Master Thesis Defense: Hanna Krystyna Salamon

Novel nanophotonic interface for droplet GaAs quantum dots

GaAs quantum dots (QDs) are nanostructures embedded in a AlGaAs host material which can be fabricated via droplet epitaxy. A low Al concentration of the host material is a critical requirement for the quality of GaAs QDs as a single photon source (SPS) for quantum optics and photonic devices for scalable quantum networks. However, the reduction of the Al concentration has a been a challenge limiting the quality and thereby the potential of GaAs as SPSs for photonic quantum devices.

Recently, advancements in the fabrication of droplet GaAs QDs allowed for a drastic reduction of the Al concentration and thus introducing a novel generation of QDs. Droplet GaAs QDs have proven to be (i) reliable in fabrication, (ii) SPSs of outstanding quality, and (iii) are emitting in the spectral range of the Rubidium D-1 and D-2 lines. This new generation of GaAs droplet QDs thus promises to leverage the progress towards large scale production of photonic devices for scalable quantum networks. In particular, the compatibility with rubidium based quantum memories allows for quantum information processing applications. 

The main goal of the project is to design and characterize photonic circuits based on the new generation GaAs droplet QDs as embedded SPSs. More specially, the target is to realize light-matter interfaces of GaAs droplet QDs and nanophotonic waveguides. The nanophotonic waveguides will be tailored to enhance and modify light-matter interfaces for deterministic coupling, high purity and bright single photon emission. DC-stark tuning and charge tuning will be demonstrated by embedding the nanophotonic devices in a n-i-p diode. The properties of the light-matter interface will be investigated experimentally using high-resolution and time-resolved optical spectroscopy. Specifically, the purity and the efficiency of the SPS will be determined.