Ultrafast quantum light sources based on defect centres in 2D materials

The studentship is part of the UK’s Centre of Doctoral Training in Metamaterials (XM2) based in the Departments of Physics and Engineering on the Streatham Campus in Exeter. Its aim is to undertake world-leading research, while training scientists and engineers with the relevant research skills and knowledge, and professional attributes for industry and academia.

The widespread application of quantum photonic technologies is hindered by the availability of high performance single and indistinguishable photon sources; yet the potential to revolutionise communication, measurement and computing demands that new systems and approaches are investigated. One such emerging system is defect emitters in few atomic layer crystals. Thanks to the ease with which 2D materials can be manipulated, there is the unique capacity to integrate them with high performance nanophotonic devices. In particular, defect emitters in hexagonal boron nitride (hBN) have recently emerged as robust quantum emitters with bright, stable fluorescence and nanosecond radiative lifetimes at room temperature [1], but this potential is tempered by a lack of fundamental understanding of the emitter structure and how it interacts with its local environment.

The first objective of the project will be to address this issue and study the dominant dephasing processes arising from the interaction of the two-level quantum system with lattice phonons and charge fluctuations. This will be achieved though the integration of few layer hBN crystals with high quality silicon nitride based integrated photonics. This will enable various spectroscopic measurements and will also stabilise local charge fluctuations through encapsulation of the emitters. Combined with temperature dependent investigations, this will allow a systematic investigation of the dominant dephasing mechanisms and give a true picture of the potential for quantum optics.

The second major objective of this work will be the integration of defect emitters in 2D materials with hybrid plasmonic-dielectric nanophotonics. Although the radiative lifetime of most quantum emitters is on the order of nanoseconds [2], this still limits the photon emission rate to 1000 can be realised with realistic device parameters [3], thereby enabling single photon rates of 10s or even 100s GHz along with vastly improved timing jitter.

[1] Tran et al., Nature Nanotechnology, 11, 37 (2016).
[2] Aharonovich et al., Nature Photonics 10, 361 (2016).
[3] Doeleman et al., ACS Photonics 3, 1943 (2016).