Stratified Fiber-Resonator: Fabrication, Characterization and Potential Applications
1 online resource (160 pages) : PDF
University of North Carolina at Charlotte
Whispering Gallery Mode Resonators (WGMR) are compact, monolithic resonators used for photonic applications. Controlling the properties of WGM while keeping the geometry simple is desired to improve their performance, especially for sensing and non-linear interactions. One way to achieve this is by coating the WGMR with a layer of certain refractive index profile, which has been shown to modify the effective optical potential thus allowing control of the WGM field. This dissertation focusses on coating of an optical fiber with single or multiple thin films with precise control of thickness and refractive index. Transfer matrix method is applied to study the effect of coated films on the mode structures and field profiles of fiber WGM. For small layer thickness the mode shifts to the periphery while for large thicknesses waveguide modes are found and coupling is observed for multiple layers. Fibers are coated uniformly in a commercial PECVD instrument modified to enable continuous rotation of fibers. Mie scattering of coated fibers is utilized to extract refractive index and thickness of coated thin films, which is otherwise challenging due to non-flat topology and small size of the fibers. It is found that rotation leads to higher deposition rate and refractive index of films, compared to those deposited on a static wafer. These differences are demonstrated to depend on the rotation speed, opening interesting dynamic tuning capabilities. Further, fibers with Bragg layers are fabricated and their scattering analyzed. It is found that judicious choice of film thickness can drastically modify scattering signatures of Bragg fibers. A ray model taking into account photonic bandgap of Bragg layers is proposed to successfully explain these anomalous features.
Optical Science & Engineering
Farahi, FaramarzGbur, GregEgusa, ShunjiSmith, Stuart
Thesis (Ph.D.)--University of North Carolina at Charlotte, 2017.
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