Metamaterials, engineered at the nanoscale, exhibit unique properties not found in naturally occurring materials. These properties arise from their nanoscale building blocks, which, until now, have been challenging to observe directly due to their size being smaller than the wavelength of light. Scientists from the Fritz Haber Institute in Berlin overcome this limitation by employing a new microscopy technique that can simultaneously reveal both the nano and macro structures of these materials.

The key finding of this research is a methodological breakthrough that enables the visuali­zation of structures previously too small to be seen with tradi­tional microscopy. By using light in innovative ways, the scientists have discovered how to trap one color of light within the structure, and use a mixing with a second color that can leave the structure to visualize this trapped light. This trick reveals the hidden world of nanoscale optical meta­materials.

This achievement is the result of more than five years of dedicated research and develop­ment, utilizing the unique features of the Free Electron Laser (FEL) at the Fritz Haber Institute. This type of microscopy is particularly special because it allows for a deeper understanding of meta­surfaces, paving the way for advancements in techno­logies such as lens design, with the ultimate goal of creating flatter, more efficient optical devices.

By enhancing our under­standing of meta­surfaces, this research opens the door to the development of novel light sources and the design of coherent thermal light sources. “We are just at the beginning,” states the research team, “but the implications of our work for the field of flat optics and beyond are immense. Our technique not only allows us to see the complete per­formance of these nano­structures but also to improve upon them, shrinking 3D optics down to 2D, and making everything smaller and flatter.” (Source: FHI)

Reference: R. Niemann et al.: Spectroscopic and Interferometric Sum-Frequency Imaging of Strongly Coupled Phonon Polaritons in SiC Metasurfaces, Adv. Mat. 36, 2312507 (2024); DOI: 10.1002/adma.202312507

Link: Lattice Dynamics Group, Fritz-Haber-Institute, Berlin, Germany