Polarisation engineering of nanophotonic structures containing quantum emitters

In this thesis I will investigate photonic structures that can be utilised to entangle the electron spin of a self-assembled quantum dot with a photon. Charged. quantum dots, whose emitted photons are trapped or guided by the photonic structure, can be utilised as quantum memories and form the basic building block of the interface. It will be shown, using a dyadic Green's function method, that photonic structures need to fulfil! two criteria in order to implement a spin-to-photon interface. Criterion one is the support of a degenerate mode, criterion two requires the quantum dot to couple equally to the two orthogonal modes. Only a subset of photonic structures fulfill these requirements. Two structures that fulfill these criteria are investigated in more detail using the dyadic Green's function method developed, and I show that both structures enable in-plane spin readout, which had not been demonstrated yet. The first, a cross configuration of two nanowire waveguides, couples a spin state to different waveguides of the cross configuration. By recombining two of the four arms and interfering the outputs spin readout is made possible. It will be shown that the device has two working regimes for spin readout depending on the quantum dot position. The structure works well in both regimes. The second structure, a photonic crystal waveguide, enables in-plane spin readout by positioning the quantum dot on a circular polarisation singularity resulting in directional coupling of different spin states. Subsequently, I will show that this structure is able to generate spin-photon and photon-photon entanglement by reflecting photons of the waveguide.EThOS - Electronic Theses Online ServiceGBUnited Kingdo