Simulation and Design of Microstructured Optical Fibers with Optimized Purcell Factor

This thesis addresses the challenges associated with the integration of quantum dot (QD) single-photon sources into optical fibers for quantum communication. Quantum computing relies on the secure quantum key distribution (QKD), which necessitates high-efficiency single-photon sources. Current QD sources based on epitaxially grown QDs encounter significant obstacles in photon collection efficiency, suffering from misalignment of the collection microoptics. This hinders integration within the existing global optical fiber network. This thesis explores a new approach for the integration of QDs into fiber structures, including solution-processed colloidal QDs fibers with a nanobore and tapered fibers. Numerical simulations, conducted using finite-difference time-domain (FDTD) simulations, analyze the effects of fiber radius, dipole position, and orientation on both the Purcell factor and fundamental mode power, thus identifying critical factors that govern photon emission and collection efficiency. Furthermore, this study utilizes topology optimization to enhance fiber designs for improved light capture from QDs, achieving increased Purcell factors through precise modifications of the fiber geometry. The findings show that up to 104% of the photons radiated by a QD in the homogeneous medium air, regardless of its orientation on the cross-section within an air-filled nanobore, can be captured in the fundamental mode of a tapered silica fiber. This highlights the potential for QD integration in nanobore fibers, although further research is necessary to develop a viable production process for such fiber designs.