Hyperbolic phonon polaritons (HPhPs) are hybrid light–matter waves that can confine infrared electromagnetic fields to spatial scales far below the corresponding free-space wavelength. Controlling HPhPs on femtosecond timescales could provide a foundation for future ultrafast and ultracompact nanophotonic devices. However, directly imaging such ultrafast dynamics has remained challenging because HPhPs are strongly dispersive and their wavelength changes markedly with frequency. Broadband femtosecond laser pulses therefore excite HPhPs over a range of wavelengths, causing their interference patterns to overlap and wash out in real-space images. In this study, researchers developed an ultrafast infrared near-field optical microscopy technique that combines nanoscale spatial resolution and an approximately 150-femtosecond temporal resolution with a spectral resolution of about 10 cm⁻¹. By using a diffraction grating to spectrally resolve the light scattered from the microscope tip before detection, the technique enables frequency-selective imaging without sacrificing ultrafast time resolution. Applying the new technique to a van der Waals heterostructure composed of tungsten disulfide (WS₂) and hexagonal boron nitride (hBN), the researchers revealed how photoexcited charge carriers generated in WS₂ transiently modulate HPhPs propagating in the adjacent hBN. The researchers observed changes in the HPhP electric-field amplitude and, in structures containing a relatively thick WS₂ layer, a change in the HPhP wavelength. The researchers say, “The results establish a new platform for observing and controlling nanoscale light propagation on femtosecond timescales, opening new opportunities for ultrafast nanophotonics”.

Researchers have developed fluorescent molecules that permit imaging how DNA is packaged inside living cells at unprecedented resolution, and in preserved cells, close to the width of the double helix itself. The advance raises the possibility that one day they could train an AI to look at how DNA occupies three-dimensional space inside cells for diagnosing and treating cancer and other types of conditions.

With funding from the Federal Ministry of Research, Technology and Space (BMFTR), the new project SIBAF (Supraleitender Ionenbeschleuniger als BAsistechnologie für die Fusionsforschung) will establish a unique accelerator-based infrastructure for the rapid qualification of advanced materials for future fusion power plants. As part of the funding program “Basistechnologien für die Fusion – auf dem Weg zu einem Fusionskraftwerk” (Basic technologies for fusion – on the path to a fusion power plant), SIBAF will receive €9.7 million over three years, of which €8.1 million will support activities at the GSI Helmholtzzentrum für Schwerionenforschung and the international accelerator center FAIR, currently under construction. Alongside GSI, which coordinates the project, Goethe University Frankfurt is the project partner.

Venus appears pale yellow in visible light, but ultraviolet images reveal dramatic dark and bright patterns moving with the planet’s upper sulfuric acid clouds. Scientists have known about these markings for roughly a century, yet the chemical identity of the material responsible—the “unknown absorber”—remains unresolved.