Evanescent field sensing: optical nanofibres, whispering-gallery-mode microspherical and microbubble resonators

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dc.contributor.advisor Nic Chormaic, Síle en
dc.contributor.author Watkins, Amy Marie
dc.date.accessioned 2013-07-22T09:23:30Z
dc.date.issued 2013
dc.date.submitted 2013
dc.identifier.citation Watkins, A. 2013. Evanescent field sensing: optical nanofibres, whispering-gallery-mode microspherical and microbubble resonators. PhD Thesis, University College Cork. en
dc.identifier.uri http://hdl.handle.net/10468/1198
dc.description.abstract In this thesis, the evanescent field sensing techniques of tapered optical nanofibres and microspherical resonators are investigated. This includes evanescent field spectroscopy of a silica nanofibre in a rubidium vapour; thermo-optical tuning of Er:Yb co-doped phosphate glass microspheres; optomechanical properties of microspherical pendulums; and the fabrication and characterisation of borosilicate microbubble resonators. Doppler-broadened and sub-Doppler absorption spectroscopic techniques are performed around the D2 transition (780.24 nm) of rubidium using the evanescent field produced at the waist of a tapered nanofibre with input probe powers as low as 55 nW. Doppler-broadened Zeeman shifts and a preliminary dichroic atomic vapour laser lock (DAVLL) line shape are also observed via the nanofibre waist with an applied magnetic field of 60 G. This device has the potential for laser frequency stabilisation while also studying the effects of atom-surface interactions. A non-invasive thermo-optical tuning technique of Er:Yb co-doped microspheres to specific arbitrary wavelengths is demonstrated particularly to 1294 nm and the 5S1/2F=3 to 5P3/2Fʹ=4 laser cooling transition of 85Rb. Reversible tuning ranges of up to 474 GHz and on resonance cavity timescales on the order of 100 s are reported. This procedure has prospective applications for sensing a variety of atomic or molecular species in a cavity quantum electrodynamics (QED) experiments. The mechanical characteristics of a silica microsphere pendulum with a relatively low spring constant of 10-4 Nm-1 are explored. A novel method of frequency sweeping the motion of the pendulum to determine its natural resonance frequencies while overriding its sensitivity to environmental noise is proposed. An estimated force of 0.25 N is required to actuate the pendulum by a displacement of (1-2) μm. It is suggested that this is of sufficient magnitude to be experienced between two evanescently coupled microspheres (photonic molecule) and enable spatial trapping of the micropendulum. Finally, single-input borosilicate microbubble resonators with diameters <100 μm are fabricated using a CO2 laser. Optical whispering gallery mode spectra are observed via evanescent coupling with a tapered fibre. A red-shift of (4-22) GHz of the resonance modes is detected when the hollow cavity was filled with nano-filtered water. A polarisation conversion effect, with an efficiency of 10%, is observed when the diameter of the coupling tapered fibre waist is varied. This effect is also achieved by simply varying the polarisation of the input light in the tapered fibre where the efficiency is optimised to 92%. Thus, the microbubble device acts as a reversible band-pass to band-stop optical filter for cavity-QED, integrated solid-state and semiconductor circuit applications. en
dc.description.sponsorship Irish Research Council for Science Engineering and Technology (EMBARK) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2013, Amy Watkins en
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/ en
dc.subject Optical microresonators en
dc.subject Optical nanofibres en
dc.subject Atom-surface interactions en
dc.subject Evanescent field sensing en
dc.subject.lcsh Nanofibers en
dc.subject.lcsh Resonators en
dc.title Evanescent field sensing: optical nanofibres, whispering-gallery-mode microspherical and microbubble resonators en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD (Science) en
dc.internal.availability Full text not available en
dc.check.info Indefinite en
dc.check.date 10000-01-01
dc.description.version Accepted Version
dc.contributor.funder Irish Research Council for Science Engineering and Technology en
dc.description.status Not peer reviewed en
dc.internal.school Physics en
dc.internal.school Tyndall National Institute en
dc.check.reason This thesis is due for publication or the author is actively seeking to publish this material en
dc.check.opt-out Yes en
dc.thesis.opt-out true *
dc.check.entireThesis Entire Thesis Restricted
dc.check.embargoformat Both hard copy thesis and e-thesis en

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© 2013, Amy Watkins Except where otherwise noted, this item's license is described as © 2013, Amy Watkins
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