Optimising mode-matching between quantum dot micropillars and single mode fibres using micro-lenses

A deterministic single photon source is a vital missing ingredient from the quantum technology supply chain. These are sources that exploit single quantum emitters to realise a "push button" single photon source (SPS). Quantum dots (QDs) in III-V semiconductor are some of the brightest quantum emitters available. Their semiconductor nature means that it is straight forwards to incorporate them into
photonic structures such that output photons can be funnelled into a desired spatial mode. Vertically emitting structures such as micropillars have been particularly successful and we have reached the point where single photons produced from such sources have a 60% chance of being collected and detected. Most of the existing loss is present in the bulk optics that is used to couple light to and from the QD based devices. The grand challenge is to remove the need for bulk optics and create a highly efficient, user friendly, packaged SPS that is directly coupled to a single mode optical fibre. For this we need to control the output emission from our QD based single photon source to make it compatible with standard fibre optics. This PhD will investigate the addition of a micro-lens layer to the QD SPS to achieve optimal mode-matching between the source and the fibre. This will involve simulation and design, fabrication as well as testing and validation. The goal will be to have prototype devices and the echnological know-how to build a packaged single photon source. This important technology would be applicable to a wide range of solid-state quantum emitters, could be licenced or spun out to fill a vital gap in the quantum technology supply chain.