Development of optomechanofluidic resonators
Optomechanofluidic resonators (OMFRs) supporting both high-optical Q factor whispering-gallery modes and high-mechanical Q factor optomechanical modes have recently emerged as a novel sensor configuration able to respond to mass density, mechanical compressibility, and viscoelasticity of label-free cells and particles at rates exceeding 10,000 cells/second in liquid with near-perfect capture efficiency and higher sensitivity than flow-cytometry-based techniques. Optomechanical systems efficiently couple photon and phonon modes and various nano/microscale geometries have been investigated to define their properties experimentally. However, significant acoustic radiative losses under liquid contact have restricted their use in liquid applications. On the other hand, the OMFR, fabricated from a hollow capillary, is intrinsically designed for microfluidic experiments. A simple method of simultaneously driving the resonator with continuous-wave light and observing the response of the system with a single evanescently-coupled tapered optical fibre is employed. This hybrid dual-resonant system consisting of an OMFR shell and contained fluid can be considered a radiation-pressure driven acoustic resonator. The optical modes do not significantly interact with the contained fluid directly, therefore neither the fluid nor (bio)analyte contribute to measurable optical changes. This thesis is concerned with researching experimentally the sensing principles of OMFRs. First, an apparatus for the fabrication of OMFRs from preform silica capillaries based on a carbon dioxide laser dual-beam heating method is developed. Second, an apparatus for the fabrication of single mode tapered optical fibres that employs a novel real-time Gabor transform monitoring method is developed. Third, the two components are integrated into an experimental apparatus for the observation of high-Q factor optical and mechanical modes in OMFR shells. Finally, an analysis towards developing a self-contained sensing platform capable of OMFR-like acoustic measurements is performed.
acoustic wave physics, characterisation, electrical engineering, evanescent coupling, fabrication, Gabor transform, noise, optics, optomechanics, optomechanofluidic resonator, physics, Q factor, sensing, short-time Fourier transform, signal processing, tapered optical fibre, time series analysis, whispering-gallery modes
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