Optoelectronic and photonic control of single quantum dots

Abstract

The area of quantum information promises to deliver a range of new technologies in the fields of quantum computing and quantum communication. Devices based on semiconductor quantum dots hold great potential for the practical realisation of many of the components required in the proposed schemes. This thesis describes the development of several quantum dot devices. By integrating a quantum dot into a p-i-n diode, it was possible to control the dominant emission lines in its photoluminescence spectrum and to maximise the degree of polarisation correlation between the two photons emitted in the biexciton decay. With the same device under a magnetic field, a digital memory was demonstrated. The polarisation information of a single photon was stored as the spin of an electron inside the quantum dot, and was deterministically recovered some time later by the application of an electrical trigger. A fabrication process was developed in order to produce high quality two dimensional slab photonic crystals operating with a photonic band gap at ~ 900 nm. By placing a quantum dot into an appropriately designed H1 photonic crystal cavity, strong coupling was achieved between the dot and the monopole mode of the cavity. The vacuum Rabi splitting was found to be constant for all linear polarisations due to the unpolarised nature of the far-field of the mode. Finally, a new kind of cavity based on photonic crystal waveguides was developed. A Purcell enhancement of the in-plane spontaneous emission from a quantum dot coupled to a unidirectional photonic crystal waveguide was demonstrated.