QLab Cardiff

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Well done to Sam on leading this work we have just published in ACS Photonics. In the paper we show a new technique to pinpoint the location of quantum emitters within a few nanometers, at a resolution much below the expected ~ wavelength scale resolution of the optical system. Through repeated measurements which are cross referenced to markers on the sample surface, we can then etch away semiconductor around the emitter to create an optical resonator. This leads to enhanced photon collection and preserves the quantum nature of the emitted light. I have high hopes this technique can be used for many of our future experiments and inspire similar work in other materials.

We have a new paper out in APL Photonics. Working with Cambridge University’s Centre for Gallium Nitride, we have shown for the first time, how to grow this technologically important semiconductor with quantum emitters at a controlled depth. Previously, it was known that these emitters form in the first stages of growth, which always leaves them at the bottom of the crystal layer. Using the process described in the paper, we can grow the emitters at arbitrary depth which is essential for future applications of these emitters in useful devices. As Gallium Nitride is a favoured material for LED lighting and high-power electronics, there are lots of device designs we can now explore that build on this breakthrough.

I was on a panel discussion at Wales Tech Week yesterday in the international conference centre. Discussion quantum technology with Anke Lohmann of Anchored in, Zoe Davison of BT, Iwan Davies from IQE and Paul Ceely from the Digital Catapult.

It was a great pleasure for us to host the annual ‘Quantum Dot Day’ in Cardiff University this year. The meeting topic was expanded to include many site-controlled quantum emitters in different materials such as diamond, GaN, hBN as well as our old friends the quantum dots. We had a great turnout, many cutting-edge and informative talks, excellent posters and industry support from Laser2000, PI-KEM, Toptica,Lambda Photometrics, Quantum Design, the Institute for Compound Semiconductors and the Institute of Physics. Special thanks to our invited speakers Prof Christian Bonato, Dr Elisa Sala, Dr Charlotte Ovenden and Dr Aymeric Delteil.

We’re pleased to announce the publication of our latest paper on the properties of microcavity quantum light sources. Our study reveals that the complex electromagnetic environment of these highly efficient sources is strongly influenced by the emission wavelength—a finding that deepens our understanding of how to optimize their performance. By comparing the full microcavity structure to a simplified model in which the quantum light source is embedded in a uniform material, we discovered that the shape of the cavity edges plays a crucial role in determining efficiency. Congratulations to Matthew Jordan for leading this research, and sincere thanks to Professor Wolfgang Langbein for co-supervision and many valuable insights.

$New paper: we employ femtosecond laser writing to create nanoablations with sub-diffraction-limited diameter and use rapid thermal annealing to activate co-located stable emitters. The emitters show a MHz antibunched emission with a sharp spectral peak at room temperature. Our study not only presents an efficient approach to laser-written nanofabrication on GaN but also offers a promising pathway for the deterministic creation of quantum emitters in GaN.$

Welcome to Jacob and Harry, who joined the group recently as PhD student and PDRA, respectively. We are looking forward to some great results in the next few years.

I am in Shanghai at the 33rd International Conference on Defects in Semiconductors at Fudan University, presenting the group's work on colour centers in wide-bandgap semiconductors. Definitely one of the most interesting places I have been.

Congratulations to Drs Rachel Clark, @josephcannon_ , @mathew_ann_ and Matthew Jordan who all graduated from their Cardiff University PhDs this week. Special thanks must go to co-supervisors Ian Farrer, Sang Soon Oh, Wolfgang Langbein, David Wallis for their support and the rest of the group including Sam Bishop and JP Hadden their essential contributions over the last years. Wishing you lots of success in your future careers!