Atomically layered materials for next-generation metasurfaces

Project Information

METANEXT

Grant agreement ID: 101078018

DOI

10.3030/101078018

EC signature date 12 April 2023

Start date 1 May 2023

End date 30 April 2028

Funded under

• European Research Council (ERC)

Total cost

€ 1 498 056,00

EU contribution

€ 1 498 056,00

Coordinated by

LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN
Germany

Periodic Reporting for period 1 - METANEXT (Atomically layered materials for next-generation metasurfaces)

Reporting period: 2023-05-01 to 2025-10-31

Summary of the context and overall objectives of the project

Controlling light-matter interaction at the nanoscale is a cornerstone of modern science and technology. From optical communication to biomedical sensing, the ability to guide and manipulate underpins a wide range of applications. Two emerging fields have provided powerful tools in this context: metasurfaces, ultrathin, engineered interfaces that control light with subwavelength precision, and two-dimensional (2D) materials, which offer exceptional optical and electronic properties within atomically thin layers bound by van der Waals forces. While each field has seen rapid progress individually, integrating them into a single, scalable, high-performance optical system has remained a major challenge due to fundamental material and fabrication limitations.

The METANEXT project directly addresses this challenge by proposing a new class of optical platform: van der Waals heterostructure metasurfaces, where metasurfaces are constructed solely from carefully crafted 2D material stacks. This concept leverages the nanoscale design flexibility of metasurfaces and the atomically defined structure of 2D materials, enabling unprecedented control over light-matter interactions.

The expected impact of METANEXT is the realization of a new generation of ultrathin, efficient, and tailorable optical devices that operate across a broad spectral range and potentially at the quantum limit, enabling new technologies in quantum photonics, secure optical communication, and next-generation sensing platforms.

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

Over the course of the project, METANEXT has successfully transformed its core conceptual ideas into a series of demonstrable photonic technologies. The initial phase focused on developing a reproducible and robust nanofabrication methodology tailored for atomically layered materials. This new approach effectively addressed long-standing challenges associated with patterning van der Waals heterostructures, thereby enabling the high-fidelity fabrication of complex nanostructures. This advance laid the essential groundwork for the subsequent experimental milestones.

Building on this foundation, the project achieved one of its central goals: the first-ever experimental realization of a van der Waals heterostructure metasurface exhibiting strong light-matter coupling at room temperature. This was accomplished by vertically stacking different 2D materials and directly etching resonant nanostructure into the heterostructure itself, forming an ultrathin optical cavity. This resulting platform demonstrated exceptional efficiency, enabling strong coupling phenomena at significantly reduced power threshold (orders of magnitude lower than those required by conventional architectures), marking a critical step toward practical device integration.

To accelerate its discovery and optimization processes, METANEXT introduced the concept of dual-gradient metasurfaces, an innovative "spectrometer-on-a-chip" platform. This approach allowed for the simultaneous interrogation of thousands of different nanophotonics designs on a single chip, drastically improving throughput and facilitating rapid identification of optimal resonator geometries for boosting light-matter interaction.

Finally, significant progress was made toward quantum photonics applications. The metasurfaces developed within the project framework were shown to enhance the spontaneous emission rate of quantum defects embedded in 2D materials, and to provide precise control over the chiral properties of emitted light. Such capabilities constitute essential prerequisites for the development of next-generation chiral light sources, including quantum-compatible circularly polarized lasers.

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)

The METANEXT project has delivered several key innovations that significantly advance the state of the art in nanophotonics and materials science. Foremost among these is the demonstration of van der Waals heterostructure metasurfaces (vdW-HM), which constitutes a paradigm shift in the design of photonic systems. Whereas previous approaches positioned two-dimensional (2D) materials in the vicinity of prefabricated metasurfaces, our methodology directly constructs the photonic architecture from the 2D materials themselves. This enables unprecedented control over light-matter interactions and led to the observation that strong coupling can be saturated with power levels up to three orders of magnitude lower than in prior systems. Such ultra-low-power operation renders these devices highly promising for integration into on-chip quantum devices and photonic circuitry.

A second major contribution is the development of dual-gradient metasurface. While single-gradient metasurfaces have been explored previously, the feasibility of independently controlling two optical parameters (i.e. resonance wavelength and quality factor) within a single device was previously unproven. METANEXT has successfully realized this concept, achieving a mode density that approached the theoretical limit for metasurfaces in a compact footprint. This platform thus offers a powerful new tool for fundamental and applied research, with potential to accelerate discoveries in material characterization, photocatalysis, nonlinear optics, and molecular sensing.

To ensure the further uptake of these results, several key needs should be met. (1) The platform should be extended to additional 2D materials in order to uncover new physical phenomena and enable the realization of fully operational quantum photonic devices, such as on-demand single-photon emitters and chiral laser sources. (2) Scalable fabrication processes should be explored to facilitate the transition from laboratory-scale demonstrations to wafer-level manufacturing, which will be necessary for commercial viability and integration with complementary metal-oxide-semiconductor (CMOS) technology. (3) The project must establish effective pathways for knowledge transfer and collaboration with industrial stakeholders in quantum technologies, sensing, and telecommunications, thereby facilitating the translation of these disruptive device concepts into practical, real-world applications. METANEXT is already committed to a multi-2D-material approach and possible large-scale fabrication approaches, and we will leverage the continuing dissemination of the project results in high-impact publications as well as at conferences and trade fairs to effectively establish links with industrial partners.