In this seminar, we will review the recent advances in fs-transmission electron microscopy. The design and implementation of a fs-resolved transmission electron microscope will be briefly introduced and its overall performance in terms of time, energy and spatial resolution will be presented. Thanks to this technology, the direct imaging of light-induced surface plasmon polaritons in nanostructures is enabled. When electrons and photons are overlapped spatially and temporally on a nanostructure, the evanescent field photoinduced at the edges of the latter interacts with the electrons allowing them to absorb and emit photons from the pump laser beam. This results in sideband peaks spaced by an energy corresponding to the pump photon energy on both the energy gain and loss sides of the elastic electrons peak. By selecting one or more of these sidebands via energy filtered imaging, snapshots of the surface plasmon polaritons can be taken. Such a technique is called Photon Induced Near Field Electron Microscopy (PINEM). By controlling the properties of light excitation, its energy, polarization and intensity, the distribution of the field around a given nanostructure can be controlled, providing a unique tool for the characterization and manipulation of optoelectronic circuits. The life-time of the surface plasmon polariton waves on metallic materials is found to be ultrafast, comparable to the laser excitation pulse duration (100 fs), and reveals information about the surface morphology and its electronic properties.
This work was supported by an ERC starting grant.