Broadband Micropillar Resonators with Solid State Quantum Dots as Mass-Manufacturable Near-Ideal Single Photon Sources

Abstract

This thesis is an investigation of quantum dots in broadband micropillars for the design of high performance single photon sources. The careful analysis of the resonator structure and its properties allows for the development of a simple design recipe for devices which overcome previous limitations on highly efficient yet readily mass-manufacturable low Q devices. This thesis uses finite difference-time domain simulations to extend our understanding of quantum dots in dielectric resonators with finite lateral dimension by providing a novel understanding of the full 3 dimensional solution of micropillar cavities. We will show that that the often overlooked Purcell suppression of leaky decay can be used to elevate the performance of such devices beyond the theoretical limits of atom-cavity models, removing the need for high Purcell enhancement and narrow cavities to achieve ultra-high efficiency. Particular designs of highly efficient (> 90%) devices at low Q factors will be shown. The benefits of remaining in the high bandwidth regime will be quantified with theoretical modelling of the indistinguishability, purity, and fabricability advantages over narrowband resonators. Simultaneously high figures of merit for the proposed designs will be demonstrated, and we will touch upon the improved scalability of broadband micropillars over high Q devices used in the state of the art. Finally, experimental measurements of the photoluminescence of cavities and two different types of InAs quantum dots will be shown: InGaAs capped and bilayer quantum dots. The fabrication tolerances some cavity properties will be analysed, while polarisation resolved spectroscopy and power series measurements will be used to identify the observed states of each sample. Finally, a novel strategy for automated analysis using statistical methods will be shown which could significantly improve the time and cost to characterise a large set of devices using only a small sample.

Date of Award	17 Jun 2025
Original language	English
Awarding Institution	University of Bristol
Supervisor	Ruth Oulton (Supervisor) & Edmund G H Harbord (Supervisor)