On-chip single-photon sources for quantum information technology

The interaction of light with matter is of fundamental importance, and is the mechanism that governs how photons are generated and used. Control over this interaction can be achieved by using an optical cavity, engineering the properties of the material to create a photonic crystal, or by using plasmonic devices to confine the electromagnetic field locally. Emitters can be coupled to devices with high-quality light confinement to enhance the emission rates, creating brighter light sources for detection, for contaminant sensing or for quantum information technologies. Such technologies require bright and pure-single photon sources: a solid-state platform can meet these requirements whilst also being compatible with well-developed fabrication technologies and long-term stability. We report metallic nanorings fabricated around selected solid-state quantum dots, to enhance vertical emission for collection by free-space optics, using a nanometre-accurate positioning technique. Enhancements of a single emission line as high as x25 are recorded thanks to a broadband lensing effect. Such metallic nanorings can be combined with deterministically-deposited super-solid immersion lenses, to provide further enhancement, x10, to that of the nanoring-creating photon sources with up to 1MHz emission rates. The light-matter interaction can be modified by using photonic crystals. The performance of photonic crystal devices in the visible light regime is hampered by unavoidable fabrication imperfections, which affect devices on the length scales required for visible light operation. An alternative to such highly engineered devices is to use the fabrication disorder as a resource. Anderson localization is demonstrated using photonic crystal waveguides, and directly imaged for the first time in the visible on a nanophotonic chip. Spectral analysis shows Q-factors approaching 10,000, exceeding highly engineered devices for the first time. Optical sensing is demonstrated by making use of high-quality resonances from photonic crystals to perform sensing: a contaminant was introduced, and a resonance was shown to red-shift over x100 its line-width in response. The resonances are also sensitive to temperature, shifting about 2nm under a 290K change. An alternative localization mechanism is to use aperiodic structures, where a quasi-random pattern is procedurally generated. We have fabricated and optically characterised aperiodic structures, showing efficient light confinement in a 2D system.