Towards quantum applications of buckled dome microcavity devices

  • Author / Creator
    Bu, Lintong
  • This thesis describes the theory, fabrication, and characterization of monolithic integrated
    membrane-in-the-middle (MIM) optomechanical Fabry-Perot resonators and elliptical
    birefringent Fabry-Perot optical resonators. Both types of devices were fabricated on a silicon
    wafer using a thin-film buckling self-assembly technique.
    The MIM optomechanical cavity work follows that of a previous student, who had
    developed a method for releasing a free-standing silicon nitride (SiN) membrane embedded in a
    buckled dome microcavity, by using a surface micromachining (sacrificial etching) approach. In
    the present work, an improved photolithography method and an improved PECVD recipe for SiN
    deposition were developed. Concurrently, a vacuum system was designed and constructed,
    enabling optical measurements to be performed under a vacuum environment. Finally, in-situ
    vacuum-sealing of the optical cavities was attempted by deposition of various ‘sealing’ layers
    such as parylene deposition, sputtering of Si/SiO2, and plasma enhance chemical vapor
    deposition (PECVD) of SiO2. While these attempts were not entirely successful, they did provide
    an important basis for future work. The fabricated optical cavities exhibited a finesse of ~ 500 at
    1550 nm wavelength range. Furthermore, mechanical vibrational modes were observed with
    mechanical quality factor ~200 for fundamental resonant frequencies in the ~ 5MHz-15MHz
    range for different devices.
    For the elliptical cavities, buckled domes with a large difference in radius of curvature
    along the major and minor axis were realized through appropriate patterning of a low-adhesion

    layer. These birefringent optical cavities exhibit astigmatism (two nested sets of Hermite-
    Gaussian modes reflecting the two radii of curvature) and birefringence (slightly non-degenerate


    resonant wavelengths for polarization along the major and minor axes of the ellipse). The

    observed astigmatism and birefringence are in good agreement with the predictions of a vector-
    modified paraxial wave theory. The cavities exhibited finesse of ~ 250 at 1550 nm wavelength

    range and polarization-mode splitting of the fundamental mode by ~25 GHz.

  • Subjects / Keywords
  • Graduation date
    Fall 2022
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Library 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.