Chiral interactions of Quantum Dots embedded within Nanophotonic Waveguides

This thesis describes the couplings and interactions of quantum dots embedded within nanoscale photonic waveguides. Optical spectroscopic measurements were performed on these devices for the development of integrated quantum optical circuits using III-V semiconductors and self-assembled quantum dots.
Due to the confinement of electromagnetic radiation in photonic structures, it is possible to have a longitudinal component of the electric field within a waveguide, opposed to only a transverse component. This means that the electric field experienced by an emitter varies depending on the position of the emitter within the waveguide. In the symmetric case emission rates are equal along each arm of the waveguide. For a non-symmetric case (a chiral case) the emission for a QD exciton transition is not equal along both waveguide arms. In the most extreme case unidirectinal emission arises.
Using this, a method of directly reading out the spin state of an emitter via
spin to path conversion is achieved. By injecting quasi-resonant light into one side of the QD-waveguide system, determining the propagation direction, it is possible to selectively excite QD exciton transitions. This path to spin conversion breaks the reciprocity of the system, as light travelling the opposite direction will only interact
with the orthogonal QD component. The subsequent re-emission is also directional. Resonant transmission and reflection measurments are performed on a chirally coupled QD in a waveguide geometry. Dips in the transmission and peaks in the reflection spectra are observed. The chiral interface causes an asymmetry to be observed in transmission for opposite helicity QD exciton components. An asymmetry is also observed in reflection, which is unexpected, but is explained by use of a numerical model which reveals the effect
is due to partial saturation of the more strongly coupled QD exciton component.