Pillar-array based optical cavities have unique properties, e.g., having a large and connected low dielectric index space (normally air space), exhibiting a large band gap for transverse magnetic modes, having a large percent of electric field energy in air and standing on a substrate. These properties make them well suitable for applications such as optical sensing and terahertz quantum cascade lasers. However there has been rare research in it due to the common belief that pillar arrays have excessive leakage to the substrate. With careful design, we provided several methods to reduce such a leakage and experimentally proved a high quality factor (Q) pillar-array based cavity is practical. We also explored the usage of such a cavity for optical sensing.
Numerical methods such as finite-difference time-domain and plane-wave expansion were used in the design of the cavity. Then in microwave spectrum, cavities consisting of
dielectric rods were used to test the validity of the theory. Additionally, we observed that a high-Q cavity for modes above light line is feasible and it is very suitable to measure the optical absorption of materials introduce inside the mode volume. Finally in the optical domain, pillar arrays were fabricated in Si/SiO2 material system and measured. Q as high as 27,600 was shown and when applying accurate refractive indices, for every delta n = 0.01, the peak wavelength shifted as large as 3.5 nm, testifying the ultra sensitivity
of the cavity to the environmental dielectric change.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/26263 |
| Date | 17 February 2011 |
| Creators | Xu, Alan Tao |
| Contributors | Ruda, Harry E. |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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