1) Theoretical modelling and full experimental characterization of an all-optical electron modulator
We have demonstrated full phase-space characterization of light-induced modification of the electron phase and amplitude profiles in space (nm), time (sub-fs), energy (sub-eV) and momentum (μm^-1). We have performed measurements of light-induced transverse and longitudinal electron shaping with a Spatial Light Modulator. In parallel we have performed design, optical characterization, and nanofabrication of a focusing metalens to be inserted in the PELM.
2) Design, realization, installation, operation and characterization of Photonic free-ELectron Modulator (PELM) devices at EPFL, TECHNION and UNIMIB.
We have worked at the design, prototype realization, mechanical installation, operation, commissioning and characterization of the PELM devices in the UTEM at TECHNION, EPFL and UNIMIB. We have successfully operated 3 photonics electron modulators (at the pre-CL stage, at the sample-stage, and at the post-CL stage). Finally, we have designed further upgrades to the PELM devices and performed a full performance optimization analysis.
3) Implementation of the Ramsey Holographic Imaging (RHI) method
We have developed RHI by using phase-modulated free-electron pulses in a homodyne detection scheme. We have demonstrated simultaneous phase-resolved dynamics of near-field in test nanostructures, which is not possible using current approaches. Finally, we have applied our method to the investigation of quantum materials, and specifically to the phase dynamics of Berry singularities in 2D hexagonal boron nitride, as well as to the coherent control of Skyrmions lattice in multiferroic Cu2OSeO3.
4) Implementation of the Electron Single Pixel Imaging (ESPI) method
We have performed ESPI reconstruction using optically-modulated electron pulses on several type of samples in a 4D-STEM mode where the SLM-shaped light is used in conjunction with a momentum-resolved analysis. We have tested our method on several nanofabricated structures as well as MAX phase nanoparticles on a lateral scale of 1-10 μm and sub-ps time scale. Finally, we have performed ultrafast structural analysis of MAX nanoparticles in a pump-probe scheme with transversely-modulated electrons for improving the beam lateral coherence.
5) Implementation of the Quantum Cathodoluminescence (Q-CL) and Enhanced Electron Imaging Contrast (EEIC) methods
We have designed, realized, and operated a modified TEM sample holder for measuring coherent and incoherent light emission from quantum emitters. However, we have not been able to observe a level of coherent light emission needed to demonstrate superradiance. Nevertheless, we developed a contingency plan thanks to which we demonstrated Enhanced Electron Imaging Contrast of nanostructures via photon-mediated or plasma-mediated interactions with enhancement factors ranging from 50 to 800 %. We have then performed experiments on lipo-gold nanoparticles and on HeLa cells incubated with lipo-gold nanoparticles, showing enhanced contrast of 30 – 40 % with simultaneous μm-spatial and sub-ps temporal resolutions.
6) Dissemination & communication
We have also focused on the outreach strategies via social media presence and engagement events. We have organized: 3 international conferences, 13 workshop/seminars, 5 outreach events, 5 science bashes. The partners have attended > 80 international events and published over 40 papers.
