Two aspects were investigated in parallel: the enhancement from dielectric nanoantennae and optical properties from emitters, the ultimate goal being to combine these two aspects.
During a secondment at the University of Sheffield, I could learn how to perform microphotoluminescence measurements on WSe2 covered WS2 nanoantenna arrays. However, after several tests, we decided to focus on a different high-index material, gallium phosphide (GaP) which is also much simpler to fabricate.
Infinity-shaped GaP nanoantennae were fabricated from a topologically optimised design investigated theoretically in the group. Nanofabrication was undergone in collaboration with LMU Munich, Germany and their enhancement was measured during a secondment at the Fresnel Institute, Marseille, France using fluorescence correlation spectroscopy. This technique is very challenging as it relies on the measurement of the brightness from single molecules in the nanogap’s volume over time. We successfully measured the enhancement of individual nanoantennae according to their gap size with an enhancement factor of up to 100-fold. The interest lies in the fact that nanogaps enhancement can be used to place emitters in their centre. This work has been presented at the CLEO Europe/EQEC conference in Munich and was submitted to a peer-reviewed journal for publication.
The characterisation of emitters involved single photon measurements from giant quantum dots deterministically positioned in an array, thanks to a collaborative effort with IIT Genoa, Italy (positioning) and University of Ghent, Belgium (fabrication). We showed that the quantum dots retain their quantum optical properties after being processed for placement and that the arrays show a Poisson distribution of single emitters, i.e. best achievable results with a stochastic technique. These results were published in: ACS Photonics 2023, 10, 1662–1670.
The next goal is to use this positioning technique to place quantum dots deterministically in nanogaps from an array of infinity-shaped GaP nanoantennae and measure the enhanced single photon emission.
Exploitation and dissemination of results was undertaken as follow:
- Publication in ACS Photonics 2023, 10, 1662–1670 and a soon to be published paper with an arXiv preprint 2310.07309.
- Outreach activities at the International Day of Lights 2022 (Guiding Lights glass art sculpture), Imperial Lates in November 2022 (Nanolights), Great Exhibition Road Festival 2023 (Tiny Lights at your Fingertips)
- International conference CLEO Europe/EQEC 2023 talk "Performance of GaP nanoantennas from optimised design"
