Excitonic 2D Metasurfaces for Active Multifunctional Flat Optics

Project Information

ExMAM

Grant agreement ID: 101116984

DOI

10.3030/101116984

EC signature date 18 September 2023

Start date 1 January 2024

End date 31 December 2028

Funded under

• European Research Council (ERC)

Total cost

€ 1 499 985,00

EU contribution

€ 1 499 985,00

Coordinated by

UNIVERSITEIT VAN AMSTERDAM
Netherlands

Periodic Reporting for period 1 - ExMAM (Excitonic 2D Metasurfaces for Active Multifunctional Flat Optics)

Reporting period: 2024-01-01 to 2026-06-30

Summary of the context and overall objectives of the project

Optical elements, like lenses, filters and prisms are commonly used to steer and manipulate light. However, their bulky and heavy form puts major limitations on their applicability in novel applications where size and weight are crucial, including wearable devices, optical communications, and satelites. Building on the advent of nanotechnology, new optical coatings have been developed that perform identical and even more complex optical functions using ultra-thin and light-weight nanostructured optical coatings. Such “metasurfaces” are already revolutinizing the photonics industry, yet a crucial challenge remains. After nanofabrication, the optical function of metasurfaces is fixed, defined by the nanoscale geometry of the constitutent building blocks. At the same time, new applications demand active and dynamic optical elements where the multiple optical functions can be combined in a single design, and their function can be tuned electronically.

In ExMAM we combine these metasurfaces with novel 2D quantum materials that exhibit the remarkable property that their refractive index can be tuned electrostatically. By combining their complementary strengths, we will: (i) study the electrically-tunabale light-matter interaction; (ii) achieve highly efficient tunable metasurfaces; (iii) stack these surfaces to combine them into multifunctional flat optics. The results of this project will offer new insights into the physics of light-matter interaction of quantum materials, as well as enable new optoelectronic devices.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Throughout the first stage of the project, we have:
1- developed a new technique to “stamp” large-area 2D monolayers, that are just 1 layer of atoms thick, onto arbitrary substrates and devices without deteriorating their material properties. This is crucial since it is the first step towards integrating 2D monolayers with metasurfaces.
2- demonstrated that the monolayer material itself can also function as the metasurface by directly patterning the monolayer into a metasurface. Using this we showed that light can be confined in exciton-polariton states in such atomically thin layers.
3- we formulated a mathematical model for light scattering by monolayer nanostructures. Using this model we derived the fundamental limits of such light scattering, providing rational guidelines for the design of high-efficiency excitonic metasurfaces.
4- using numerical simulations, we studied how heterostructure 2D materials combined with a judiciously engineered metasurface on its surface can be used to achieve full 2-pi phase modulation without any cross talk in the amplitude of the signal.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

In the second stage of the project, we will capitalize on the foundational work of the first stage and work towards fully functional electrically-tunable optical elements. Crucially, our ability to assemble 2D materials into nanopatterned coatings offers the ability to realize multifunctional elements that exhibit high efficiencies. Vice versa, the excitonic metasurfaces will offer a unique ability to study the underying solid-state physics with a high sensitivity. Altogether, these results will impact the fields of both optical metasurfaces, solid-state physics, and 2D material science.