Physics and applications of a novel nanometer-sized femtosecond electron souce

点击翻译按钮获取中文摘要

The project aims at understanding and controlling highly nonlinear photoemission processes at sharp metallic needles triggered by ultrashort pulses of near-, mid- and far-infrared radiation. In the first funding phase of this project, we demonstrated access to a new regime in photoemission from nanostructures, in which the electrons’ kinetic energies are no longer determined by the photon energy and the work function alone, but rather by the interaction of the electrons with the locally enhanced optical near-field at the apex of the needles. In the second funding phase, a main objective lies in the manipulation of these processes by a number of means, including (i) multiple pulses of varying wavelength, such as THz pulses, (ii) control over the carrier-envelope phase and (iii) gating of electron pulses by means of surface plasmon polariton fields. Using these approaches, we plan to reach a previously unachieved level of control over the femtosecond and attosecond electron dynamics at this nanostructure, which will manifest itself in modifications of the angular and kinetic energy distributions of electrons emitted from the excitation region. In addition to the study of fundamental properties of the emission and acceleration process, we will extend the efforts regarding the application of this pulsed electron source with high spatial coherence. Specifically, we will experiment with spatially resolving electron energy loss spectroscopy on nanowires and multilayer graphene in a point-projection geometry.