Design, fabrication and characterization of diamond-based photonic microcavities.

摘要

Negatively charged nitrogen-vacancy (N-V) centers in diamond have many unique properties, such as very long spin lifetimes and excellent suitability for single photon sources at room temperature. When such sources are matched by the formation of high quality cavities, opportunities arise for enhancement of spontaneous emission rates and spin coherence times associated with N-V centers. The challenges of fabricating such high quality cavities in diamond are formidable; this thesis develops the fabrication and characterization of nanocrystalline diamond microdisk and photonic crystal cavities. The quality factors (Qs) of the microdisk Whispering Gallery Modes were about 100. Analysis through focus ion beam milling, micro-photoluminescence and tapered fiber measurement indicates the limitation of the Qs is the scattering and/or absorption loss associated with granular structure of the materials. Fundamental modes were observed for the nanocrystalline diamond photonic crystal cavities, with Qs as high as 585. Polarization measurements show that the scattering loss through the grain boundaries and the rough surfaces is the main limitation of high quality photonic cavities in nanocrystalline materials. Fabricating such microcavities in single crystal diamond encounters further challenges.; The challenge in the case of single crystal diamond is the formation of the suspended structure. Combining low energy ion implantation, homo-epitaxial diamond growth, and electrochemical etching with local electrodes, we fabricated microdisk structures and suspended cantilevers in single crystal diamond. Further improvements in the process are required to form photonic devices that are truly isolated from the substrate.