Fiber-coupled ultra-high-Q microresonators for nonlinear and quantum optics

The ability to confine optical energy in small volumes for long periods of time is desirable for a number of applications, ranging from photonics and nonlinear optics, to fundamental studies in quantum electrodynamics. Whispering-gallery-mode microresonators are a promising cavity to study, due to the ability to obtain quality factors exceeding 100 million in micron-scale volumes. This thesis investigates the suitability of ultra-high-quality factor silica microresonators (both silica microspheres and silica toroidal microresonators) for nonlinear and quantum optics. Crucial to the actual use of these structures is the ability to efficiently excite and extract optical energy. The first part of this thesis investigates the ability to achieve near lossless coupling between a fiber-taper waveguide and a silica microresonator. It is shown that a coupling ideality (which is the fraction of energy coupled into the desired fiber mode) in excess of 99.97% is possible, meaning that optical energy can be coupled both to and from the optical resonator with near perfect efficiency.; Using tapered fibers, low threshold stimulated Raman scattering is observed in both silica microspheres and silica microtoroids at record low incident pump powers below 100 microwatts, much lower than previous devices. High conversion efficiencies (>35%) are also realized. Furthermore, the conditions for optimized performance of both stimulated Raman scattering and parametric oscillation in a microcavity are described.; Lastly, the suitability of toroidal microcavities for strong coupling cavity quantum electrodynamics is investigated. Numerical modeling of the optical modes demonstrates a significant reduction of modal volume with respect to spherical cavities, while retaining high quality factors. The extra degree of freedom of toroid microcavities can be used to achieve improved strong-coupling characteristics, and numerical results for atom-cavity coupling strength, critical atom number and critical photon numbers for cesium are calculated and shown to exceed values currently possible using Fabry-Perot cavities. Modeling predicts atom-cavity coupling rates exceeding 700 MHz and critical atom numbers approaching 10{lcub}-7{rcub}.