Air-core microcavities and metal-dielectric filters - building blocks for optofluidic microsystems

  • Author / Creator
    Allen, Trevor W.
  • This thesis describes a study on two optical devices intended to be building blocks for the creation of integrated optical/microfluidic lab-on-a-chip systems. First, arrays of curved-mirror dome-shaped microcavities were fabricated by buckling self-assembly of a-Si/SiO2 multilayers. This novel technique employs controlled, stress-induced film delamination to form highly symmetric cavities with minimal roughness defects or geometrical imperfections. Measured cavity heights were in good agreement with predictions from elastic buckling theory. Also, the measured finesse (> 10^3) and quality factor (> 10^4 in the 1550-nm range) were close to reflectance-limited predictions, indicating low defects and roughness. Hermite- and Laguerre-Gaussian modes were observable, indicating a high degree of cylindrical symmetry. In the second part of the research, transmittance in periodic metal-dielectric multilayer structures was studied. Metal-dielectric stacks have many potential applications in optofluidic microsystems, including as transmission filters, superlenses, and substrates for surface plasmon sensors. In this work, we showed that potential transmittance theory provides a good method for describing the tunneling of photons through metal-dielectric stacks, for both Fabry-Perot and surface plasmon resonances. This approach explains the well-known fact that for a given thickness of metal, subdividing the metal into several thin films can increase the maximum transmittance. Conditions for admittance matching of dielectric-metal-dielectric unit cells to an external air medium were explored for Fabry-Perot based tunneling, revealing that thicker metal films require higher-index dielectrics for optimal admittance matching. It was also shown for the first time that potential transmittance theory can be used to predict the maximum possible transmittance in surface-plasmon-mediated tunneling. In a subsequent study, potential transmittance was used to derive an expression for reflection-less tunneling through a dielectric-metal-dielectric unit cell. For normal-incidence light in air, only a specific and impractically large dielectric index can enable a perfect admittance match. For off-normal incidence of TE-polarized light, an admittance match is obtained for a specific angle determined by the index of the ambient and dielectric media and the thickness and index of the metal. For TM-polarized light, admittance matching is possible for surface-plasmon-mediated tunneling. These results provide important insight for the design and optimization of optical filters and superlenses.

  • Subjects / Keywords
  • Graduation date
    Fall 2012
  • Type of Item
  • Degree
    Doctor of Philosophy
  • 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
  • Specialization
    • Photonics and Plasmas
  • Supervisor / co-supervisor and their department(s)
  • Examining committee members and their departments
    • Jacob, Zubin (Electrical and Computer Engineering)
    • Fair, Ivan (Electrical and Computer Engineering)
    • Tsui, Ying (Electrical and Computer Engineering)
    • Meldrum, Al (Physics)
    • Janz, Siegfried (Carleton University, Ottawa)