Periodic Reporting for period 1 - BrightNano-vdW (Nanostructured van der Waals materials for enhanced light emission)
Reporting period: 2020-10-05 to 2023-10-04
The purpose of this Individual Fellowship was to explore the properties of high index dielectrics, in particular van Der Waals (vdW) materials, in order to use them as platforms for highly efficient single-photon and nonlinear light sources with potential implementation in photonic-based devices.
The main idea was to use nanostructures to improve the emission efficiency of high-index materials. Indeed, nanogaps and nanocavities are useful resonators which increase the rate of light extraction from a nearby emitter. The challenges of such approach requires are on one hand, the precise positioning of single emitters at the nanoscale and on the other, optimised nanostructuring of materials to provide large signal enhancement. With these goals in mind, vdW materials were considered as both emitters and nanostructures, thanks to their low losses and high refractive indices.
The main success of the fellowship were to fabricate nanostructures from lossless dielectric materials which were topologically optimised for photoluminescence enhancement and to show deterministic positioning of single photon emitters.
The main idea was to use nanostructures to improve the emission efficiency of high-index materials. Indeed, nanogaps and nanocavities are useful resonators which increase the rate of light extraction from a nearby emitter. The challenges of such approach requires are on one hand, the precise positioning of single emitters at the nanoscale and on the other, optimised nanostructuring of materials to provide large signal enhancement. With these goals in mind, vdW materials were considered as both emitters and nanostructures, thanks to their low losses and high refractive indices.
The main success of the fellowship were to fabricate nanostructures from lossless dielectric materials which were topologically optimised for photoluminescence enhancement and to show deterministic positioning of single photon emitters.
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"
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"
The next step is to use this positioning technique to deterministically place quantum dots in an array of nanogaps, such as the ones made of infinity-shaped GaP nanoantennae, and determine the enhanced single photon response. To solve the challenge of positioning, we carry out photolithography of 2D and 3D nanostructures arrays based on an array of quantum dots to write upon and readily integrate within the structure.
The ultimate goal is to integrate these arrays to optoelectronic devices towards utilisation as room temperature bright on-chip sources for quantum technologies. This will allow for faster and more efficient devices and lead to less energy consuming full-photonic devices which can be implemented in integrated photonic devices.
Progress beyond the state of the art:
- Deterministic positioning of single photon emitters
- Low-loss, high-gain nanoantennas for enhanced emission rate of emitters
Scientific potential impact:
- On-chip implementation
- High resolution sensing
- Towards quantum devices
- Full photonic devices
The ultimate goal is to integrate these arrays to optoelectronic devices towards utilisation as room temperature bright on-chip sources for quantum technologies. This will allow for faster and more efficient devices and lead to less energy consuming full-photonic devices which can be implemented in integrated photonic devices.
Progress beyond the state of the art:
- Deterministic positioning of single photon emitters
- Low-loss, high-gain nanoantennas for enhanced emission rate of emitters
Scientific potential impact:
- On-chip implementation
- High resolution sensing
- Towards quantum devices
- Full photonic devices