LMU Munich develops ultrathin components that capture light better

28 May 2025

Atomically layered systems promise smaller, more efficient photonic parts.

Researchers at Ludwig Maximilian University, Munich, Germany, are developing ultrathin optical components made of atomically layered systems, which capture light much better than previous materials. They say that this could “pave the way for considerably smaller and more efficient photonic components.”

The team, led by Andreas Tittl, Professor of Experimental Physics at LMU, have developed a method that permits the manufacture of extremely thin optical components that react strongly to even comparatively weak light.

“In the future, these thin components could pave the way for tiny, more sensitive sensors, more energy-efficient computer components, and faster optical communication,” said Tittl. The Functional Nano team has reported on their method in Nature Photonics.

The nanophotonic materials used are based on metasurfaces, which have regular patterns generally smaller than the wavelengths of light. With suitable metasurfaces it is possible to precisely control light beams.

In what they describe as “a first”, the researchers led by Tittl have now integrated the concept of metasurfaces into multilayered 2D materials whose individual layers can consist of just one or two, atomic sheets. “The best known 2D material is graphene, but actually there are quite a number of other ones now available,” said Tittl.

“You can obtain these materials in crystal form, remove individual layers under the microscope, and stack them like paper. You can precisely control their atomic arrangement and obtain materials with strong in-plain covalent bonding and weak interlayer interactions (“van der Waals materials”, which are an important focus of modern materials research).

Combining concepts

“Before now, the literature stopped at macroscopic stacks of multiple 2D materials,” said Tittl. His group utilized an additional nanolithographic process to add further structural parameters to the van der Waals stack, which amplify the light-matter interactions as on a metasurface.

“So, instead of placing 2D materials on separate, ready-made nanostructures or using bulky external optical resonators, we worked the resonance structure directly into the vdW stack,” said Tittl. The researchers named the components created in this way “van der Waals heterostructure metasurfaces” – or vdW-HMs for short.

In collaboration with researchers from a group led by Prof. Achim Hartschuh at the Technical University of Munich, the LMU team packed an individual semiconducting layer of tungsten disulfide, WS₂, between several protective layers of hexagonal boron nitride. Using a lithographic technique, the researchers then worked periodic structures into this material stack, with which light interacts efficiently.

To obtain the highest possible interaction between light and matter and control unwanted diffraction, the researchers carried out theoretical modeling and simulation. They were thus able to optimize the vdW-HMs and ended up with nanophotonic components that reacted even to light intensities over 1,000 times lower than previously reported.

“Essentially, we’ve developed ultrathin resonators that capture light very efficiently so that we can use it,” said Luca Sortino, a member of Tittl’s team and lead author of the study.

“We’ve now got a toolkit for combining the two materials science concepts and extending this model to many other 2D materials,” said Sortino. So it would be possible to develop various nanophotonic components with customized optoelectronic characteristics. The researchers are now planning to further investigate this potential.