Cryogenic Optomechanics with Silica Microresonators

  • Author / Creator
    MacDonald, Allison J. R.
  • Cavity optomechanical devices are interesting systems for probing quantum mechanical behaviour of mesoscopic objects. A basic requirement for these types of experiments is preparation of the mechanical resonator in, or at least very close to, its ground state. Although active laser cooling techniques can help this process, conventional cryogenic (pre-)cooling is nonetheless necessary. This thesis introduces a custom-made apparatus, housed on the base plate of a commercial dilution refrigerator, for coupling light into an optomechanical resonator via a tapered optical fiber. Our system incorporates full three-dimensional control of the taper-resonator coupling conditions, enabling critical coupling at cryogenic temperatures. It also features an optical microscope which permits in situ imaging and alignment of the taper and resonator, while causing minimal heating to the environment. Optomechanical measurements of silica bottle resonators, which exhibit optical whispering gallery modes and high-quality mechanical breathing modes, are performed using the dilution fridge system. Several methods for enhancing the detection of small mechanical signals are tested and a method for determining the temperature of the mechanical mode is described and implemented. The tight confinement of light circulating in the bottle resonator leads to increased optical absorption and significant heating of the silica, which manifests itself in both the optical and mechanical properties of the resonator. We present the first measurements of these resonators for mechanical mode temperatures as low as 4 K, and fridge temperatures down to 9 mK.

  • Subjects / Keywords
  • Graduation date
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
    • Department of Physics
  • Supervisor / co-supervisor and their department(s)
    • Davis, John (Physics)
  • Examining committee members and their departments
    • LeBlanc, Lindsay (Physics)
    • Hegmann, Frank (Physics)
    • Freeman, Mark (Physics)
    • Davis, John (Physics)