Attosecond Space–Time Imaging with Electron Microscopy and Diffraction

The first step of most light-matter interactions is a field-driven motion of electron density in and around the atoms of a material. Fully visualizing such dynamics and its consequences for the macroscopic functionality of a material, therefore, requires atomic resolution in space and sub-light-cycle resolution in time. Here, we review our latest progress with attosecond space–time imaging by using attosecond electron pulses in diffraction and microscopy. We start with a brief review of recent technological advancements for the temporal compression of ultrashort electron pulses with radio-frequency waves, terahertz pulses and now optical field cycles. We then report on the light-wave control of electron beams at thin metallic or dielectric membranes, which form the basis of attosecond electron imaging in our laboratory. We report the first demonstrations of attosecond electron diffraction and microscopy in proof-of-principle experiment that reveal an upper limit for the delays associated with electron-crystal scattering and visualize the oscillations and propagation of a traveling light wave on a nanometer-thick membrane. These unprecedented space–time resolutions provided by attosecond electron microscopy and diffraction now enable to capture the dynamics of electrons inside of atoms, molecules, crystals or nanostructures as a function of space and time.