|Abstract:||Cavity optomechanics experiments parametrically couple the phonon modes and photon modes in microresonators and various optical systems have been investigated. However, because of the increased acoustic radiative losses during direct liquid immersion of optomechanical devices, almost all published optomechanical experiments have been performed in solid phase. The high acoustic losses during direct liquid immersion limits the biosensing applications of optomechanical devices.
This thesis discusses a recently introduced hollow opto-mechano-fluidic resonator (OMFR), which by design are equipped for microfluidic experiments.
By confining liquids inside the capillary resonator, high mechanical- and optical- quality factors are simultaneously maintained. Unlike optofluidics biosensing, because the optical modes don't interact with the liquids directly, the optomechanical biosensing doesn't have any requirement of the optical properties of the fluids and bioanalytes.
Detailed methodology is provided to fabricate these ultra-high-Q microfluidic resonators, perform optomechanical testing, and measure radiation pressure-driven breathing mode (10--20 MHz) and SBS-driven (10--12 GHz) whispering gallery mode vibrations.
We also experimentally investigate aerostatic tuning of these hollow-shell oscillators, enabled by geometry, stress, and temperature effects. We demonstrate for the first time the simultaneous actuation of RP-induced breathing mechanical modes and SBS-induced whispering gallery acoustic modes, through a single pump laser.
In addition, we show that fluid viscosity can also be determined through optomechanical measurement of the vibrational noise spectrum of the resonator mechanical modes.
A linear relationship between the spectral linewidth and root-viscosity is predicted and experimentally verified in the low viscosity regime.
Our result is a step towards completely self-referenced optomechanical sensor technologies and multi-frequency measurement of viscoelasticity of arbitrary fluids and bioanalytes, without sample contamination, using highly sensitive optomechanics techniques.