Fabrication of Tapered Optical Fibers for Free-Space Access Microcavities

Progress in cavity quantum electrodynamics based platforms for quantum networks is reliant on the development of easily accessible microcavities with high-cooperativity and flexible designs. To realize efficient scalable quantum information settings and to enable couplings of multiple atomic qubits, the cavities employed should be fiber-coupled and should enable a low-noise environment, while facilitating maximal optical access to the atoms trapped in the center. To this end, this thesis explores methods for the development of tapered optical fibers suitable for integrated cavity designs with optimal free-space access. The tapered fibers explored in this work are fabricated with a chemical etching procedure employing the vapor phase of hydrofluoric acid (HF). The tapering process is anteceded with the curing of a photosensitive polymer at the tip of the fiber, aiming to preserve the integrity of the fiber during the etching process by creating an HF-resistant protective cap. The conducted experiments show, that although the fabricated protective coatings are not attacked during the etching, they do not demonstrate sufficient protective properties. Further, it is concluded that the HF vapor phase can successfully lead to the formation of tapered fiber profiles, albeit in a non-reproducible manner. As a result, the promising but not consistently reproducible experimental findings highlight the need for an enhanced control over several variables in order to fine-tune and optimize the etching process.