Master Thesis Defense: Christian Hjort Christiansen

Self-Assembled InAs Quantum Dot Molecules in Photonic Waveguides

This thesis examines quantum dot molecules (QDMs) consisting of two self-assembled InAs quantum dots (QDs) grown vertically, separated by a tunneling barrier, and embedded in a photonic waveguide. Potential transduction schemes leveraging the large permanent electric dipole moment and anti-crossings of QDMs, are examined. A transduction efficiency of up to unity is theorized, demanding QDM anti-crossings to be resonant with the transduced microwave photon, thus motivating the simulation and characterization of QDMs.

In this thesis, anti-crossings of just below 400 GHz and very large DC Stark tuning of several hundred GHz per kV/cm are measured. The decay rates of these excitons are observed to change by up to a factor of 7.9±0.6, depending on the applied electric field. By resonant transmission measurements, permanent electric dipole moments of direct excitons, which point in the opposite direction to those of single QDs, are measured, and attributed as a consequence of QDM coupling. For future designs, larger tunneling barriers are suggested to decrease the tunnel coupling and thus the anti-crossing, while increasing the permanent electric dipole moment.