Picometers and Attoseconds: The Dimensions of Atoms and Light
Atoms and electrons are the two central constituents of all materials in our surroundings, but their movements and reaction paths are so small and so fast that observation is close to impossible. By unifying electron microscopy with attosecond/femtosecond laser technology, we combine the awesome spatial resolution of modern electron microscopes with the spectacular time resolution that is offered by the cycle period of light. In this way, light-matter interaction and material transformations become visible on atomic dimensions in space and time.
Ultrafast Electron Microscopy and Diffraction
Whenever something changes, atoms and electrons have to move from initial to final configurations. Ultrafast electron microscopy and diffraction allow to "make a movie" of atomic-scale movements, by simultaneously providing picometer resolution and femtosecond/attosecond timing. A laser pulse (or its field cycles) is used to initiate/push the dynamics of interest, and ultrashort electron pulses are diffracted to visualize the atomic-scale structures as they evolve in time. The materials that we work on include magnetic materials, molecular crystals, metamaterials, surfaces, nanostructures, photonic circuitry, eventually biomolecules, and many more. Essential for our ultrafast electron microscopy is the use of single-electron pulses without space-charge effects. Our ultrashort electron pulses are therefore quantum objects - a research topic on its own.
Attosecond Lightwave Electrodynamics and Metamaterials
The all-optical control of electron beams with the cycles of terahertz radiation or laser light allows to reshape the electron into pulses of femtosecond and attosecond duration. These attosecond electron pulses offer direct four-dimensional visualization of charge density dynamics with combined spatial and temporal resolution for investigating the motions of electron density in photonic circuitry, metamaterials, nonlinear optical materials, photonic devices, molecular crystals, superconductors, and many others.