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Permanent link (DOI): https://doi.org/10.7939/R3V62F
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Air-core microcavities and metal-dielectric filters - building blocks for optofluidic microsystems Open Access
- Other title
Optical admittance matching
Air-core optical cavities
- Type of item
- Degree grantor
University of Alberta
- Author or creator
Allen, Trevor W.
- Supervisor and department
DeCorby, Ray (Electrical and Computer Engineering)
- Examining committee member and department
Meldrum, Al (Physics)
Fair, Ivan (Electrical and Computer Engineering)
Jacob, Zubin (Electrical and Computer Engineering)
Tsui, Ying (Electrical and Computer Engineering)
Janz, Siegfried (Carleton University, Ottawa)
Department of Electrical and Computer Engineering
Photonics and Plasmas
- Date accepted
- Graduation date
Doctor of Philosophy
- Degree level
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.
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
- Citation for previous publication
T.W. Allen, J. Silverstone, N. Ponnampalam, T. Olsen, A. Meldrum, R.G. DeCorby, "High-finesse cavities fabricated by buckling self-assembly of a-Si/SiO2 multilayers", Opt. Express, vol. 19, pp. 18903-18909, 2011.T.W. Allen, R.G. DeCorby, "Assessing the maximum transmittance of periodic metal-dielectric multilayers", J. Opt. Soc. Am. B, vol. 28, pp. 2529-2536, 2011.T.W.Allen, R.G. DeCorby, "Conditions for admittance-matched tunneling through symmetric metal-dielectric stacks", Opt. Express, vol. 20, pp. A578-A588, 2012.
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