FESR 2007-2013 project titled \”BERSAGLI\”. The authors are grateful to G. Notariale for technical assistance.
KeyWords: whispering galery modes, droplets, microresonators, surface scattering, thermal noise
DOI: 10.1038/srep41997

Citations: 29
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