PhD defence, by Yueguang Zhou

Abstract

The development of advanced single-photon sources is essential for driving progress in integrated photonic quantum systems, which have the potential to transform computing, communication, and sensing technologies. The III-V semiconductor quantum dot is a standout candidate in this field, advantageous for its deterministic, efficient, and high-quality single-photon emissions.

This research explores a new and promising material platform for quantum dots called GaAs-on-insulator (GaAsOI). This platform stands out because it features a high-index contrast that significantly enhances the efficiency of coupling photons from the quantum dot into an optical waveguide.

The study involves both theoretical and experimental work on GaAsOI quantum dot (QD) single-photon sources. Theoretically, it introduces two innovative nanophotonic structures—the V-groove waveguide and the bowtie circular Bragg grating cavity structure, which show significant promise, as evidenced by their high Purcell factors and coupling efficiency. Experimentally, the thesis outlines the fabrication processes and various cavity designs on the GaAsOI platform, such as the microring, nanobeam, and fishbone cavities, which are highlighted for their ability to emit pure single photons associated with high Purcell factors.

Beyond generating single photons, the GaAsOI platform's versatility supports a range of functional photonic devices, including lasers, modulators, and integrated quantum circuits for composing a complete quantum information processing system, which positions GaAsOI as a compelling platform for future integrated photonic quantum technologies.

Supervisors

• Principal supervisor: Senior Researcher Minhao Pu, DTU Electro, Denmark
• Co-supervisor: Professor Niels Gregersen, DTU Electro, Denmark
• Co-supervisor: Professor Kresten Yvind, DTU Electro, Denmark

Assessment committee

• Senior Researcher Yunhong Ding, DTU Electro, Denmark
• Associate Professor Leonardo Midolo, University of Copenhagen, Denmark
• Professor Armando Rastelli, Johannes Kepler University of Linz, Austria

Master of the Ceremony

• Senior Researcher Battulga Munkhbat, Department of Electrical and Photonics Engineering, DTU, Denmark